Wednesday, April 20, 2011

Toric Lens Implant for Low Astigmatism

Question: I'm in a quandary about having a toric IOL lens verses a monofocal for one eye that has astigmatism of .75. I've seen two top surgeons in my area, one who says even though my dominant eye has .75 astigmatism, he would place a toric in that eye for optimum correction to have the best results. The other says emphatically that he will not put in a toric in that eye, that it isn't needed. The other eye would be a standard monofocal as it reads .50. I want the best vision possible and if a toric would tweak my vision at all I would do it, if the consequences are minimal. What should I do?

Answer: Astigmatism correcting lens implants (IOL) are very useful for providing Cataract patients with excellent vision at distance. Your Cataract Surgery poses an interesting question because of the small amount of astigmatism. There are really a few other factors other than the amount of astigmatism that can impact the decision of the Cataract Surgeon as to whether to use a toric IOL to correct low amounts of astigmatism. It’s not just based on the degree spectacle correction of astigmatism but also depends on the orientation of the astigmatism-whether it is stronger “vertically” than “horizontally” and what impact or degradation that has on your vision. In addition the decision can depend on whether the astigmatism is located in the cornea or the crystalline lens, which is being removed during Cataract Surgery. There has to be a quantitatively rationale relationship between the amount of astigmatism on the cornea and the total amount in your prescription. If all or most of the astigmatism is in your crystalline lens and this lens is being removed during surgery then a toric lens might be the wrong choice. Further, with such low amounts there may very well be some “astigmatic effect” created by the surgical technique itself. That is to say where the corneal incision is placed-what orientation and what length may induce or reduce small amounts of preexisting astigmatism. So it is entirely possible that the two top Cataract Surgeons you have consulted are giving you the best answer “in their hands”. They may very well use slightly different surgical techniques and in the case of Cataract Surgeon #1 he performs “astigmatically neutral” results and would need the toric IOL to provide the correction whereas Cataract Surgeon #2 might perform a procedure that causes a very slight reduction of the astigmatism as an artifact of his technique. If they are top Cataract Surgeons they both track their outcomes on a statistical basis and know very well what effect their surgical technique does or does not have on inducing, reducing or not effecting preoperative astigmatism. Thus, choose the top Cataract Surgeon you are most comfortable with and go with his recommendation.

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