Astigmatism is a relatively common vision condition—almost everyone has it to some extent. Some people are hardly troubled by it at all, while others must undergo treatment for it because it is so severe.
A perfectly shaped eye is spherical; eyes with astigmatism are longer and more like a football than a globe. This improper formation causes headaches, eye discomfort, and blurred vision because light cannot focus the way it’s supposed to on the retina (the part of the eye that is sensitive to light). Where it normally bends evenly upon entering the eye, the light goes toward one direction more than the other in an eye with astigmatism.
Instead of a single point of focus, there are many, and only one part of the object being looked at can be clear at a time. This type of issue is called a “refractive error,” and it is not only similar to but often occurs in tandem with myopia (nearsightedness) or hyperopia (farsightedness). Exactly why so many eyes are formed this way has yet to be discovered, although eye injuries and surgeries can sometimes be at fault.
Astigmatism Types
There are three recognized types of astigmatism: myopic, hyperopic, and mixed. Dr. Gary Heiting, ophthalmologist, explains that every eye has meridians. If you picture an eye with a line through the center in either direction, you can also picture each meridian. When the eye is not spherical, “one meridian [is] significantly more curved than the meridian perpendicular to it.” The “principal meridians” are those that are “steepest and flattest,” according to Dr. Heiting. In myopic astigmatism, the principal meridians are nearsighted, while hyperopic astigmatism means they are farsighted. In mixed astigmatism, one principal meridian is myopic while the other hyperopic. The degree to which each meridians are myo- or hyperopic varies.
Whether the principal meridians are perpendicular (ninety degrees apart) also helps to classify astigmatism as regular (perpendicular) or irregular (not perpendicular). Corneal astigmatism occurs when the cornea (the clear cover of the eyeball) is irregularly shaped, while lenticular astigmatism means the lens of the eye is incorrectly curved. Regular corneal astigmatism is the most common.
Astigmatism Diagnosis
Experts recommend most people have a thorough eye exam at least every two years, starting as a child. If eye problems, health issues that cause eye problems, or a family history of eye problems are present, this time frame is decreased to every year. At these annual or biannual exams, a series of tests are performed; machines check eye pressure, a visual exam rules out things like cataracts, and the ability of the eyes to see close up, far away, and as a pair are tested.
Through these, your ophthalmologist will be able to tell if you have astigmatism, even if you haven’t noticed any issues. Astigmatism can begin in very young children or develop slowly, so it is extremely important to inform your doctor if you have noticed any change in vision, increased eye strain, or headaches, as these can tip her off to potential problems.
Astigmatism Treatment
The good news about regular astigmatism is that it can be corrected with contacts, glasses, or surgery. However, since it doesn’t always cause any visual problems, these may not even be necessary. When it is, your ophthalmologist will write a prescription for a certain corrective level of contact lenses or eyeglasses.
Irregular astigmatism, since it is generally caused by more severe issues, may require rigid gas permeable contact lenses, which let more oxygen reach the eye than normal lenses, allowing for healthier eyes. Refractive or laser surgery on the eye changes the shape of the cornea, fixing the astigmatism with no need for daily corrective lenses. Each case is different, so your ophthalmologist will guide you through the process of choosing the best option for you and your eyes.
