Is corneal cross linking necessary to prevent my degree from returning after LASIK?
I have an above average cornea thickness of about 580 microns in each eye. The degree in my left eye is about 850, astig 50 and right eye is 750, astig 125.
My doctor has recommended me to do corneal collagen cross linking in only my left eye, which left me quite confused as the degree difference between both my eyes isn’t a big difference. Also, I have an above average cornea thickness, so I’m not sure if going for CXL is worth it because of the steep price.
Can I get some advice on whether I should go ahead with CXL, and if it’s really necessary to prevent my degree from returning?
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.
Thanks for this interesting questions!
The use of collagen cross-linking to enhance Lasik procedures has been performed increasingly commonly in the last 15 years.
This is due to more evidence emerging that at-risk patients show increased refractive stability over time. The patients who seem to show the most benefit are:
- Hyperopic, high-dioptre myopic corrections
- Patients with significant astigmatism or
- Patients with borderline thin residual corneal thicknesses.
The mechanism of action is to restore at least partially the rigidity of the anterior stromal fibres that were cut during Lasik flap creation.
As each patient deserves a customised treatment plan, you should discuss with your ophthalmologist whether you would be suitable for:
- Epilasik, Femto-assisted Lasik, or Smile and whether: primary or secondary collagen-cross linking as required is most suitable for you.
- Whether an Implantable Collamer Lens would be a refractive option that you would consider?
You should carefully consider the advantages and disadvantages of all these options before deciding on your surgery!
It is great that you are thinking about the long-term results of your laser vision correction. As you may already know, collagen cross-linking activates the collagen fibres within the cornea to cross-link and thus resulting in a stronger cornea. By strengthening the cornea after laser vision correction, it is hoped that the longevity of your laser results can be extended and at the same time, minimising the need of enhancement surgery in future.
Whilst cornea thickness does play an important part during a laser suitability evaluation, it is also important to note that it is not the only factor a surgeon will consider when recommending the need for collagen cross-linking. The surgeon will also look at other factors including the shape of the cornea and make the recommendation should he/she feels that there is some weakness in the cornea that may increase the probability of any degree from returning.