Astigmatism is a refractive error of the eye, but it is different than both nearsightedness and farsightedness. In a normal eye, light comes through the retina to form a single focus point. With nearsightedness or farsightedness, the light is unable to focus properly when looking at either near or far distances. Astigmatism, on the other hand, fails to create a single focus point, but instead has multiple that can be in front of or behind the retina.
Your eye doctor near Ellicott City, MD, may be concerned you have astigmatism if you struggle to see clearly at any distance. This refractive error is often accompanied with headaches, squinting and eye strain. There are also three primary forms of astigmatism.
Primary Forms
A normal eye is often thought of as being spherical, but an astigmatic eye is often more oval, or football, shaped. The eye is made of up meridians, which, if the front of the eye were a clock face, would be two lines: one connecting three and nine and another connecting six and 12. In astigmatism, whichever lines are steepest and flattest are considered the principal meridians. Understanding meridians is necessary when talking about the different kinds of astigmatism.
- In hyperopic astigmatism, the principal meridian, or sometimes both, is farsighted.
- In myopic astigmatism, the principal meridian of an eye, or sometimes both principal meridians, is nearsighted.
- In mixed astigmatism, one principal meridian is farsighted while the other is nearsighted.
Your optometrist may help you figure out what type of astigmatism you have.
Classifications
This refractive error is also classified in two different ways. First, regular astigmatism has principal meridians that are perpendicular, or 90 degrees, to each other. Second, irregular astigmatism has principal meridians that are not perpendicular to each other. No matter what type or classification of this refractive error you have, your eye doctor may prescribe eyeglasses as a way to combat this issue. Go to regular comprehensive eye exams to learn more.