Many times a patient will return post-cataract surgery unhappy that they need to use bifocals to see clearly. “But my friend had cataract surgery and only needs glasses for reading,” is often heard. Certainly a pre-operative discussion and education of astigmatism with the patient is helpful, but being able to appropriately correct astigmatism is of equal importance.
Several options are available to the patient undergoing cataract surgery: limbal relaxing incisions (LRIs), toric intraocular lenses, and laser vision correction. In general, I will use LRIs for patients with up to 1.5D of astigmatism, toric intraocular lenses for patients 1.5D to 3D, and combine toric IOLs with LRIs for patients with higher levels of astigmatism. I reserve laser vision correction for patients following cataract surgery who need further astigmatic correction.
Most important in the pre-operative evaluation of astigmatism control is corneal topography. Manual keratometry alone will miss forme fruste keratoconus and pellucid marginal degeneration. Limbal relaxing incisions should never be performed in these patients, as it may cause destabilization of their cornea. Of concern is in a recent quiz on ophthalmologyweb.com, nearly 50% of respondents failed to recognize keratoconus by topography and would recommended an intraoperative unpaired LRI to try to improve astigmatism.
If topography reveals normal astigmatism, LRIs can be performed at the slit lamp or in a LASIK suite. Nomograms by Drs. Nichamin and Donnenfeld are available at lricalculator.com. Of equal importance with topography is pachymetry; LRIs should be created at 90% depth. Less deep LRIs will not induce much change and deeper wounds risks wound gaping and possible perforation.
Laser vision correction, if selected to correct post-operative astigmatism, should be performed after the cataract wounds have healed and the refraction has stabilized. The decision to perform surface ablation vs. LASIK is up to the surgeon preference, as either of these can be successful.
In my discussion with patients I make sure to explain that correction of astigmatism is more of a “cosmetic” benefit, that they would see equally well with glasses but what they are paying for is to see more without them. Many times I will show the topographies to the patients so that they may better understand these concepts. By keeping the patient as educated as possible, I have been able to maximize the patient’s comfort and happiness with the entire experience. Recently I saw a patient who came in desiring a multifocal IOL. Refraction revealed moderate myopia with minimal astigmatism, but topography demonstrated 2.5D of astigmatism in a forme fruste configuration. After a lengthy discussion of risks, benefits, and alternatives, the patient agreed to monovision with toric intraocular lenses. He has done very well, and enjoys spectacle independence today.
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