The word “astigmatism” is used so much in the ophthalmic world that most people have talked about it when discussing their eye health with their doctor.
“Astigmatism” comes from the Greek “a” – meaning “without” – and “stigma” – meaning “a point.” In technical ocular terms, astigmatism means that instead of there being one point of focus in the eye, there are two. In other words, light merges not on to a singular point, but on two different points.
This is experienced in the real world by blurred, hazy vision, and can sometimes lead to eye strain or headaches if not corrected with either glasses or contact lenses.
Astigmatism is not a disease. In fact, more than 90% of people have some degree of astigmatism.
Astigmatism occurs when the cornea, the clear front surface of the eye like a watch crystal, is not perfectly round. The real-world example we often use to explain astigmatism is the difference between a basketball and a football.
If you cut a basketball in half you get a nice round half of a sphere. That is the shape of a cornea without astigmatism.
If you cut a football in half lengthwise you are left with a curved surface that is not perfectly round. It has a steeper curvature on one side and a flatter curve on the other side. This is an exaggerated example of what a cornea with astigmatism looks like.
The degree of astigmatism and the angle at which it occurs is very different from one person to the next. Therefore, two eyeglass prescriptions are rarely the same because there are an infinite number of shapes the eye can take.
Most astigmatism is “regular astigmatism,” where the two different curvatures to the eye lie 90 degrees apart from one another. Some eye diseases or surgeries of the eye can induce “irregular astigmatism,” where the curvatures are in several different places on the eye’s surface, and often the curvatures are vastly different, leading to a high amount of astigmatism.
Regular astigmatism is treated with glasses, contact lenses, or refractive surgery (PRK or Lasik). Irregular astigmatism, such as that caused by the eye disease keratoconus, usually cannot be treated with these conventional methods. In these circumstances, special contact lenses are needed to treat the condition.
The next time you hear that either you or a loved one has astigmatism, fear not.
It is easily corrected, and although astigmatism can cause your vision to be blurry it rarely causes any permanent damage to the health of your eyes.
If you experience blurred vision, headaches or eye strain, having a complete eye exam may lead to a diagnosis and treatment of this easily-dealt-with condition.
Article contributed by Dr. Jonathan Gerard
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