I think I'd rely on your vet in this case. There is SOME use in iridiology but there's an awful lot of B***S*** as well!! I remember a former employer of mine getting one in to look at a 4 year old with serious behavioral problems. After lots of gazing into his eyes she decided he had a problem with his near fore. When a huge splint (that you could see from across the field) was pointed out to her she concluded it was probably that she was seeing in his eyes!
She could find nothing else. Six months of dangerous behaviour and equally quacky alternative practitioners looking at the horse - he was put down. On PM, a large brain tumour was found! Sadly I'd left by then so didn't have the satisfaction of telling her I'd TOLD her that was the most likely cause a month before she started spending a small fortune on quacks!