REALLY NEED HELP! massive blunt blow eye/cornea (horse)

On Sept 1, 2016 our horse hit his right eye on grain bucket (with 20 pound salt block). It was a very bad bruise to cornea (as per vet) and gray shading in middle of eye developed and is growing. In November 2016 we were able to clear it up with Ledum 30c, it came back in January 2017 and we can not clear it up. We tried Ledum 30c (5days on 2 days off) same with Ledum 100c and one dose only Ledum 1m, nothing happened. We have tried 30c Silcia 5 days and no change, we tried 5 days 30C ( Symp + ledum + arnica mixed in wet dose) and not much, got a very small bit better. March 25, 2017 we tried one dose 200C Echinacea, and no change. We have been working with our vet through all of this and she has prescribed Maxitrol steroid eye drops and pulsing dose of Banamine, usually at 14 day course. This horse loves his food, drinks lots of water, loves his salt lick, is bold, higher up in pecking order, loves people and is a rescue horse, he is half Arabian and half thoroubred, 12 years old. Any suggestions on what to try ? I have been taking pictures every week so that I can see any changes. He was vaccinated for Rabbies & tetnus on August 30, 2016 when the vet first came out to see the eye. He was wormed in January 2017. The eye has never been cut, no ulcer, just severe blow to cornea, as per vet, eye hs been stained twice to confirm, he wears a UV mask when outside. I am so stressed, and nothing is working. I do not understand why Ledum worked in November 2016 and does not work after that ?
[message edited by Eisa on Tue, 28 Mar 2017 12:30:13 UTC]
[message edited by Eisa on Tue, 28 Mar 2017 12:32:36 UTC]
[message edited by Eisa on Tue, 28 Mar 2017 17:09:40 UTC]
[message edited by Eisa on Tue, 28 Mar 2017 17:10:12 UTC]