There are dozens of English speaking doctors in Cancun and specialists of all kinds. Not that I am a total expert but if you want to send me a Private Message, I will be happy to try to refer one in the area of medicine that you need. These are highly educated people so it should not be a huge surprise since we have a big English speaking population. Or, you could post here that "I am looking for an English speaking Opthalmologist in Cancun", or whatever, and I bet you will get a reply/referral/recommendation or two. Good luck.