EYE CARE

In an effort to supply information to consumers on better eye health, we are proud to provide general eye care information. In this section, we will explain how the human eye works and define some of the most common vision conditions. We've also included a "did you know" section that focuses on common concerns and questions about eye care and contact lenses.While this information is helpful, it should not be construed as medical advice. For more detailed explanation on any of the topics in this section, please consult your eye care professional.

The Human EyeAnatomy of the eyeA human eye gives the sharpest vision when it is perfectly spherical, that is, round like a basketball. Distortion occurs when the eyeball is too short from front to back (Hyperopia) or too long (Myopia), or the curvature of the cornea is irregular, egg shaped rather than a perfect sphere (astigmatism).
How the eye worksLight from object A is focused by the cornea and crystalline lens to form an upside-down image on the light-sensitive cells of the retina. Information is transmitted as impulses from these cells to the brain via the optic nerve. The quantity of light entering the eye is regulated by the iris. The pupil is the variable-sized black circular opening in the center of the iris.
This is an example of normal spherical vision.Please note: The brain re-interperets the image, making it appear right-side up.
Did You Know?Here you will find answers to some of the most common eye care questions and concerns. While this information is insightful, we ask that you consult your eye care professional about any concerns you have with about your vision. This should not be construed as medical advice.
Are contacts a good fit for you?Most people with vision conditions have no problem wearing contact lenses. And, with new materials, replacement schedules and lens care technologies, wearing contact lenses has never been easier.
However, you may have difficulty wearing lenses, if: • Your eyes are irritated by allergies. • Your work environment hosts large quantities of dust or chemicals. • You suffer from uncontrollable diabetes, severe arthritis in your hands, or an overactive thyroid. • Your eyes are overly dry due to medications or pregnancy. See your eye care professional to find out if contact lenses are right for you.
Children need regular eye examsOf children between the ages of 5 and 12, one in four suffer from an undiagnosed vision problem that effects their educational performance. Because children often have no way of knowing if their vision is poor, it is much harder to detect the problem. It is recommended that all children have their eyes examined at age 4. If there is a family history of eye conditions, it is recommend that their eyes be examined by the age of three. Early detection is the key to good vision and vision problems often respond favorable during the growth and development of a child’s visual system.
Signs that your child may have a vision problem• Squinting, rubbing or blinking the eyes a lot• Having trouble seeing the blackboard at school• Using a finger as a place mark when reading• Holding head at an awkward angle when reading• Closing or covering one eye to focus• Holding reading materials close to face• Having red or crusty eyes
Adults need regular eye exams, tooIdeally, you should have your eyes examined every year. Routine eye exams can detect early signs of vision conditions, allowing for fast treatment of most problems. Eye exams can also reveal serious and often times, hidden medical conditions like high blood pressure, diabetes, inflammations and infections.
A typical eye examQuick and painless, routine eye exams ensure good, healthy vision. Before your exam, your eye care professional will ask you about your health history and your family history, whether you've experienced any eye trouble, and ask you to describe your work and lifestyle. Then, he/she will test your eyes: checking for eye movement, peripheral vision and color blindness, administering a glaucoma test and determining the health of your optic nerve and retina.
Computer use and your eyesMany in our workforce spend the majority of their work day in front of a computer screen. And, nearly 90% of those working at a video display terminal experienced some form of vision problems as a result. Symptoms that are related to computer use are:• Difficulty focusing after working at a computer• Eye strain or fatigue• Headaches• Dry, itchy and/or irritated eyesThere are also environmental factors that increase computer-related eye strain:• Bright lights in your peripheral vision can be distracting.• Reflected light on your computer screen can cause a glare, decreasing the contrast of the screen character. To determine the cause of your symptoms, visit your eye care professional.
Lens Care TipsIMPORTANT NEWS:Evidence Suggests Proper Lens Care is Paramount to avoid Fungal Eye Infections• contact an eye care practitioner immediately if you experience eye pain, discharge, unusual redness, light sensitivity or sudden blurry vision.• choose a well-known, respected lens-care brand purchased from a reputable merchant to avoid unreliable, unregulated so-called "knock-off" products;• use the proper product to both clean and disinfect contact lenses (saline solutions and rewetting drops are not designed to disinfect lenses);• never reuse lens-care products; discard used product and only use fresh solution to ensure proper cleaning and disinfection;• carefully follow the care and cleaning regimens recommended by eye care practitioners and outlined in the patient information material that comes with the lens-care products; • carefully follow the contact lens wearing and replacement instructions recommended by eye care practitioners;Caring for your contact lenses is important to the health of your eyes. Lenses start to feel uncomfortable when protein deposits form on the lens’ surface. These deposits, found naturally in the tear fluid of your eyes, accumulate on the lens over a period of weeks and months.
You should always follow your eye care professional’s prescribed cleaning regimen. Failure to do so could result in red eye, pain, light sensitivity, tearing, or sudden changes in vision.
Glossary of Eye Care Terms
Age Related Macular Degeneration (ARMD): the breaking down of the macula, the back portion of the retina that is responsible for clear vision. There are two main types of ARMD. (1) Involutional ARMD (Dry ARMD) results in a slow, progressive loss of central vision (usually not beyond 20/200). There is currently no treatment. (2) Exudative (Wet ARMD) results in distorted or blurred vision caused by the growth of neovascular membrane in or near the macula. May be treated if diagnosed early without significant loss of central vision. (Ref: WebMD)
Amblyopia: a condition in which there is loss of vision for no apparent reason; the eye appears healthy, but vision is poor. This is also commonly known as "lazy eye”. The decreased vision is not correctable with optical devices. Patients with severe nutritional deprivation or vitamin B12 deficiency may experience simulated amblyopia. Complete recovery is possible with good diet and B vitamins, however, prolonged deficiency results in permanent loss of central vision. (Ref: WebMD)
Anisometropia: inequality of considerable degree in the refractive power of the two eyes, i.e. one eye is nearsighted and the other is farsighted).
Annual Replacement Lenses: conventional contact lenses that are replaced yearly.
Anterior uveitis: an inflammation of the middle layer of the eye, which includes the iris (colored part of the eye) and adjacent tissue, known as the ciliary body. If untreated, it can cause permanent damage and loss of vision from the development of glaucoma, cataract or retinal edema. Anterior uveitis can occur as a result of trauma to the eye, such as a blow or foreign body penetrating the eye. It can also be a complication of other eye disease, or it may be associated with general health problems such as rheumatoid arthritis, rubella and mumps. In most cases, there is no obvious underlying cause. Signs/symptoms may include a red, sore and inflamed eye, blurring of vision, sensitivity to light and a small pupil. (Ref: AOA)
Aphakic Lens: a lens designed to meet the needs of patients that have had their crystalline lens removed due to the development of cataracts.
Aspheric Lens: a not-quite-spherical lens that can improve contrast sensitivity and depth perception for borderline astigmats or emerging presbyopes. The power changes gradually, from the center to the edge of the lens.
Astigmatism: a condition caused by an irregularly shaped cornea (shaped more like a football than a baseball), resulting in two focal points causing light images to focus on two separate points in the eye and resulting in a blurred or distorted image.
Bifocal/Multifocal Lens: contains two or more viewing zones allowing for one to see distant, intermediate and near objects.
Blepharitis: a chronic or long term inflammation of the eyelids and eyelashes. It affects people of all ages. Among the most common causes of blepharitis are poor eyelid hygiene, excessive oil produced by the glands in the eyelid, a bacterial infection (often staphylococcal), or an allergic reaction. (Ref: AOA)
Cataracts: a painless, cloudy area in the lens of the eye. A cataract blocks the passage of light from the lens to the nerve layer (retina) at the back of the eye, and may cause vision problems. (Ref: WebMD) Cataracts can be surgically removed and replaced with an intraocular lens implant, restoring vision.
CMV Retinitis: CMV stands for Cytomegalovirus. This virus is a common source of infection in humans and generally lays dormant in the body without producing symptoms. When CMV attacks the cells in the retina, the condition is called CMV Retinitis. CMV Retinitis develops in 20% to 40% of patients with AIDS, making it the most common AIDS-related infection of the eye. In the early stages of CMV, you may not notice any change in vision, or you may notice "floating" particles or loss of peripheral vision. The condition often begins in one eye and then may appear in the other. If left untreated, the disease progresses and can cause serious loss of vision. CMV Retinitis is not associated with light sensitivity, pain, or redness of the eye.
Color Blindness or Color vision deficiency: A nonspecific term for congenital or acquired impairment of color discrimination, usually reds and greens but can also be blues and yellows. It seems that more males are affected, with 7% of males showing this deficiency, and only about 0.5% of females. Color vision deficiency is not a disease or degenerative condition, though occasionally an acquired color vision deficiency may be a symptom of other health problems. (Ref: Contact Lens Council)
Conjunctivitis (“pink eye”): often called "pink eye," it is an inflammation of the conjunctiva, the tissue that lines the inside of the eyelid and helps keep the eyelid and eyeball moist. Viruses, bacteria, irritating substances (shampoo, dirt, smoke, pool chlorine), sexually transmitted diseases (STDs), or allergens (substances that cause allergies) can all cause conjunctivitis. Pink eye caused by bacteria, viruses, or STDs can spread easily from person to person but is not a serious health risk if diagnosed promptly; allergic conjunctivitis is not contagious. (Ref: WebMD)
Contact Lens: a thin plastic lens designed to fit over the cornea, usually for the correction of refractive error. (Ref: Contact Lens Council)
Conventional Wear Contact Lens: a contact lens prescribed to be replaced after 12 months or as directed by the eye care practitioner.
Cornea: The transparent surface that covers the pupil and iris (like a watch crystal), and provides most of the eye's optical power. Contact lenses are worn over the corneal surface. (Ref: Contact Lens Council)
Corneal Dystrophy: abnormal corneal development resulting in structural or clarity defects. The cornea owes its transparency to the presence of a regular lattice structure of collagen fibers. Anything that affects this regularity, results in loss of the transparency, which is essential for good corneal function and health. Corneal dystrophies form a group of rare disorders that usually affect both eyes. They may be present at birth, but more frequently develop during adolescence and progress gradually throughout life. Some forms are mild, others severe. (Ref: RNIB website)
Crystalline Lens: The natural lens of the eye, a transparent structure suspended behind the iris. Focuses light rays on the retina and changes shape to change the focus of the eye for different distances. (Ref: Contact Lens Council)
Custom Toric Contact Lens: corrects mid to high levels of astigmatism and is generally manufactured on an Rx basis specifically for a particular individual.
Daily Wear Contact Lens: these lenses are intended to be worn during waking hours (less than 24 hours) and cleaned and disinfected each time they are removed from the eye.
Deposits: accumulation of substances, usually tear film components (protein), onto the contact lens surface and/or in the lens material. Types include protein, mucus, lipid, inorganic and soilant. (Ref: Contact Lens Council)
Depth Perception: the ability to judge the relative distance of objects and the spatial relationship of objects at different distances. (Ref: Contact Lens Council)
Diabetic Retinopathy: an eye disease caused by diabetes. Diabetes damages the small blood vessels in the retina, which can lead to vision loss. (Ref: WebMD)
Disinfecting Solution: an agent that kills surface bacteria and microorganisms. (Ref: Contact Lens Council)
Disposable Contact Lens: a single use lens. Defined by the U.S. Food and Drug Administration as a contact lens that is used one time and discarded. These can be either worn for a single day or, if they are also "extended wear" lenses, up to seven days, depending on the wearing schedule prescribed by the eye care professional. Any lens that is intended to be removed from the eye, cleaned, rinsed, disinfected, and reinserted does not qualify for inclusion in this category under the FDA definition. (Ref: Contact Lens Council)
Dry Eyes: Dry eye means that your eyes do not produce enough tears or that you produce tears which do not have the proper chemical composition. Often, dry eye is part of the natural aging process. It can also be caused by blinking or eyelid problems, medications like antihistamines, oral contraceptives and antidepressants, a dry climate, wind and dust, general health problems like arthritis or Sjogren's syndrome and chemical or thermal burns to your eyes. symptoms may include irritated, scratchy, dry, uncomfortable or red eyes, a burning sensation or feeling of something foreign in your eyes and blurred vision. Excessive dry eyes may damage eye tissue, scar your cornea (the front covering of your eyes) and impair vision and make contact lens wear difficult. (Ref: AOA)
Emmetropia: a condition generally known as “normal vision” where light rays from distant objects are focused on the retina so vision is sharp and clear (20/20). (Ref: Contact Lens Council)
Extended Wear Contact Lens: Contact lens designed to be worn round-the-clock for intervals of one to seven days. (Ref: Contact Lens Council)
Farsightedness (Hyperopia): People with farsightedness (hyperopia) have difficulty seeing objects close up. Farsightedness (Hyperopia) occurs when the eyeball is too short from front to back, or the eye's focusing mechanism is too weak, causing light rays to be focused behind, rather than on the retina. (Ref: Contact Lens Council)
Floaters and Spots: small, semi-transparent or cloudy specks or particles within the vitreous, the clear, jelly-like fluid that fills the inside of your eyes. They appear as specks of various shapes and sizes, threadlike strands or cobwebs. Since they are within your eyes, they move as your eyes move and seem to dart away when you try to look at them directly. Spots are often caused by small flecks of protein or other matter trapped during the formation of your eyes before birth. They can also result from deterioration of the vitreous fluid, due to aging; or from certain eye diseases or injuries.
Frequent and Planned Replacement Contact Lenses: see “Replacement Schedule”
Glaucoma: A condition in which the pressure inside the eye is elevated to a point that can damage the optic nerve and cause a loss of peripheral vision, or blindness. (Ref: Contact Lens Council)
Hard Contact Lens: also known as PMMA lenses, these traditional lenses are made from polymethylmethacrylate.
Hyperopia (Farsightedness): People with hyperopia (farsightedness) have difficulty seeing objects close up. Hyperopia (farsightedness) occurs when the eyeball is too short from front to back, or the eye's focusing mechanism is too weak, causing light rays to be focused behind, rather than on the retina. (Ref: Contact Lens Council)
Infections of the Eye: bacteria, viruses, and fungi are among the causes of inflammation. Every area of the eye is susceptible to attack by a large variety of organisms.
Intraocular Lens (IOL): a plastic lens implanted in place of the crystalline lens (either behind the cornea or behind the iris) during cataract surgery. (Ref: Contact Lens Council)
Iris: the colored portion of the eye that regulates the amount of light entering the eye by changing the size of the pupil.
J-1: the line on an eye chart that determines whether or not the patient needs glasses or contact lenses for reading.
Keratoconus: is a vision disorder that occurs when the normally round cornea (the front part of the eye) becomes thin and irregular (cone) shaped. This abnormal shape prevents the light entering the eye from being focused correctly on the retina and causes distortion of vision. (Ref: AOA)
LASIK: abbreviation for Laser-Assisted In Situ Keratomileusis. A kind of laser surgery designed to improve focus by altering the shape of the cornea. (Ref: Contact Lens Council)
Lazy Eye: a condition in which there is loss of vision for no apparent reason; the eye appears healthy, but vision is poor. This is also known as amblyopia. The decreased vision is not correctable with optical devices.
Monovision: a treatment technique that is often prescribed for people age 40 and over who are affected by presbyopia. Presbyopia occurs when, as part of the natural aging process, the eye’s crystalline lens loses its ability to bring close objects into clear focus. Monovision means wearing a contact lens for near vision on one eye and, if needed, a lens for distance vision on the other eye. (Ref: AOA)
Multifocal Contact Lens: also known as bifocal lens that contains two or more viewing zones allowing for one to see distant, intermediate and near objects.
Myopia (Nearsightedness): also known as nearsightedness, this inherited and sometimes stress-related condition occurs when the eyeball is too long or the cornea is too curved. The result is an inability to see at a distance.
Nearsightedness (Myopia): an inherited, sometimes stress-related condition that occurs when the eyeball is too long or the cornea is too curved. The result is an inability to see at a distance. The medical term for this condition is myopia.
Ophthalmologist: medical doctor (MD) uniquely trained in all aspects of eye care – medical, surgical, and optical - to diagnose and treat all disorders of the eye. (Ref: Contact Lens Council)
Optic Nerve: the two sensory nerves that join the eyes with the brain.
Optician: A paramedical professional who manufactures and dispenses eyeglasses and helps in the selection of frames. The optician may also dispense and/or fit contact lenses, depending on individual states’ licensing practices.
Optometrist (O.D.): State-licensed health care professional who diagnoses and treats eye health and vision problems. An OD can prescribe glasses, contact lenses, engage in low vision rehabilitation and vision therapy, has the authority to prescribe ophthalmic medications and perform certain surgical procedures. (Ref: Contact Lens Council)
Peripheral Vision: the ability to see to the left and the right of direct vision.
Photorefractive Keratotomy (PRK): a surgical procedure performed using an excimer laser to change the shape of the cornea to reduce vision problems. (Ref: Contact Lens Council)
Pink Eye (Conjunctivitis): an inflammation of the conjunctiva, the tissue that lines the inside of the eyelid and helps keep the eyelid and eyeball moist. Viruses, bacteria, irritating substances (shampoo, dirt, smoke, pool chlorine), sexually transmitted diseases (STDs), or allergens (substances that cause allergies) can all cause conjunctivitis. Pink eye caused by bacteria, viruses, or STDs can spread easily from person to person but is not a serious health risk if diagnosed promptly; allergic conjunctivitis is not contagious. (Ref: WebMD)
Planned Replacement: see “Replacement Schedule”
Presbyopia: a condition that occurs as the eye’s lens grows older and begins to lose some of the elasticity needed to switch focus between viewing near and far objects. Most people begin to experience the effects in their mid-forties. (Ref: Contact Lens Council)
Progressive Lenses: spectacle lenses that feature a continuous field of vision from up close to far away with no visible segment lines like traditional bifocal lenses.
Protein Deposits: a debris that is naturally produced by the eye.
Replacement Schedule: This is a general term used to refer to the schedule by which one should replace their contact lenses. In order to achieve comfortable, problem-free lens wear, most eye care practitioners will recommend lenses be changed every two weeks, monthly, or quarterly.
Retina: a thin nerve tissue in the back of the eye. It receives an image from the lens and transforms this image into electrical impulses that are carried by the optic nerve to the brain for interpretation. (Ref: Contact Lens Council) The central area of the retina (the macula) provides the clear, sharp central vision that you use for focusing on what is in front of you. The rest of the retina provides side (peripheral) vision. (Ref: WebMD)
Retinal Detachment: occurs when the sensory retina becomes separated (detached) from the retinal pigment epithelium (RPE) and the wall of the eye. Fluid from the eye flows into the space between the two layers, further separating them. (Ref: WebMD)
Retinitis pigmentosa (RP): is a group of inherited diseases that damage the light-sensitive rods and cones located in the retina, the back part of our eyes. Rods, which provide side (peripheral) and night vision, are affected more than the cones that provide color and clear central vision. Signs of RP usually appear during childhood or adolescence. The first sign is often night blindness followed by a slow loss of side vision. Over the years, the disease will cause further loss of side vision. As the disease develops, people with RP may often bump into chairs and other objects as side vision worsens and they only see in one direction – straight ahead. They see as if they are in a tunnel (thus the term tunnel vision).
Rigid Gas Permeable Lens: manufactured from silicon or fluoro-silicon acrylate base material, these lenses are used for irregular eye prescriptions.
Saline Solution: a salt solution that is available preserved or preservative free. It is used as a rinse prior to disinfection.
Snellen Chart: standardized test chart used to measure visual acuity. Visual acuity is expressed as a fraction (e.g. 20/20) in which the numerator denotes the testing distance and the denominator indicates the distance at which a person with normal eyesight can read the letters on the chart. For example, if the smallest letters that a person being tested can see are on the 20/40 line, it means a person with normal eyesight can see these same letters at a testing distance of 40 feet. (Ref: Contact Lens Council)
Soft Contact Lenses: these lenses are made from a flexible plastic know as a hydrogel. The lens becomes flexible as a result of absorbing approximately 40 to 70% its weight in water.
Spherical Aberration: blurry defect in optical elements that have a spherical surface, caused by differences in focal length causing light rays to fall on different locations of the macula preventing achievement of a common focus. (Ref: Encarta dictionary)
Spherical Contact Lenses: contact lenses that correct nearsightedness (myopia) and farsightedness (hyperopia).
Strabismus (crossed eyes): misaligned eyes that create the inability of one eye to obtain binocular vision with the fellow eye; usually due to imbalance of the muscles of the eyeball. Eyes may not only be crossed but could also point outward, upward or downward in the relaxed position. (Ref: Contact Lens Council; All About Vision)
Therapeutic Contact Lens: also known as a bandage lens, this lens is designed to aid in protecting and aiding a sick eye to heal. This unique lens is frequently combined with precise medication delivery schedules to heal the eye. (Ref: Contact Lens Council). It’s usually a large lens which blankets the cornea, retains its moisture and protects the surface of the cornea. Because the lens is well tolerated, it provides an effective and often times pain-relieving cover for the eye.
Tonometry: a standard eye test that determines the fluid pressure inside the eye. Elevated pressure is a possible sign of glaucoma. (Ref: Contact Lens Council)
Toric Contact Lens: designed to correct astigmatism by bearing two different optical powers at right angles to each other. (Ref: Contact Lens Council)
Trifocal Lens: lenses that correct vision for those with three focal lengths.
Visual Acuity: expressed as a fraction (e.g. 20/20) in which the numerator denotes the testing distance and the denominator indicates the distance at which a person with normal eyesight can read the letters on the chart.

ABOUT THE EYE

Some people liken the eye to a camera. As light passes through the lens, it is bent and transposed onto the eye’s film: the retina. The film is then ‘developed’ by the brain, becoming the image that we see. In order for an individual to have perfect vision, all components of the eye must be functioning properly. Otherwise, eye diseases and refractive errors can lead to impaired vision. Read the sections below to learn more about how the eye functions, its structures, and the eye diseases and refractive errors that result in imperfect vision.
How the Eye Functions
As light enters the eye, it first passes through the cornea, the clear outer portion of the eye. Because the cornea is curved, the light rays bend, allowing light to pass through the pupil to the lens. The iris, or colored part of the eye, regulates the amount of light that enters the eye with the ciliary muscles. These muscles cause the pupil to contract when exposed to excess light or to dilate when there is too little light.
When light hits the curved surface of the lens, it is refracted and brought into focus on the retina. The retina then turns the light into electrical energy. This energy passes through the optic nerve to the brain stem and finally into the occipital lobe, where it is converted into an image.
The Eye’s Structures
Cornea - The clear surface of the eye where light rays refract as they pass through to the pupil.
Iris - The colored part of the eye that controls the amount of light that passes through the pupil.
Pupil - An open space in the center of the iris where light passes through to the lens.
Lens - The part of the eye that refracts light to focus it properly on the retina.
Retina - The structure at the back of the eye that converts light rays into electrical energy that is transferred to the optic nerve.
Optic Nerve - The biological pathway to the brain stem, which forwards electrical energy to the occipital lobe.
Occipital Lobe - The part of the brain that converts electrical energy into an image.
Eye Diseases and Refractive Errors
The process described above occurs flawlessly in people with 20/20 vision. However, vision can be impaired when the shape of the eye is irregular or when the light rays do not focus properly on the retina. These flaws are known as refractive errors. Imperfect vision can also occur as a result of various eye diseases. Learn more about the refractive errors and eye diseases that cause vision problems.
Refractive Errors
Refractive errors can be treated with LASIK surgery, custom LASIK, or other laser vision correction procedures, including PRK and LASEK. The following refractive errors can impair vision:
Nearsightedness (myopia) - Nearsighted vision is caused by an irregularly shaped cornea that results in light focusing in front of the retina, rather than directly on the retina. People who are nearsighted have difficulty seeing objects at a distance.
Farsightedness (hyperopia) - Farsighted vision is caused by an irregularly shaped cornea that results in light focusing behind the retina instead of directly on the retina. People who are farsighted have difficulty seeing nearby objects.
Astigmatism - The most common of all eye disorders, astigmatism is a condition in which the eyeball is shaped more like a football than its naturally spherical shape. This odd shape causes light to focus on two points of the retina, rather than one.
Presbyopia - Presbyopia occurs when the lens of the eye becomes less flexible, necessitating the use of reading glasses for near vision. Specifically, the lens becomes stiffer, and the muscles that control the lens become weaker, hindering its ability to bend and flatten in order to focus light on the retina.
Eye Diseases
Cataracts - A cataract is a condition characterized by a clouding of the eye’s natural lens. This clouding occurs when protein begins to clump together in the lens.
Glaucoma - Glaucoma is an eye disease that occurs when elevated intraocular pressure (IOP) causes damage to the optic nerve.
Macular degeneration - Macular degeneration is a degenerative eye disease that is characterized by a loss of central vision. It occurs when the macula (a tiny area on the retina) becomes damaged.
Diabetic retinopathy - Diabetic retinopathy is a degenerative eye disease that occurs in patients with diabetes and is characterized by abnormal blood vessel growth. This can eventually lead to a detached retina and blindness.

MYOPIA TREATMENT

Myopia treatment has come a long way with the advent of refractive surgery. Now many nearsighted patients are able to reduce or even eliminate their dependence on glasses or contact lenses. Learn more about the treatment options available for patients with myopia by reading the sections below.
Glasses and Contact Lenses
Of all the available myopia treatments, wearing glasses or contact lenses is the least invasive, longest-standing, and most adjustable option. Because children and teens are likely to have changes in their refractive error as they grow, glasses or contact lenses are generally recommended for younger myopia patients. A prescription for corrective lenses can be easily changed as needed and there is a lower risk of damage or infection of the eye than with refractive surgery.
LASIK
The most popular and well-known type of refractive surgery, LASIK involves making a thin flap on the surface of the cornea and reshaping the corneal tissue beneath with a laser to correct the refractive error. The flap is then folded back into place to protect the newly reshaped cornea. Newer technologies that allow doctors to adjust for the unique characteristics of an individual eye have given rise to the term custom LASIK. Benefits of LASIK include a rapid recovery time, high success rate, and the ability to correct a wider range of refractive errors than other types of surgery. Possible side effects include dry eye, glare, and halos around lights at night. LASIK is an effective myopia treatment for many, but some people are not good candidates for the surgery, including those without a stable refractive error, pregnant or nursing women, and people with thin corneas.
PRK
Another type of refractive surgery that is an effective myopia treatment is PRK, or photorefractive keratectomy. Like LASIK and other refractive surgeries, PRK uses a laser to reshape the cornea so light focuses properly on the retina rather than in front of it. Instead of creating a corneal flap, however, PRK involves removing the epithelial layer of cells from the cornea with an alcohol solution. This makes the procedure ideal for those who may not be good candidates for LASIK due to thin corneas. It does, however, require a longer healing time, and patients will need to keep their eyes protected until the epithelial cells regenerate.
LASEK
LASEK is a relatively new type of refractive surgery. It involves weakening the epithelial cells at the outermost layer of the cornea with an alcohol solution and folding them back to create a much thinner corneal flap than is made with LASIK. This allows the laser reshaping to be applied to a much thicker portion of the cornea, while retaining the protective qualities of a corneal flap. As a myopia treatment, this procedure can safely correct higher degrees of nearsightedness than PRK, but is suitable for people with thinner corneas that cannot have LASIK. There is some possibility that the epithelial cells may not hold up well enough to be replaced, in which case the procedure becomes a PRK treatment instead.
Epi-LASIK
Epi-LASIK is similar to LASEK in that it involves the creation of a very thin, epithelial flap rather than the thicker type of flap created with LASIK. Epi-LASIK, however, uses a super-fine blade to push the epithelial cells aside, instead of weakening them with alcohol. This reduces the chance of the cells breaking down and becoming too unstable to be replaced. Epi-LASIK may be an effective myopia treatment for those who are not good candidates for other types of refractive surgery.
Implantable Contact Lenses
A different kind of myopia treatment altogether, implantable contact lenses are surgically implanted in the eye to correct refractive errors and improve vision. Visian ICLs™ are placed between the iris and the eye’s natural lens, while Verisyse IOLs™ are placed in front of the iris, just behind the cornea. Neither type can be seen nor felt once it is in place.
Benefits of implantable lenses include freedom from the hassle of glasses or traditional contact lenses, rapid healing time, and reversibility in the case of eye changes or complications. As with all surgery, there is some risk of infection or inflammation.
Intacs®
Intacs® are a unique type of myopia treatment for people who are mildly nearsighted. Prescription inserts that are surgically placed around the edge of the cornea, Intacs® are designed to gently push the natural cornea into a more optimal shape for clear vision. The procedure to place them is quick and essentially painless and most people experience improved vision the very next day. Unlike having refractive surgery, receiving Intacs® does not require natural corneal tissue to be removed and is entirely reversible.

PRESCRIPTION EYEGLASSES

With new advances in medical technology designed to reduce your dependence on prescription eyeglasses, eyewear is a choice and not a burden. Wearing eyeglasses is fun and a great way to make a personal statement. We’ve included some helpful tips on selecting a pair of glasses that will look great, feel comfortable, and last you well into the future.
Selecting Your Frames
Eyeglasses, both wardrobe accessory and practical tool, come in a dizzying array of shapes and sizes. As lens technology has advanced over the years, so too has frame fashion, both in style and functionality. Sports enthusiasts can purchase frames that are designed to stay put during a sprint or a swim. Business professionals can purchase frames in a range of sleek, sophisticated styles. For a less noticeable pair of prescription eyeglasses, you can choose rimless eyewear. Ladies who are fashion forward can treat themselves to an ever-widening array of fun eyewear shapes and sizes as well as a variety of eyeglass frame hues.
Here are some general tips to help you find the set of eyeglass frames that perfectly suits your look and lifestyle.
Shape of the Frames
The shape of the frame you select for your prescription eyeglasses should complement the shape of your face as well as your facial features. For the best visual effect, the shape of the frames should contrast with your face shape. The positive aspects of your face shape can be emphasized and the negative aspects can be de-emphasized by selecting the right set of eyeglass frames. An overly round face can appear thinner through the use of a frame with sharper angles, such as a square shape. Faces that are more triangular in shape can achieve a balanced look with the right set of frames. For a base-down triangle face, try color accents on the top half of the frames or a cat-eye shape. People with a base-up triangle face can try light colors and materials or rimless eyeglasses. Narrow frame styles can help soften a very wide and strong jaw line.
Regardless of your face shape, be sure to purchase prescription eyeglasses that are the proper scale in relation to your face. Eyeglasses that are overly large will overwhelm a more delicate bone structure, whereas eye glasses that are excessively dainty will make your eyes look a bit on the beady side. The sales representative at your local frames outlet can likely steer you in the right direction in this regard.
Color of the Frames
To further customize your prescription eyeglasses, the base color of your skin, hair, and eyes should match the base color of your frames. Cosmetologists cite two basic ways to classify a person’s hair and facial features: Everyone’s features conform to either a warm (yellow-based) or cool (blue-based) color palette, and most people’s features are fairly uniform in their classification in relation to each other. Matching the base color of your facial features to the base color of your frames simply means that if you have a warm face, your eyeglasses should be framed by a warm color; and if you have a cool face, your eyeglasses should be framed by a cool color.
Consulting the person behind the makeup counter at your local department store is an easy way to get advice on whether or not you have a warm or cool skin tone. Anyone with experience working with cosmetic facial products should be able to ascertain your classification with relative ease. Olive skin is the only tricky complexion. A mixture of blue and yellow, olive skin is usually considered a cool complexion color.
For hair color, strawberry blond, platinum, blue-black, white, salt-and-pepper, and “dishwater” brown are all cool colors. By contrast, golden blond, flat black, brown-gold, “carrot,” and “dirty” gray are all warm colors.
Eye color is the hardest to classify because it has the greatest range of hue of the three criteria. Whether your eye color is considered warm or cool depends not only on the particular color of your eyes, but also on how light or dark your eyes are and how uniformly the color is spread throughout your iris. An experienced cosmetologist would likely be able to tell you how your eyes classify, but unless the color is very intense (such as deep blue), this is probably the least important criterion for eye frame color selection.
Once you have determined whether you classify as mostly warm or mostly cool, you will have successfully narrowed your options, but there will still be quite a few colors to choose from.
Size of the Frames
Selecting the right size frames for your face isn’t just an issue of aesthetics. Prescription eyeglasses need to fit well in order to be comfortable and, particularly in the case of bifocals, function the way they are meant to.
Professional frame manufacturers refer to the arms on a pair of glasses (the parts that goes behind your ear) as the temples. In order to prevent the temples from digging uncomfortably into the sides of your head, you need to select a pair of frames that are sufficiently wide. The edge of the frames should protrude slightly beyond your head in order for the temples to extend back to your ears without touching your face too much. Otherwise, they might pinch slightly. The curve at the end of the temple should be able to pass over the ear without pressing down directly upon it. Be sure to try on different frames before purchasing a pair, paying special attention to the comfort of the temples in order to select the best length.
The glasses should also sit comfortably on your nose without pinching. This is especially important if the frames you are considering do not have an adjustable nose pad. Most nose pads are composed mainly of silicone; however, vinyl nose pads are available in various sizes for those with skin sensitive to silicone.
Be sure to bend over when you are trying on your new frames. This is the best test to determine if you have selected the proper size. A well-fitting pair of glasses will stay put without pressing too hard against your face.
Most people’s eyeglass frames last for a long time, particularly frames made out of a durable material such as titanium. Taking the time to choose a comfortable pair of frames that are the proper size and shape for your face can save you a lot of headaches later. Your eyeglasses may be with you for some time, so be sure to select them carefully.
Prescription Eyeglasses
If you have thought carefully about what lifestyle needs your glasses will have to accommodate and have purchased a durable set of frames, then you will probably only need to purchase a new set of eyeglasses when your prescription changes. Many people like to purchase a new set of glasses once or twice every 10 years or so simply to update their look. Scratch-resistant lens coating and shatter-resistant lenses are two product options that can easily extend the life of your glasses. Spring hinges are another good feature for improving the durability of your prescription eyeglasses.
If you don’t like the idea of regularly purchasing new eyeglass frames, avoid selecting very trendy eyewear. The hot fashion of today will become the fashion faux pas of tomorrow, and you may be stuck feeling behind the times while you wait for your look to come around again.
Another good way to avoid the trouble of having to buy eyeglasses later on is to buy two or more pairs now. When purchasing new eyewear, take advantage of the two-for-one specials that many frame dealers periodically offer. Your life, like that of most people, is multifaceted. A single pair of glasses may not be able to be both sporty and professional, but with two or more pairs of glasses to fulfill your optical needs, buying a new pair of glasses every couple of years won’t be necessary.
If you wear prescription eyeglasses, it is very important that you regularly schedule a complete eye examination. There are two main reasons for this. First, your prescription can change gradually overtime, decreasing your quality of vision almost imperceptibly. This means that having your eyes examined by an eye care specialist is the only way to ensure you are getting the maximum amount of vision correction out your glasses. Second, people with pre-existing eye conditions, even minor ones, often have a greater likelihood of developing more severe eye disorders. In their earliest stages, these eye diseases have few to no visible symptoms. Thus, if you wait until you think there may be something wrong, it may be too late to effectively treat the eye disease without losing some quality in your vision.
If your prescription has been stable for a number of years and you do not have a personal or family history of serious eye disorders, then you can probably get away with going to the eye doctor every other year. Children and seniors should get their eyes tested at least once a year because they are more vulnerable to eye problems than people in other age groups. Those who have been treated in the past for serious eye conditions such as glaucoma or cataracts need to be examined by a trained ophthalmologist at least once a year, and more frequently if a doctor recommends it. Persons with severe diabetes have a higher risk of developing diabetic retinopathy and other anterior eye problems. Diabetics should consult their primary physician about how often they should see an ophthalmologist.
Prescription Sunglasses
Anyone who has ever attempted to attach a pair of clip-on sunglasses to their prescription eye glass frames knows why there is an ever-growing market for prescription sunglasses. Clip-on sunglasses are not one size fits all, and they don’t always stay on. Particularly during adverse weather conditions such as heavy winds, prescription sunglasses are easier on the eyes than the combination of contact lenses and sunglasses. They also tend to provide better protection from the sun’s rays.
Obtaining a pair of prescription sunglasses is easy. You can often purchase a pair at the same place you bought your prescription eye glasses. Some eyewear dealers even offer prescription sunglasses at a discount when you buy them in addition to a pair of regular eyeglasses.
Almost all styles and sizes of sunglass frames are compatible with prescription lens technology. The only exception is certain wraparound style sunglasses where the severe curve can distort the vision correction capacity of the lenses. High-index and polycarbonate are the two most popular and durable materials used to produce prescription sunglass lenses. Many lenses now have built-in UV protection. For those who regularly participate in outdoor water sports, polarized sunglass lenses are specifically calibrated to reduce the appearance of glare on water and wet surfaces. If the local eyewear dealer where you usually purchase your eyewear doesn’t carry prescription sunglasses, consider consulting your local optometrist for recommendations on manufacturers and dealers he or she trusts.
For those who spend a lot time outdoors but do not wish to purchase a second pair of prescription glasses for sun exposure, photochromic lenses are a great option. These lenses are specially designed to change color when exposed to different light levels. The lens becomes darker in bright light and lightens in lower light situations, such as indoors or during the night.
Reduce Your Dependency on Glasses
Thanks to the latest advances in eye care technology, there are a variety of ways to reduce or even eliminate your dependency on glasses.
The most economical means of maintaining good vision without using prescription eyeglasses is to switch to contact lenses. Modern contact lens technology has been around since the seventies and eighties. Contact lenses are not one size fits all, and they need to be prescribed by a qualified optometrist or ophthalmologist. Contact lenses are an effective means of vision correction for almost every eye prescription.
LASIK eye surgery is becoming increasingly popular as a method for producing permanent improvement in the clarity of a person’s vision without the use of glasses. Although classic LASIK is the most popular form of corneal tissue correction, there are other varieties of refractive eye surgery, including LASEK, Epi-LASIK, custom LASIK, IntraLASIK, and PRK. LASIK and other refractive procedures are extremely detail-sensitive, technologically complex forms of surgery. If you choose laser eye surgery, your procedure should be performed only by a highly trained and experienced refractive eye surgeon whom you have pre-screened and selected using specific criteria.
Originally used only in cataract surgery, intraocular lenses (IOLs) are being increasingly recommended as a form of vision correction for patients who are not good candidates for refractive surgery. While refractive eye surgeries work to correct vision by manipulating the cornea, IOLs are implanted in place of the eye’s natural lens. The latest innovation in medical lens correction procedures is the implantable contact lens (ICL). This device is similar to an IOL except it does not require the removal of the eye’s natural lens.
For more information on the surgical options that can reduce your dependency on glasses, schedule a patient consultation with an experienced eye surgeon in your area. These comprehensive information sessions are usually provided free of charge and are crucial in determining whether you are a good candidate for a specific procedure.
Schedule an Eye Appointment with an Eye Care Specialist

EYE EXAMS

The quality of your vision can easily deteriorate as a result of age or disease. Regular eye exams are the best means available for the early detection of eye disorders that, if not treated, can lead to vision problems and possibly even blindness. If it’s been more than a year or two since your last eye test, then today is the day you should schedule a complete eye examination. Read on for more information about why eye exams are important and what to expect during your visit to your local ophthalmologist.
Why Is It Important to Undergo Regular Eye Exams?
When diagnosed early on, many eye diseases can be cured or treated, helping to prevent permanent vision impairment. Unfortunately, many diseases of the eye have no noticeable symptoms in their earliest stages. While the early warning signs of a serious eye disorder may be invisible to you, they are often easily detectable through an eye test performed by a trained ophthalmologist.
Eye exams can also reveal the earliest clues to the presence of an overall body ailment. For example, one of the earliest signs of diabetes is the leaking of fragile blood vessels in the eye. High blood pressure and high cholesterol may also be detected by your eye doctor before the condition becomes apparent to your regular physician.
How Often Should I Schedule Eye Exams?
Most eye care experts recommend that people undergo a complete eye exam every one to three years, depending upon age, physical condition, and what risk factors are present. If you have already been prescribed eyeglasses or contact lenses, you should undergo a complete eye test annually. Along with screening for eye diseases, an exam will allow your eye doctor to check on the stability of your lens prescription and possibly take action if your eye condition is deteriorating at an abnormal rate.
A child’s first eye exam should normally be scheduled before he or she reaches six months of age. Children with a family history of eye disease or who have exhibited developmental delays should have an annual eye exam. We have a page devoted to child and teen vision concerns so you can learn more about eye care for children.
Adults diagnosed with diabetes, high blood pressure, or other diseases may need to be tested for vision problems more frequently. A physician can advise these patients as to how often eye testing should be performed. Adults over the age of 40 should have their eyes tested a minimum of every two years to allow for early detection of common age-related eye maladies, such as presbyopia, cataracts, and macular degeneration. We have a page devoted to adult vision concerns so you can learn more about eye care for adults.
What Kind of Eye Tests Will the Doctor Conduct?
Eye exams tend to begin with your doctor asking a series of questions about your medical history and eye health. The exam will then involve a series of tests, none of which will cause the patient pain or discomfort.
Visual Acuity Tests
Most people are familiar with the Snellen Chart, even if they do not know it by name. The chart is organized as a series of lines populated by random letters that decrease in size from the top of the chart to the bottom. Visual acuity tests for distance vision are commonly used in the eye screenings children receive in the school nurse’s office as well as in the test you probably had to undergo at the DMV to get your driver’s license. A modified version of this test can also be used to test your near vision. The Snellen Chart is a quick and easy way to detect refractive errors and can help determine the overall quality of your vision.
Eye Movement and Peripheral Vision Tests
During an eye exam, eye movement and peripheral vision are tested by moving an object, usually a small light, through the patient's field of vision. If initial peripheral vision testing results are ambiguous and your doctor has reason to think there may be a problem, a chart consisting of a series of concentric circles will be employed to better pinpoint possible blind spots in the edges of your vision. The loss of peripheral vision can be a sign of serious disorders in the eye or brain, so it is important that your eye doctor follow up on any suspected vision anomalies. The eye’s responsiveness to light is measured to ensure that your retina is exhibiting the proper level of photosensitivity.
Colorblindness Tests
Patterns composed of multicolored dots arranged in a pattern to form specific numbers and letters are used to test colorblindness. The test is designed in such as way as to prevent a colorblind person from being able to read the symbols in each pattern. Although color vision can sometimes be affected by the yellowing of the cornea with age, the most common forms of colorblindness are hereditary and present at birth.
In the vast majority of cases, colorblindness is not treatable, but depending upon the severity of the condition, a color blind person can learn to distinguish colors based on lightness and darkness rather than hue. Young people should be tested for colorblindness prior to obtaining their driving permit. A common disability among the severely colorblind is the inability to properly interpret traffic light signals.
Tonometry Tests
Tonometry tests are often performed while you are seated at a slit lamp. A slit lamp is a type of microscope with a light attached to it that is specially designed to give your eye doctor a magnified view of your anterior eye structures, such as the lens, cornea, and iris. An air puff tonometer may also be used. This instrument directs a puff of air at the eye in order to temporarily flatten the cornea. A cornea that does not respond to the air puff is indicative of high intraocular (inner eye) pressure. The air puff eye test is less precise than other methods, but it is also quicker, so it is often used to screen children.
Ophthalmoscopy
An ophthalmoscopy is also usually administered in eye exams. During this part of an eye exam, the eye is dilated using special eye drops. The retina, fundus (back of the eye), retinal vessels, and optic nerve head (optic disc) are then viewed with an ophthalmoscope, another type of microscope with an attached light.
Although these tests may seem time consuming when considered individually, a complete eye exam usually only takes about an hour. Your vision is precious. A single hour every one to two years is a small price to pay for maintaining the health of your eyes.
What Types of Conditions Can an Eye Exam Diagnose?
The eye functions like a complex machine, and there are many things that can go wrong with its individual processes. Here is a list of eye conditions that can be detected during the different phases of an eye test. You can click on the links for more information about each disorder.
Conditions Diagnosed During Visual Acuity Tests
Myopia
Astigmatism
Hyperopia
Presbyopia
Cataracts
Low Vision
Amblyopia (Lazy Eye)
Conditions Diagnosed During Eye Movement and Peripheral Vision Tests
Strabismus (Crossed Eyes)
Refractive Errors
Glaucoma
Conditions Diagnosed During Colorblindness Tests
Colorblindness
Conditions Diagnosed During Tonometry Tests
Glaucoma
Pink Eye (Conjunctivitis)
Blepharitis
Conditions Diagnosed During Ophthalmoscopy
Diabetic Retinopathy
Macular Degeneration
Retinal Detachment
Dry Eye Syndrome
Eye Allergies
Cataracts
Glaucoma

PRESBYOPIA

Presbyopia is a vision condition in which the crystalline lens of the eye begins to harden and lose flexibility, making it difficult to focus on objects up close. Presbyopia usually occurs around or after the age of 40, which is why it is sometimes referred to as age-related farsightedness.
Presbyopia Symptoms
Presbyopia is characterized by the inability to focus on objects that are closer than an arm’s distance away. If you suffer from presbyopia, words will appear blurry as you read, and you may find yourself needing more or brighter light in order to see clearly at night. Individuals with presbyopia begin to experience difficulty reading newspapers, books, menus, and other objects at close distances, even if they have had perfect vision their whole lives. Many patients also experience pain, fatigue, and headaches as a result of the extra strain on their eyes.
Causes of Presbyopia
Age-related farsightedness usually results from a loss of flexibility in the eye’s crystalline lens, which tends to harden over time. Presbyopia is caused by a gradual loss of the lens’ ability to flatten and thicken, which it must do to focus on close objects. Although presbyopia seems to come on suddenly, it actually takes place over a period of several years. Because it is a natural part of the eye’s aging process, it cannot be prevented and may worsen over time.
Hyperopia vs. Presbyopia
Although the symptoms of hyperopia and presbyopia are similar, their causes are actually quite different. Hyperopia is a refractive error that causes up-close objects to appear blurry. With hyperopia, the eye is too short from front to back, causing light to be focused behind the eye rather than on the retina. Hyperopia is usually present from birth, whereas presbyopia comes on later in life.
Presbyopia Diagnosis
Presbyopia can be diagnosed through a comprehensive eye exam, during which your ophthalmologist will conduct a number of tests to determine your degree of presbyopia and any other problems with your eyes. One of the things he or she will have you do is read a series of words from a distance that is typically comfortable. You will then try out several corrective prescriptions to determine which one will best correct your farsightedness. For more information about eyeglasses and other corrective options, see the presbyopia treatment page.
Degrees of Presbyopia – Moderate to Severe
The degree of age-related farsightedness you experience can vary greatly, from mild to severe. People with mild presbyopia sometimes choose not to wear corrective lenses, but those with moderate to severe presbyopia will need to seek treatment in order to read and carry out other day-to-day functions.
Presbyopia is part of the natural aging process and cannot be prevented. However, people who spend a lot of time in front of a computer or who do close visual work may develop more severe symptoms earlier in life. If you engage in up-close work, you can help avoid developing premature presbyopia by taking frequent breaks, during which time you should focus your eyes on distant objects.

ASTIGMATISM

Astigmatism is a common refractive error that results from an imperfection in the eye’s curvature. In normal eyes, the cornea (the front part of the eye’s surface) and the lens are smooth and evenly shaped in all directions. With astigmatism, the cornea or lens is irregularly shaped in some areas, causing blurred vision. Astigmatism is not an eye disease; it is simply a variation in the way the eye is shaped. A person can experience moderate to severe astigmatism depending on how many corneal or lens disturbances are present. Read on to learn more about the causes of astigmatism, its symptoms, and diagnosis.
Astigmatism Symptoms
The most common symptom of astigmatism is blurred vision at any distance. People with astigmatism often experience distortions of vertical, horizontal, or diagonal lines, as well as frequent headaches and fatigue, squinting, eye discomfort, and irritation. These symptoms are not exclusive to astigmatism and will vary depending on whether the patient has mild, moderate, or severe astigmatism. If you experience any of these symptoms, you should contact a qualified ophthalmologist for a comprehensive eye examination.
Causes of Astigmatism
In the human eye, the cornea focuses images by refracting incoming light onto the retina (back of the eye). In the ideally-shaped eye, the cornea has a smooth, even curvature and is shaped like a round ball. With astigmatism, the cornea is shaped more like an oval, or football, causing light to scatter as it passes through. The result is a blurred image on the retina, making it difficult for people with astigmatism to see clearly at any distance.
Contrary to common belief, reading in poor light, squinting, or sitting too close to the television are not causes of astigmatism. Astigmatism is usually present from birth and can either stay the same or worsen over time. Eye injury, disease, or surgery can also be causes of astigmatism.
Astigmatism Diagnosis
Astigmatism is usually diagnosed during routine eye exams, wherein your ophthalmologist will check your eye’s refraction (ability to properly focus light rays on the retina) and visual acuity using a standard eye chart. The eye’s refraction can be measured in a number of ways; some doctors will simply ask a series of questions about your current vision and conduct a visual acuity test, while others will use a keratometer or keratoscope to assess the curvature of your cornea and determine the presence of moderate or severe astigmatism.
Moderate to Severe Astigmatism
Many experts believe that all people are born with a degree of astigmatism that may worsen or stay the same throughout their lifetime. For most people, the degree of astigmatism experienced is so mild that it does not require corrective lenses. However, for those with moderate to severe astigmatism, eyeglasses or contact lenses must be worn unless their vision is corrected with refractive surgery.
Degree of Refractive Error
The term refractive error refers to the degree to which images received through the eye's cornea and lens are not focused on the retina. In other words, it is the degree of “blurriness” that a person experiences when trying to focus on images at varying distances. The numbers on a person’s eyeglass or contact prescription reflect this measurement. With astigmatism, the degree of refractive error is noted under “C,” or “cylinder,” which measures the eye’s irregular curvature. A person’s prescription can vary greatly depending on whether he or she has moderate or severe astigmatism, and it must remain stable before LASIK or other refractive surgery can be performed.

HYPEROPIA

Hyperopia is a term used to describe the condition of being farsighted. The causes of hyperopia are typically genetic and involve an eye that is too short or a cornea that is too flat, so that images focus at a point behind the retina. People with hyperopia can usually see distant objects well, but have trouble focusing on nearby objects.
Hyperopia Symptoms
People who have hyperopia may have trouble seeing objects that are close up. In some cases, they may not recognize that they have a vision problem, but will notice that their eyes become tired or sore during such activities as reading or writing. This is because, for mildly farsighted people, the lens of the eye has a tendency to accommodate for the refractive error. Over time, however, the lens’ ability to adjust diminishes, and people with hyperopia will need treatment to correct their vision.
Causes of Hyperopia
Like myopia, hyperopia is a genetic trait; however, instead of the eye being too long (as in myopia), it is too short, causing images to focus at a point beyond the retina. Though it is not uncommon for hyperopia to be associated with aging, getting older does not cause people to become farsighted. Rather, the aging process hinders the eye’s focusing ability, which can sometimes make pre-existing hyperopia more evident. Learn more about age-related farsightedness (presbyopia).
Hyperopia Diagnosis
If the causes of hyperopia are present in a child’s family, the child has a good chance of inheriting the condition. However, a typical grade-school screening or visual acuity test will usually not be adequate to detect hyperopia. An ophthalmologist, through a comprehensive eye exam, will be able to not only detect problems, but can determine the degree and ideal treatments for those problems as well. Young people with mild hyperopia may not need corrective lenses or any type of treatment while people who are older or are severely farsighted will have a variety of treatment options available to them.
Moderate to Severe Hyperopia
People with hyperopia are considered farsighted because they can generally see objects in the distance more clearly than objects up close. People who are moderately or severely farsighted, however, may have trouble seeing objects at any distance. If the refractive error is bad enough, the lens will not be able to accommodate for it and treatment will become necessary. Children who are severely farsighted have a higher risk for strabismus (crossed eyes) or amblyopia (lazy eye), so they should be examined and treated accordingly.
Degree of Farsighted Vision
Just like myopia, the degree of hyperopia is measured in diopters, which are units of measurement that describe lens strength. Myopic prescriptions have negative numbers and measurements of hyperopia are made with positive numbers. A person with a prescription of +2.0 diopters or less has mild hyperopia. A degree of hyperopia of between +2.0 and +4.0 diopters considered moderate. Someone who is severely farsighted will need a prescription of +4.0 diopters or higher.

MYOPIA

A person with myopia is said to be nearsighted, because they can see objects that are up close, but have trouble seeing images or objects that are far away. Although myopia is generally a mild and manageable condition, severe myopia can trigger much more serious eye problems and can potentially lead to blindness. Learn more about myopia by reading the sections below and visit our myopia treatments page for more information about how the condition can be treated.
Myopia Symptoms
Myopia is a type of refractive error that usually presents itself in children of about eight to twelve years old. Signs that a child may be nearsighted include squinting, difficulty seeing objects at a distance, and holding books or other objects very close to the face. Occasionally, a person with myopia may have headaches or eyestrain from the effort of trying to focus.
Causes of Myopia
Although theories abound as to what behaviors may trigger or worsen myopia, it is generally accepted within the medical community that nearsightedness is an inherited trait. Nearsighted people have eyes that are elongated or corneas that are more steeply curved than those of the average person, causing incoming light to focus at a point in front of the retina, rather than on it. This type of refractive error is most commonly found in those who have a direct relative with the same condition.
Myopia Diagnosis
Myopia can be easily diagnosed during a routine eye exam. Usually, a visual acuity test combined with a refraction assessment can not only identify nearsightedness, but can also determine the degree of myopia. The visual acuity test involves reading a special chart from a specific distance. Based on how much of the chart the patient can read, the doctor is able to determine how clearly the patient can see. During a refraction assessment, the patient is asked to look through a device called a Phoropter while the eye doctor changes lenses and asks the patient questions. This allows the doctor to determine what prescription will most effectively correct the patient’s vision.
Moderate to Severe Myopia
People who have moderate or severe myopia may only be able to see objects that are within a few inches of their faces without the aid of corrective lenses. Degenerative myopia, a rare condition in which the eye continues to elongate far beyond a normal range, can lead to a variety of serious complications. These include stretching and thinning of the eye’s outer shell, or sclera, retinal detachment, macular degeneration, increased likelihood of cataracts, and even glaucoma.
Degree of Nearsighted Vision
A diopter is a unit used to measure lens strength. It can also be used to describe the degree of myopia a person has. A person with mild myopia will have a prescription of -3.0 diopters or less. Someone with a degree of myopia of between -3.0 and -6.0 diopters is said to be moderately nearsighted. Measurements of -6.0 diopters and higher are considered severe. The degree of a person’s myopia will affect their candidacy for procedures such as LASIK and PRK.

REFRACTIVE ERRORS

The three most common refractive errors are myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. These imperfections can be surgically corrected with LASIK, custom LASIK, PRK, and other vision correction procedures. Presbyopia, a refractive disorder that comes with age, can be treated with LASIK monovision, the placement of implantable lenses, and conductive keratoplasty.
What is a Refractive Error?
Refractive errors refer to a disorder in which the eye is irregularly shaped, causing light to focus on the wrong area of the retina. Refractive errors result in varying degrees of blurry vision, but can be treated with eyeglasses, contact lenses, and refractive surgery. The most common types of refractive errors are myopia, hyperopia, and astigmatism. Learn more about these refractive errors, as well as presbyopia, an age-related condition.
Myopia (Nearsightedness)
Myopia, or nearsightedness, occurs due to an irregularly shaped cornea. This causes light rays to focus in front of the retina, rather than directly on the retina. Nearsighted patients experience clear vision up close, but distant objects will be fuzzy. Learn more about myopia, as well as the treatments available for nearsighted individuals.
Hyperopia (Farsightedness)
Hyperopia, or farsightedness, occurs due to an irregularly shaped cornea that causes light to focus behind the retina, rather than directly on the retina. Farsighted individuals have difficulty seeing objects up close, but see distant objects clearly. Learn more about hyperopia and the treatment options available for farsighted patients.
Astigmatism
The most common of all eye disorders, astigmatism occurs when the eye is shaped more like a football than a basketball. This odd shape causes the light to focus on two points of the retina, rather than one.
Astigmatism is often accompanied by either nearsightedness or farsightedness. If this is the case, both refractive errors can be treated simultaneously. Learn more about astigmatism and the types of astigmatism treatments currently in use.
Presbyopia
Presbyopia is an eye condition that comes with age, hindering the up-close focusing ability of the eye. It generally starts affecting patients between the ages of forty and fifty. Presbyopia is currently being treated in a number of ways. Learn more about presbyopia and the latest presbyopia treatment options.

THE OPTIC NERVE

The optic nerve (also known as cranial nerve II) is a continuation of the axons of the ganglion cells in the retina. There are approximately 1.1 million nerve cells in each optic nerve. The optic nerve, which acts like a cable connecting the eye with the brain, actually is more like brain tissue than it is nerve tissue.
visual pathway
As the optic nerve leaves the back of the eye, it travels to the optic chiasm, located just below and in front of the pituitary gland (which is why a tumor on the pituitary gland, pressing on the optic chiasm, can cause vision problems). In the optic chiasm, the optic nerve fibers emanating from the nasal half of each retina cross over to the other side; but the nerve fibers originating in the temporal retina do not cross over.
From there, the nerve fibers become the optic tract, passing through the thalamus and turning into the optic radiation until they reach the visual cortex in the occipital lobe at the back of the brain. This is where the visual center of the brain is located.
The visual cortex ultimately interprets the electrical signals produced by light stimulation of the retina, via the optic nerve, as visual images. A representation of parasympathetic pathways in the pupillary light reflex can be seen here: parasympathetic response.
blind spot
The beginning of the optic nerve in the retina is called the optic nerve head or optic disc. Since there are no photoreceptors (cones and rods) in the optic nerve head, this area of the retina cannot respond to light stimulation. As a result, it is known as the “blind spot,” and everybody has one in each eye.
The reason we normally do not notice our blind spots is because, when both eyes are open, the blind spot of one eye corresponds to retina that is seeing properly in the other eye. Here is a way for you to see just how absolutely blind your blind spot is. Below, you will observe a dot and a plus.


Follow these viewing instructions:
Sit about arm’s length away from your computer monitor/screen.
Completely cover your left eye (without closing or pressing on it), using your hand or other flat object.
With your right eye, stare directly at the above. In your periphery, you will notice the to the right.
Slowly move closer to the screen, continuing to stare at the .
At about 16-18 inches from the screen, the should disappear completely, because it has been imaged onto the blind spot of your right eye. (Resist the temptation to move your right eye while the is gone, or else it will reappear. Keep staring at the .)
As you continue to look at the , keep moving forward a few more inches, and the will come back into view.
There will be an interval where you will be able to move a few inches backward and forward, and the will be gone. This will demonstrate to you the extent of your blind spot.
You can try the same thing again, except this time with your right eye covered stare at the with your left eye, move in closer, and the will disappear.
If you really want to be amazed at the total sightlessness of your blind spot, do a similar test outside at night when there is a full moon. Cover your left eye, looking at the full moon with your right eye. Gradually move your right eye to the left (and maybe slightly up or down). Before long, all you will be able to see is the large halo around the full moon; the entire moon itself will seem to have disappeared.
Like any other ocular structure, certain pathologies can have an adverse affect on the optic disc and optic nerve. Although there are too many to list completely, a few will be included here.
optic atrophy
“Optic atrophy” of the optic disc (visible to an eye doctor looking inside the eye) is the result of degeneration of the nerve fibers of the optic nerve and optic tract. It can be congenital (usually hereditary) or acquired.
If acquired, it can be due to vascular disturbances (occlusions of the central retinal vein or artery or arteriosclerotic changes within the optic nerve itself), may be secondary to degenerative retinal disease (e.g., optic neuritis or papilledema), may be a result of pressure against the optic nerve, or may be related to metabolic diseases (e.g., diabetes), trauma, glaucoma, or toxicity (to alcohol, tobacco, or other poisons).
Loss of vision is the only symptom. A pale optic disc and loss of pupillary reaction are usually proportional to the visual loss. Degeneration and atrophy of optic nerve fibers is irreversible, although in some cases, intravenous steroid injections have been seen to slow down the process.
optic neuritis
“Optic neuritis” is an inflammation of the optic nerve. It may affect the part of the nerve and disc within the eyeball (papillitis) or the portion behind the eyeball (retrobulbar optic neuritis, causing pain with eye movement). It also includes degeneration or demyelinization of the optic nerve. There will be no visible changes in the optic nerve head (disc) unless some optic atrophy has occurred.
This condition can be caused by any of the following:
demyelinating diseases (e.g., multiple sclerosis, postinfectious encephalomyelitis);
systemic infections (viral or bacterial);
nutritional and metabolic diseases (e.g., diabetes, pernicious anemia, hyperthyroidism);
Leber’s Hereditary Optic Neuropathy (a rare form of inherited optic neuropathy which mainly affects young men, causing them to lose central vision);
secondary complications of inflammatory diseases (e.g., sinusitis, meningitis, tuberculosis, syphilis, chorioretinitis, orbital inflammation);
toxic reactions (to tobacco, methanol, quinine, arsenic, salicylates, lead); and
trauma.
The condition is unilateral rather than bilateral. If the nerve head is involved, it is slightly elevated, and pupillary response in that eye is sluggish. There usually is a marked but temporary decrease in vision for several days or weeks, and there is pain in the eye when it is moved. Single episodes generally do not result in optic atrophy nor in permanent vision loss; however, multiple episodes can result in both.
papilledema
“Papilledema” is edema or swelling of the optic disc (papilla), most commonly due to an increase in intracranial pressure (often from a tumor), malignant hypertension, or thrombosis of the central retinal vein. The condition usually is bilateral, the nerve head is very elevated and swollen, and pupil response typically is normal.
Vision is not affected initially (although there is an enlargement of the blind spot), and there is no pain upon eye movement. Secondary optic atrophy and permanent vision loss can occur if the primary cause of the papilledema is left untreated.
ischemic optic neuropathy
“Ischemic optic neuropathy” is a severely blinding disease resulting from loss of the arterial blood supply to the optic nerve (usually in one eye), as a result of occlusive disorders of the nutrient arteries. Optic neuropathy is divided into anterior, which causes a pale edema of the optic disc, and posterior, in which the optic disc is not swollen and the abnormality occurs between the eyeball and the optic chiasm.
Ischemic anterior optic neuropathy usually causes a loss of vision that may be sudden or occur over several days. Ischemic posterior optic neuropathy is uncommon, and the diagnosis depends largely upon exclusion of other causes, chiefly stroke and brain tumor.
glaucoma
“Glaucoma” is an insidious disease which damages the optic nerve, typically because the “intraocular pressure” (IOP) is higher than the retinal ganglion cells can tolerate. This eventually results in the death of the ganglion cells and their axons, which comprise the optic nerve. Thus, less visual impulses are able to reach the brain.
In advanced glaucoma, the visual field in the peripheral retina is decreased or lost, leaving vision in the central retina (macular area) intact. This results in “tunnel vision.” Elevated eye pressure occurs when too much aqueous fluid enters the eye and not enough of the aqueous fluid is leaving the eye. Eye pressure can be measured by performing a “tonometry” test.
Normally, fluid enters the eye by seeping out of the blood vessels in the ciliary body. This fluid eventually makes its way past the crystalline lens, through the pupil (the central opening in the iris), and into the irido-corneal angle, the anatomical angle formed where the iris and the cornea come together. Then the fluid passes through the trabecular meshwork in the angle and leaves the eye, via the canal of Schlemm.
If the rate of aqueous fluid is entering the eye is too great, or if the trabecular meshwork “drain” gets clogged (for instance, with debris or cells) so that the fluid is not leaving the eye quickly enough, the pressure builds up in what is known as “open angle glaucoma.” It is more common with increasing age.
Open angle glaucoma, which tends to be a chronic and painless condition, also can be caused when the posterior portion of the iris, surrounding the pupil, somehow adheres to the anterior surface of the lens (creating a “pupillary block”). This can prevent intraocular fluid from passing through the pupil into the anterior chamber.
On the other hand, if the angle between and iris and the cornea is too narrow, or is even closed, then the fluid backs up because it cannot flow out of the eye properly. This causes an increased intraocular pressure in what is known as “closed angle glaucoma.” Typically, there is an acute (sudden), painful onset. It can be accompanied by the appearance of rainbow-colored rings around white lights.
An internal pressure more than that which the eye can tolerate can deform the lamina cribrosa, the small cartilaginous section of the sclera at the back of the eye through which the optic nerve passes. A deformed lamina cribrosa seems to “pinch” nerve fibers passing though it, eventually causing axon death. Untreated glaucoma eventually leads to optic atrophy and blindness.
Eye pressure is measured by using a “tonometer” (with the test being called “tonometry”), and the standard tonometer generally is considered to be the “Goldmann tonometer.” The normal range of intraocular pressure (IOP) is 10 mm Hg to 21 mm Hg, with an average of about 16 mm Hg. Typically, eyes with intraocular pressure measurements of 21 mm Hg or higher, using a Goldmann tonometer, are considered to be “ocular hypertensive” and are suspect for glaucoma.
However, although glaucoma typically is associated with elevated IOP, the amount of pressure which will cause glaucoma varies from eye to eye and person to person. Many people with glaucoma actually have IOP’s in the normal range (“low tension” glaucoma), possibly indicating that their lamina cribrosas are too weak to withstand even normal amounts of pressure. Conversely, many people with IOP’s which would be considered high have no evidence of glaucomatous damage.
Glaucomatous changes in the optic disk (optic nerve head) usually can be detected over time. If the optic cup within the optic disk increases in size over a period of months or years, if notching is observed anywhere around the nerve head rim, and/or if an asymmetry is observed between the optic cups of the two eyes, then that person may be considered to be a “glaucoma suspect.” In glaucoma, optic nerve rim atrophy and/or notching, with a corresponding visual field decrease, usually will occur in this order:
Optic Nerve Quadrant
Visual Field Loss
1. Inferior Quadrant
Superior Field
2. Superior Quadrant
Inferior Field
3. Temporal Quadrant
Nasal Field
4. Nasal Quadrant
Temporal Field
Visual field loss, caused by optic nerve damage, is measured by using a “visual field analyzer” or “perimeter,” especially by measuring and comparing changes over time. The procedure is known as “perimetry.” Most field loss due to glaucoma usually is not even measurable until 25% to 40% of the optic nerve’s axons have been destroyed.
Studies seem to show that the first fibers to die are the larger fibers, which primarily carry form and motion information, rather than the smaller fibers, which primarily detect light. Therefore, pattern discrimination perimetry (PDP), which requires detection of both form and motion, may be a better test for early glaucoma than conventional perimetry, which requires detection of spots of light.
In PDP, various locations of the retina are stimulated with a checkerboard pattern on a background of randomly moving dots. The more random the dot movements, the more difficult it is to continue to perceive the checkerboard pattern. Even a normal eye eventually will not be able to see the checkerboard when the dot movement is random enough.
The more advanced the stage of glaucomatous nerve damage, the less “noisy” the dots need to be for the checkerboard pattern to be indistinguishable from the background of moving dots. In effect, the PDP seems to be more sensitive than a standard perimeter in detecting early glaucomatous visual field losses.
Typically, the elevated pressure in open angle glaucoma can be controlled using glaucoma medications, which either decrease the production of aqueous fluid or else increase its outflow from the eye. However, closed angle glaucoma often requires surgical intervention to be controlled.