Robert Deck, an optometrist with Todd Harris and Associates in Lapeer, Michigan, performs routine eye examinations and assesses whether or not patients have focusing issues. To inform his work, Robert Deck of Michigan draws on an in-depth knowledge of nearsightedness and farsightedness, as well as astigmatism.
Astigmatism simply means that a patient's cornea or lens has an abnormal curvature. A normal cornea and lens are both perfectly round and feature equal curvatures in all directions, which allows light to enter the eye and focus cleanly onto the retina. In an eye with astigmatism, however, the cornea or lens develops a football-like shape that refracts light so that it focuses incorrectly and leads to blurry vision.
Most cases of astigmatism are due to an imperfection in the shape of the cornea. This imperfection may be due to myopia in one or both principal meridians, which one can conceptualize as the height or width of the cornea if the cornea were flat. Some think of them as the distance between 12 and six or three and nine, if the front of the eyeball is a clock face.
If one meridian is myopic (nearsighted), or if both are nearsighted to different degrees, the patient has what is known as myopic astigmatism. Hyperopic astigmatism occurs when one or both principal meridians are farsighted, whereas mixed astigmatism indicates one farsighted and one nearsighted meridian. An astigmatism may also be classifiable as regular or irregular, the latter developing when the principal meridians aren’t perpendicular.
Regardless of the type of astigmatism, most cases are treatable using corrective lenses or surgery. A corrective lens must be structured in a way that adjusts for the difference in meridian shape, though many patients can correct the issue permanently by undergoing a laser refractive procedure.
