Glaukoma Menyebabkan Kebutaan

Penulis: Oleh: dr Tiur Marlina Siregar PNS Pustu Kemang Masam,
Muntok, Bangka Barat

Glaukoma adalah istilah yang digunakan untuk kelompok penyakit mata
yang ditandai dengan peningkatan tekanan di dalam bola mata atau
tekanan intra-okuler (TIO) sehingga menyebabkan rusaknya saraf optik
yang membentuk bagian-bagian retina di belakang bola mata. Saraf
optik menyambung jaringan-jaringan penerima cahaya (retina) dengan
bagian dari otak yang memproses informasi penglihatan.

Glaukoma adalah bagian penyakit mata yang menyebabkan proses
hilangnya penglihatan, tetapi proses ini dapat dicegah dengan obat-
obatan, terapi laser dan pembedahan. Hilangnya penghlihatan pada
kasus glaukoma tidak dapat disembuhkan kembali, maka sangat penting
untuk mencegah terjadinya kerusakan pada organ mata sedini mungkin,
apalagi glaukoma seringkali timbul tanpa gejala sampai pada tahap
akhir, kecuali glaukoma jenis akut (tekanan bola mata tiba-tiba
meninggi sehingga mata terasa sakit dan pegal).

Pada fase lanjut glaukoma memiliki gejala-gejala seperti penglihatan
kabur, sakit kepala, melihat pelangi bila melihat cahaya terang serta
hilangnya penglihatan sisi samping.

Pada fisiologi mata yang normal, cairan di dalam mata dihasilkan oleh
badan siliar di bilik mata di belakang, berdifusi melalui pupil ke
dalam bilik mata depan. Cairan ini akan dialirkan ke dalam sistem
pembuluh darah melaui anyaman trabekulum schlemm yang terdapat di
sudut bilik mata depan.

Glaukoma didefinisikan sebagai peningkatan TIO secara mendadak dan
sangat tinggi akibat hambatan di anyaman trabekulum. Keadaan itu
merupakan suatu kedaruratan mata yang termasuk true emergency.

Secara khusus gejala klinis glaukoma dibagi menjadi glaukoma yang
akut dan kronis. Berdasarkan anatomi sudut bilik mata depan, glaukoma
dibedakan atas glukoma sudut tertutup dan glukoma sudut terbuka,
sedangkan berdasarkan penyebabnya, glukoma dibedakan menjadi glaukoma
primer dan sekunder.

Bahaya glaukoma akut harus diwaspadai termasuk oleh dokter umum,
karena menyebabkan kebutaan yang cepat pada kedua mata. Pasien datang
ke bagian unit darurat dengan keluhan utama nyeri di sekitar mata dan
menurunnya ketajaman penglihatan, dapat disertai sakit kepala, muntah
dan sakit perut sehingga dapat didiagnosis terjadi gangguan
pencernaan atau gastritis.

Risiko terjadinya glaukoma bertambah tinggi dengan bertambahnya usia.
Terdapat 2% dari populasi usia 40 tahun terkena glaukoma. Angka ini
dapat bertambah bila usia semakin bertambah pula. Begitunya riwayat
anggota keluarga yang terkena glaukoma sebelumnya, pemakaian obat-
obat steroid dalam jangka waktu lama, riwayat trauma pada mata,
penyakit-penyakit sistemik seperti penyakit darah tinggi, penyakit
gula.

Pemeriksaan mata lebih lanjut diperlukan guna memastikan diagnosis
glaukoma. Pemeriksaan mata tersebut meliputi tajam penglihatan,
pemeriksaan mata luar, pupil pergerakan bola mata, pemeriksaan lapang
pandang dengan humprey visual field test, pemeriksaan fundus, dan
pemeriksaan tekanan dalam bola mata dengan Non Contac Tonometry (NCT).

Glaukoma menyebabkan menurunnya penglihatan hingga 1/300. Akibatnya,
penderita hanya melihat gerakan tangan saja (hand movement). Tekanan
bola mata yang meningkat tinggi umumnya melebihi 50 mmHg.
Meningkatnya tekanan bola mata itu dapat menyebabkan kerusakan dan
iskemia saraf mata serta oklusi pembuluh darah retina. Pemeriksaan
lain yang dapat dilakukan adalah dengan melakukan gonioskopi dan
funduskopi dengan melihat keadaan bilik dan saraf mata akibat
peningkatan tekanan.

Untuk menurunkan tekanan bola mata, penderita harus segera dirujuk ke
rumah sakit. Posisi yang dianjurkan pada penderita glaukoma adalah
terlentang dan tidak boleh diberikan penutup mata. Di ruang unit
darurat terapi glaukoma akut diusahakan menurunkan tekanan bola mata,
menekan inflamasi, dan mengembalikan sudut bilik mata depan yang
menutup. Seharusnya pengobatan glaukoma dilakukan oleh spesialis
mata, namun dokter umum dapat melakukan terapi sementara bila tidak
ada spesialis mata sebelum akhirya melakukan konsul spesialis mata.

Terapi inisial terdiri dari asetazolamid, tetes mata beta bloker dan
kortikosteroid topical. Azetazolamid diberikan dengan dosis 500 mg
intravena, diikuti pemberian oral 500 mg atau 1000 mg oral.

Beta bloker topical yang digunakan adalah timolol 0,5 % atau
betaxolol 0,5 % dengan dosis 2 kali sehari. Beta bloker dan
asetazolamid menurunkan produksi humor akuos dan membuka sudut bilik
mata depan. Obat alpha agonist topikal, misalnya brimonidin dapat
ditambahkan guna menurunkan tekanan bola mata lebih lanjut.
Kortikosteroid topikal, dengan aau tanpa antibiotik, dapat mengurangi
reaksi inflamasi pada penderita glaukoma dan mengurangi saraf optik.
Terapi simptomatik dapat diberikan untuk mengatasi gejala, misalnya
analgesik untuk mengurangi rasa sakit pada mata, serta anti muntah
untuk mengatasi mual dan muntah.

Setelah terapi inisial, harus dilakukan penilaian ulang terhadap
tekanan bola mata dan pertimbangan untuk melakukan terapi lanjut
seperti pemberian agen hiperosmotik oral. Bila no belum turun,
diberikan larutan gliserin 50% oral dengan dosis 4 kali 100 - 150 ml
sehari, yang diberikan dengan ditambahkan jus buah dan batu es untuk
mengurangi efek mual pada penderita saat minum larutan tersebut. Obat
lain adalah isosorbid (dapat diberikan pada penderita diabetes
militus) dan manitol intravena 20% yang diberikan dalam jumlah
400-500 ml.

Obat hiperosmotik tidak dapat diberikan pada pasien dengan penyakit
kardiovaskuler dan penyakit ginjal. lridotomi laser merupakan terapi
definitive glaukoma sudut tertutup akut, yang dilakukan 24-48 jam
setelah tekanan bola mata terkontrol. Saat ini iridotomi laser
merupakan pilihan utama, namun jika fasilitas laser belum tersedia
dapat dilakukan iridektomi dengan pembedahan.

Penatalaksanaan glaukoma sekunder akut tergantung pada penyebabnya.
Bila disebabkan katarak hipermatur, dilakukan bedah katarak. Bila
disebabkan uveitis, dilakukan terapi terhadap uveitis, selain
menurunkan tekanan bola mata.

Semlia terapi ini pada prinsipnya adalah bertujuan untuk menurunkan
tekanan bola mata. Untuk pengobatan/terapi yang cocok disarankan
sesuai kondisi penyakit glaukoma dan kondisi keadaan umum pasien.
Sebagian obat-obatan glaukoma dapat berinteraksi ke dalam tubuh,
sehingga obat-obatan tertentu merupakan kontraindikasi.

Penyakit-penyakit yang mungkin kontraindikasi dengan penyakit
glaukoma yaitu: penyakit asma, penyakit gangguan irama jantung,
alergi terhadap sulfa. Keadaan umum lain yan merupakan kontraindikasi
ialah kehamilan. Obat-obatan glaukoma sebagian besar disekresi ke air
susu dan dapat menembus plasenta. Jadi penderita glaukoma yang sedang
hamil disarankan melakukan prosedur laser atau pembedahan untuk
pengobatan glaukomanya.

Oleh karena itu sangat penting bagi pasien untuk memberitahukan
penyakit-penyakit yang diderita lama sehingga dokter dapat memilih
terapi dan pengobatan yang sesuai.

KESEHATAN MATA

Mitos: Konsumsi wortel setiap hari akan membuat mata sehat, pandangan jernih dan mencegah rabun jauh.

Fakta: Wortel mengandung karoten yang bermanfaat untuk kesehatan mata. Tapi sumber karoten tidak hanya wortel. Buah lain seperti pepaya, mangga juga mengandung karoten yang tinggi, bahkan buah merah dari Papua yang sedang tren saat ini telah diteliti mengandung karoten yang jauh lebih tinggi dari buah-buah lainnya. Jadi meski wortel bermanfaat untuk kesehatan mata, tidak perlu mengonsumsinya setiap hari. Sumber karoten bisa diselang-seling dengan buah-buah lainnya dalam jumlah secukupnya.

Orang pun menganggap sayuran yang mengandung vitamin A ini berperan besar dalam fungsi penglihatan ma-nusia. Tapi sebenarnya vitamin A yang ada dalam wortel lebih banyak berperan pada me-tabolisme sel-sel saraf yang ada di retina. Jadi banyak makan wortel pun tak dapat mecegah bertambahnya/mengurangi jumlah minus/plus/ silinder lensa kacamata anak. Mak-sudnya, kalau pangkal kesalahan terjadi pada sistem optik tentu vitamin A tidak bisa memperbaiki keadaan tersebut. Sama dengan kamera yang lensanya sudah tidak fokus. Film dengan merek apapun yang dipakai tetap akan menghasilkan gambar buram

Mitos: Membaca sambil tiduran menyebabkan rabun jauh.

Fakta: Mitos ini tidak benar. Seseorang yang sudah punya kecenderungan rabun jauh, misalnya dalam keluarga hampir semua menderita rabun jauh, meski tidak pernah membaca sambil tiduran, tetap saja potensial terkena rabun jauh. Yang menjadi masalah dalam aktivitas ini adalah apabila jarak baca terlalu dekat. Seperti diketahui membaca sambil tidur biasanya membuat jarak buku dengan mata makin lama makin dekat sehingga mata dipaksa untuk terus fokus dalam jarak yang tidak ideal. Tidak hanya sambil tiduran, membaca sambil duduk atau berdiri sekalipun kalau jarak-nya kurang dari 12 inci (sekitar 30 cm) membuat mata cepat lelah sehingga dalam jangka panjang bisa menyebabkan gangguan rabun jauh.

Mitos: Membaca dengan cahaya remang-remang menyebabkan rabun jauh.

Fakta: Membaca dalam ruang yang penerangannya kurang membuat mata cepat lelah. Seperti laiknya melihat dalam gelap, mata harus berakomodasi maksimal supaya objek dapat terlihat. Saat membaca sebaiknya penerangan dalam ruangan tersebut cukup, lebih baik lagi kalau cahaya datang dari arah belakang anak. Tak hanya remang-remang, cahaya yang berlebihan pun sama tak layaknya untuk kesehatan mata.

Mitos: Melihat laut/pemandangan hijau dapat menyembuhkan rabun jauh.

Fakta: Seperti otot-otot lainnya, otot mata pun butuh relaksasi. Sebagai gambaran, seseorang yang duduk terlalu lama, pinggangnya akan terasa pegal-pegal. Demikian halnya dengan mata. Kalau mata digunakan untuk melihat satu fokus yang sama dalam waktu lama, misalnya membaca buku yang tebal akan terasa sangat lelah. Untuk itu disarankan melihat titik terjauh sebagai relaksasi otot mata. Tidak harus melihat laut/pemandangan hijau, yang penting melihat titik terjauh. Dan yang harus diingat kegiatan ini bukan untuk menyembuhkan rabun jauh melainkan sekadar sebagai relaksasi otot mata.

Mitos: Kacamata harus dipakai terus-menerus supaya minus mata tidak bertambah.

Fakta: Mitos ini sama sekali tidak benar. Seorang dengan gangguan rabun jauh akan kesulitan melihat tanpa kacamata. Itulah sebabnya kacamata harus dipakai. Tapi tentu saja tidak di setiap kesempatan kacamata harus dipakai terus. Bertambahnya minus disebabkan jarak retina ke lensa makin panjang seiring bertambahnya usia dan bukan karena dipakai/tidaknya kacamata.

Ada juga anggapan kacamata jangan terus-terusan dipakai karena malah akan menambah minus. Ini juga tak masuk logika. Sama dengan anggapan kalau kacamata harus selalu dipakai agar kelainan refraksi tak tambah parah. Perkembangan ukuran bola mata sama seperti perkembangan tubuh manusia. Ukuran bola mata bayi akan lebih kecil ketimbang ukuran bola mata orang dewasa. Hal ini berarti dari masa bayi hingga masa dewasa sebetulnya terjadi perkembangan pada ukuran/dimensi bola mata. Pada 2 tahun pertama yang sangat berkembang adalah sistem optik di bagian depan mata (segmen depan), yaitu sebesar 60 %. Setelah usia 2 tahun segmen depan masih berkembang tapi sudah tidak begitu pesat.

Segmen belakang akan tumbuh pesat saat usia anak berkisar antara 4 sampai 15 tahun yang kemudian menjadi lambat perkembangannya dan berhenti di sekitar usia 18 tahun. Artinya bagian belakang bola mata di mana retina berada makin lama makin panjang sesuai dengan pertambahan usia. Jadi kalau pada usia 6 tahun, mata anak sudah mencapai minus dua, itu karena jarak retina ke lensa makin panjang sehingga minusnya pun akan bertambah besar. Dengan kata lain, penambahan minus pada usia pertumbuhan bisa dikatakan alamiah.

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.