The question is, how would it be treated?
On the extreme end, the eye may need to be removed altogether. In addition to common terms I've tried searching for enucleation and evisceration, historical and medieval, and although plenty of articles mentioned that it existed (I've seen several mentions of it in ancient Egypt/China, and that there was a Chinese god "devoted to the profession of ocularists") but little about what procedures might be used. Searching for procedures or treatment often gives only a mention of the history in an article largely about modern procedure. Supposing they just hack/spoon the eye out, what options are there for preventing infection or closing the wound? Some sort of alcohol seems likely for cleaning; would mead work, since honey is also supposed to have antiseptic properties? And should they just stitch the eyelid shut in that case?
It sounds somewhat easier for the scratch to be just deep enough to cause a loss of vision, but not so much that the eye is totally destroyed and needs to be removed to prevent infection - although infection seems to be likely enough even with a scratch. Again, most information I was able to find on this was modern, or related to eye infections (cat scratch fever can manifest in an eye infection, which makes searching on those terms virtually useless) . If there was some way of disinfecting the wound (again, suggestions are welcome - I'd prefer to use a historical remedy, herbal or otherwise), would anything else need to be done to the eye itself to prevent other major complications aside from vision loss?