Treatment of Astigmatism
There are two ways to reduce astigmatism during cataract surgery. One is to use a specially designed toric intraocular lens. The toric lens has more curvature in one dimension and less 90 degrees away- it has its own astigmatism. The principle is simple- the surgeon chooses a toric lens with the same curvature discrepancy as the corneal curvatures, then rotates the lens inside the eye such that the steepest curvature of the lens aligns with the shallowest curvature of the cornea. When this is done, the total optical power of the eye in all dimensions becomes approximately equal- thus reducing or eliminating astigmatism.
The other method to reduce astigmatism is to directly change the corneal curvature with corneal refractive surgery (LASIK), or corneal incisions (limbal relaxing incisions).
Toric lenses are powerful devices that are useful for moderate and large amounts of astigmatism. Corneal refractive methods are better for smaller amounts of astigmatism. They can be used for small refinements after surgery.
Because at least one out of three patients will get a superior optical result if they manage their astigmatism, many surgeons offer toric lenses. Those who do not might have a referral relationship with a surgeon who does.
To review the optics of astigmatism, click here.