My mom was having her cataract surgery next week. The doctor suggested trifocal Lenses(Panoptix) for her. I was reading that at 1.5 and above Toric should be used to correct astigmatism. Was hoping to hear thoughts on the same.
For reference, this is her prescription power - https://imgur.com/a/zqRb6Lf
You have to be careful in using eyeglass prescriptions to predict what astigmatism correction is needed for an IOL. Your eyeglasses have to correct for astigmatism in your lens as well as astigmatism in your cornea. If all or most of the astigmatism is in the lens, then that lens and the associated astigmatism is removed when the lens is removed. Sometimes the opposite can happen. The astigmatism in the lens can reverse the astigmatism in the cornea. Then the astigmatism gets worse when you remove the lens. The bottom line is that the only way to predict the required cylinder correction is to measure the topography of the cornea. That is what the IOL has to correct for.
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When you have the astigmatism for the cornea the minimum amount normally corrected is about 1.0 D. The manufacturers would like you to go lower, like down to 0.75 D. However, the basic problem is that the minimum power of cylinder correction in the IOLs is 1.5 D. If you put a 1.5 D correction in an eye that needs 0.75 D, then all you really do is reverse the angle of the astigmatism. You have spend the extra money and really done nothing. If you have 1.5 D of cylinder then that is the perfect amount for a toric lens. But, it has to be in the cornea not the lens and cornea combined.
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There are other options to correct astigmatism such as Limbal Relaxing Incisions (LRI) or Lasik. They would normally be used to correct smaller amounts while a toric lens for larger amounts. Another thing to keep in mind is that a small amount of astigmatism can help with close vision in a monofocal lens. I have a monofocal with the power for full distance vision. My post surgery eye prescription is 0.00 Spherical, and -0.75 Cylinder. However I can read down to about 18". I credit some of that to the residual astigmatism. Some surgeons report that patients who have LRI done sometimes complain about the loss of closer reading vision.
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The other bit of an issue to consider is that the surgery itself can cause some astigmatism. My surgeon said he measured my eye using two different methods pre op and got 0.0 Cylinder with one method, and 0.4 Cylinder with the other. My post op astigmatism came out to be 0.75 D, so the incision obviously made it worse. However, neither of the methods suggested enough to use a toric.
Hope this isn’t too late to be helpful. There’s an interesting article (search Astigmatic effect from phaco incision placement by Uday Devgan) that talks about the effect astigmatism direction has on results from surgery. Basically, where the doctor makes the incision and the direction of the astigmatism can either improve or worsen an astigmatism caused by the cornea.The location used by most doctors for the incision can improve “Against the rule” (side to side) astigmatism, while “With the rule” (up & down) astigmatism may get worse. Another thing the articles mention is that “with the rule” astigmatism tends to change with age to “against the rule”, so if they leave a little bit of “with the rule” astigmatism the patient can have more years with minimal astigmatism.