Eye's optical problem: perhaps asphericity?

Question

I am nearsighted but corrected, have hardly any accommodation capability, and have been told I have incipient cataracts. The optometrist says my retinas are fine. Over the past couple of years I have noticed a strange phenomenon: my corrected vision is pretty good at night and at light levels comparable to the optometrist's eye chart, but in bright light it gets blurry. I don't think it's because of cataracts (I don't notice any fogging) but it could be due to an asphericity of the lens or of the eyeball surface, which could cause the average focal length to change as the iris opening changes between wide and narrow. So my question is, would a lens replacement (the recommended remedy for the cataracts) fix the focus problem, or is eyeball surface asphericity a possible cause? Do cataracts change the lens shape? Are there other possible causes given that the retinas are healthy?

If you go to the trouble of answering this question, I'd appreciate your also bookmarking it (e.g., watch-list it) and revisiting it in case I have a followup question. For instance, I would want to know the reasoning behind an answer I don't fully understand. Thank-you.

Answer 1

If you have problems with accommodation, a solution might be a specific type of intraocular lens called apodized diffractive lens.
See this link: http://www.acrysofrestor.com/
This lens is similar to the ones that have been used for a long time for cataract surgery, but has specialized optics to give accommodative and refractive correction. This lens takes advantage of the phenomenon you describe about focal length changing with iris opening (pupil diameter) change and focuses the image where it needs to be (pseudoaccommodation). I don't know if asphericity or cataracts would cause this problem in your case or not. Cataracts can change the lens shape. They not only make it yellowish or cloudy, but hard or rigid, so it is harder to accommodate. Good for you for educating yourself so well on your condition!