Herpes zoster ophthalmalacus
[Yes, “herpes of the eye” is a real thing. It’s actually multiple things.]
Herpes zoster, the virus that causes chicken pox and shingles, can infect the fifth cranial nerve, causing ocular manifestations (corneal inflammation and intense pain) and facial shingles. It’s considered an ophthalmic emergency, as permanent damage can be caused to the ocular nerve and eyeball.
Herpes simplex, the virus that causes oral and genital herpes, can also infect the eye, causing herpes keratitis, which is also an ophthalmic emergency. Both eye infections can cause scarring along the visual axis, and permanent vision impairment, and generally have to be treated with antiviral pills and eyedrops.
Atlas of the External Diseases of the Eye. Dr. O. Haab, 1899.