OP I used Leanne Wrentmore from Naturally Horses. She was brilliant - I sent very detailed photos of my boy's eyes, these photos must be high quality taken in a stable out if bright light to avoid reflections.
Everything she said in her report was later substantiated by Sue Dyson at Newmarket. I was extremely pleased with the information and accuracy. The website advises about photo quality. Good luck.
Maybe not. My mum had her cataracts done and the surgeon told her there was a surprising amount of illness in the human body that could be diagnosed from inspection of the iris.
The danger comes when people jump on the bandwagon and claim all sorts fraudulently for their own profit. You see that in all walks of life.