Approaches to cataract surgery vary in patients with previous refractive surgery. John A. Hovanesian, MD, FACS, interviews Douglas D. Koch, MD, about performing cataract surgery on patients with prior refractive surgery.

An excerpt from the article:

Hovanesian: Why is it so difficult to measure the cornea of post-refractive surgery patients?

Dr. Koch: There are two reasons that it is difficult to obtain good corneal measurements in patients who have had prior refractive surgery. We must remember that the cornea has two curvatures, a front and a back, and when we use a standard keratometer or topographer, we are only measuring the front, but we are giving an overall value for corneal power. That overall value is based on some assumption about what the back corneal power is. If you subject a patient to PRK or LASIK, you change the front corneal power but not the back, and so you alter the relationship. These devices use a different index of refraction to compensate for the back corneal power, but if you change the relationship between front and back, that index of refraction is no longer valid.

Unfortunately, because different levels of correction change the front in different magnitudes relative to the back, there is no new single value for refractive index you can just plug into those machines to get your true corneal power. So what we are doing is measuring the front and having to make a sophisticated guess about the back, and that guess is often not as accurate as we would like it to be.

Read the entire interview here:
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I've been told be several surgeons that too many refractive surgeons do not have any idea about the problems because they, themselves, do not do cataract surgery. It is, however, possible with the proper calculations, to get a much closer prescription. When a patient develops cataracts and sees a surgeon, that surgeon could then call upon another ophthMD who specializes in doing the calculations.
That is a very good explanation doctor. Corneal power was our topic this morning in my major subject and I found out that the words of my professor are supported by what you have said. There are two curvatures of cornea that is why we can't measure the cornea easily.
This article may help to explain the difficulties encountered when measuring for IOLs after LASIK surgery:

Intraocular Lenses Powering up new IOL calculations for post excimer laser patients

One of the biggest problems is the cataract surgeons, themselves, who are often totally unaware of the issues caused by laser refractive surgery. While new tools are now being developed, there is a large group of patients whose clear vision, already damaged by LASIK, is now irretrievably ruined by bad cataract surgery. Amongst these patients, many cannot be helped by glasses or contact lenses.

Until all cataract surgeons become familiar with the new tools and the new rules, we will still have the uncertainty that comes with cataract surgery.
doesn't sound at all about the cataract IOL problem, I think now day there are new technology and software that can measure cornea, but you have to search who has one. I hope someday they will have this thing nail down where all the post lasik people don't have to suffer like this no more.
It doesn't sound good about this post lasik and cataract problem where doctors have problems dealing with this IOL problems for post lasik cataract people. I think now day they have some machines that are on the market that can calculate and measure the cornea for a accurate IOL but you have to do a lot of research to find out where the doctors are and their machine.
Unfortunately, there is no such machine available. Even the best surgeons hit and miss. The problem is not going to go away, and as more people who have had refractive surgery age and develop cataracts, the problem will become widespread.

No amount of research to find the "right" doctor or machine will change the reality of what is.
VSRN is in touch with patients facing cataract surgery post-corneal refractive surgery. This is not a matter of measuring the cornea since post-RS corneal measurement is not the sole factor in IOL calculations. This issue has been in question soon after LASIK was introduced and countless surgeons have prophesied the ultimate formula. TO DATE, THERE IS NO ULTIMATE FORMULA. This is why Barbara started the thread, to discuss the issue and offer a spot for others to post their experiences.

Reality check: There is no "machine" and finding someone on the internet who purports to have technology that nails the IOL calculation is to be considered suspect. If such technology and formulas were accurate, you wouldn't have to research doctors who have it. Such technology would be verifiably effective at producing good outcomes and would move into the mainstream via the normal channels.

Again, beware of any doctor who purports to have THE methodology.

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