It’s important to differentiate between cataract surgery and Refractive Lens Exchange (RLE) when answering this question. Cataract surgery is a procedure designed to safely remove the cloudy lens and replace it with a clear lens with a goal of clear vision with glasses. RLE is a procedure designed to safely remove the lens (whether it is cloudy or not) and replace it with a clear lens with a goal of clear, focused vision without glasses or contacts.
What are the goals of cataract surgery and RLE?
If you look at those two different descriptors, you can see that they both have a goal of clear vision. Only one of them has the goal of clear and focused vision. The difference between these two can get muddled because there are so many factors involved. Chief among them is that cataract surgery often results in focused distance vision without glasses. Glasses for reading, however, should be expected to always be necessary after cataract surgery.
The main contributors to glasses-free distance and near vision — the goal of RLE, but not of cataract surgery — are the correct choice of intra-ocular lens (IOL) power and the correction of astigmatism. Those patients with focused distance vision after cataract surgery are those who have the correct IOL power and who happen to have no astigmatism after surgery (usually because they had none before). To have focused distance and near vision requires more than just those two pieces of good fortune, however, because it requires pre-operative planning for IOLs that are targeted to see distance and near without correction.
Hopefully that clarifies the difference with RLE because it’s the reason that RLE after corneal transplant is (almost) always not possible. Corneal transplants usually are prone to quite a bit of astigmatism of all kinds. That complicates both of the two main contributors to successful RLE. It complicates calculating and then intra-operatively laser scanning to determine the correct power for the IOL. On top of that, it is usually difficult — to the point of impossibility — to correct all of the irregular contours of the corneal transplant that create astigmatism.
What about cataract surgery after a corneal transplant?
If I could be presumptions enough to change the question a little, however, I think I could give a cheerier answer. Can I have cataract surgery and use some of the techniques of refractive surgery to decrease my need for glasses dramatically? The answer to that question is usually going to be yes! So it’s a bit of bad news / amazing news. The goal of RLE — no glasses necessary — is usually not achievable after a corneal transplant. But the amazing news? We can often achieve the goal of tremendously upgraded vision with decreased glasses dependence, or even glasses independence in some cases. Elective RLE may not be recommended, but when it comes time to get rid of your old lens and upgrade to a new one, chances are you’ll get vision that looks so beautiful and miraculous it’ll feel like it was worth the wait.