In essence, combining corneal collagen crosslinking (CXL) with LASIK is a relatively new procedure that aims to strengthen the cornea, thereby improving the stability of spectacle power after surgery, as well as potentially reduce the risk of a complication called corneal ectasia. In other words, this extra step aims to reduce the risk of spectacle power returning after LASIK as well as reduce the risk of a rare complication.
The exact threshold of pre-LASIK spectacle degree and post-LASIK remaining corneal thickness that will prompt a surgeon to suggest CXL can vary slightly, depending on other factors like corneal shape and individual surgeon practices. This is because the exact thresholds beyond which we start seeing large benefits with simultaneous CXL are not yet well defined in large studies.
In your case, your pre-op ‘spherical equivalent’ (or ‘overall power’) is 812.5 (750+125/2) on the right and 875 (850+50/2) on the left, and it is possible that your doctor has drawn up a protocol whereby your left eye has crossed the threshold beyond which he deems it beneficial to include CXL.
Even though your question whether ‘it’s really necessary’ or not is a perfectly natural one to ask, it is not something that can be directly answered because no one can predict if you are one of those people who are going to have the spectacle power return or not. Some do, and others don’t. But what we know from the studies is that in general, people with high powers have a higher tendency to have spectacle power return, and CXL will reduce the chance for that. Bearing that in mind, you have to discuss with your doctor and consider for yourself, whether reducing this risk is worth the extra money paid, or not.
