Astigmatism and Cataract Surgery
Astigmatism is a condition where the parts of the eye that focus images are imperfect, resulting in blurred vision. This is similar to nearsightedness or farsightedness, and can be corrected by glasses or contact lenses. Astigmatism is very common and can change over time as your natural lens changes with age. After cataract surgery, astigmatism does not typically change significantly.
Determining how much astigmatism needs to be corrected is based on measurements of the cornea. Some people have astigmatism that is caused mainly by imperfections in the natural lens. They have very little corneal astigmatism. In this case, taking out the cloudy lens (cataract surgery) will address most of the astigmatism and no further treatment of astigmatism may be needed. In other cases, the astigmatism is mostly in the cornea, and taking out the lens will leave astigmatism that will need to be addressed with glasses, contacts, an astigmatism correcting lens implant or reshaping the cornea.
Unmasking of astigmatism:
In some people, preoperative astigmatism in the cornea and the lens neutralize each other. If the astigmatism is oriented in in one direction in the cornea, and in the opposite direction in the lens, these can cancel each other out. In this case the patient may never have needed astigmatism correction in glasses or contact lenses before cataract removal. When the lens is later removed during cataract surgery, the astigmatism in the cornea can become evident as the lens is no longer present to neutralize the corneal astigmatism. This is how corneal astigmatism in some patients becomes unmasked. In this case a patient who has never had astigmatism in their glasses or contact lens prescription may have corneal astigmatism unmasked by cataract removal. This is determined before surgery with measurements and mapping of the cornea. This astigmatism can be corrected in the eye itself (with an astigmatism correcting lens implant or corneal reshaping with LRIs depending upon the amount of astigmatism). Alternatively, astigmatism can be corrected outside of the eye in glasses or contact lenses.
