I have this guy slowly going blind but I don’t say why. It’s set in the second half of the 19th c, mostly during the civil war but then we pick up with him again later when he’s gone completely blind. Any insight would be appreciated.
If things are darkening in the center, it can be macular degeneration. Generally strikes older people. They don’t go completely blind as peripheral vision is retained, but they can’t see anything they actually look at, so reading is extremely difficult, as is recognizing faces, driving, or functioning independently. We still don’t have great treatments for this disease.
Cataracts are another possibility, and the most common cause of blindness worldwide. This is clouding of the lens and may be visible to others. The clouding develops slowly, causing faded colors, blurry vision, halos around light, and trouble seeing at night. Cataracts can be caused by eye trauma, but are most commonly due to aging, especially in those who drink alcohol, smoke, and/or have prolonged exposure to sunlight without eye protection. Treatment of cataracts has existed for centuries, but in the 19th Century it was very uncommon, and frequently lethal to operate on the eye.
Glaucoma damages the optic nerve resulting in vision loss. Most forms are caused by high pressure within the eye and it’s more common in those with migraines, high blood pressure and obesity. There’s also a familial component. It may develop slowly or rapidly and with or without pain. They may see halos around lights, have nausea and vomiting, and a pupil that doesn’t react to light. The vision loss is generally permanent, but can be prevented, though not in the 19th Century. The first surgical treatment was in 1856, and drug treatment in 1875.
Diabetic retinopathy is another relatively common cause of blindness. It starts with swelling around blood vessels in the back of the eye causing blurred vision, then progresses to formation of extra blood vessels that burst and bleed and further blur vision. All this can be prevented, or at least slowed, with good care and frequent examinations, but after 20 years of diabetes, 80% of patients will be affected to some degree.
For your character, glaucoma may be the best bet. But if you want him to still be able to get around, and just be unable to read or something, then macular degeneration might be a better choice… Good luck!