I can offer a few thoughts that MAY be of some use...
I have a good deal of experience with blindness, some animal, some human,
And a few things seem in common
Having to Adjust to a new and FRIGHTENING situation, especially when you (your Horse) uses sight as a major component to his survival abilities, can add to the stress.. In the case of people, after the Initial shock, then subsequent adjustment period, you (the person) would have to rearrange certain furniture (or stuff around the barn) so as to ease the transition to where trouble and ease of movement are now most Important. Moving things to easier and logical spots (can be trial and error, note where he is most used to finding these things, and make access easier)
You then will need to do a good deal of detective work, to see what you can imagine will be a bump or trouble area, clear it out of the way, and then while you are handling him, you also make it easier on yourself to help navigate him through areas that may become frightening. I believe part of the problem is the transition, and I known in most cases, and with tons of patience (you cannot allow yourself to get upset, or he will feed off of it) it can work.
It is very possible to carry it through..I would never say this is easy..It can take a good long time for him to make a hopefully full transition to this "new" environment, as it may seem like a new, and scary new environment to maneuver though. Try to Imagine as best you can, what it is like for him to be in this position, and as camly as you could possibly be, help to lead him SLOWLY through this process..
You might try some different thinking too, such as near to his stall, a radio softy playing classical music (anything not loud or stressing) and if he seems to not mind that, he may associate the music playing with security, and the exact postion of his stall...trying things out of the box, using some common sense, may work out to be beneficial..His ears will become enhanced soon, as that is natures way, and if you can work carefully with this enhanced sense, it should be of benefit...
I don't claim to know all about this subject, however patience to no end
Often brings on the desired results
I wish you Gods Blessings with this,
And I definitely feel for you here Lw