I have not done any form of cross-linking (CXL) because it wasn't available when my keratoconus (KC) was still progressing. And I am not a medical professional.

CXL is performed in one of two ways: epi-off and epi-on. In epi-off CXL a thin layer on the front of your cornea is removed. In epi-on CXL the cornea is left as is. Then riboflavin drops are applied to your cornea and it is exposed to UV light. This causes the collagen in your cornea to cross-link and become stiffer. The riboflavin needs to soak into your cornea for this to work. The proponents of epi-off CXL think it is necessary to remove the front layer of the cornea so the riboflavin drops can penetrate the cornea thoroughly. The proponents of epi-on think they can get sufficient penetration without removing the front layer. The studies I've looked at seem to say that if epi-on is performed in certain ways it can be almost as effective as epi-off at stopping the progression of KC. The advantages of epi-on are that it is less painful and the recovery is quicker.

In the US, only the Avedro epi-off CXL procedure is FDA approved. Insurance coverage for CXL is not 100% yet. But the Avedro CXL procedure is the most likely to be covered by insurance. One could reasonably ask why Avedro pursued epi-off rather than epi-on if they are equally effective. Patients prefer epi-on if they have an opinion about it. Avedro sells the riboflavin and the UV equipment, so they should be indifferent to epi-off or epi-on. Presumably Avedro decided epi-off was more likely to demonstrate the effectiveness necessary to gain FDA approval when they began the time consuming and expensive clinical trials necessary to gain FDA approval.

Holcomb C3-R CXL is a proprietary form of CXL performed by Dr. Brian Boxer-Wachler of Beverly Hills, California. Dr. Boxer-Wachler aggressively promotes himself as a celebrity doctor. Some people find this off-putting. Others find this reassuring. Unfortunately this clouds the opinions of his work because it can be difficult to tell if the opinions about Holcomb C3-R CXL are being colored by opinions of Dr. Boxer-Wachler himself. I will just say that his website has a lot of verbiage about his procedure but I am unable to find any reference to peer reviewed controlled studies of his procedure. Hopefully there will be patients of Dr. Boxer-Wachler here who will share their experiences, good or bad.