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.