Please help! what is the most challenging ophthalmological conditions?

Two types: The first is macular degeneration, a plague upon the elderly as the cause is not known and there is no cure. The other types are inherited diseases with no cure which progress to severe vision loss such as retinitis pigmentosa.

Acute retinal necros: Ocular manifestation of systemic conditions like acute retinal necrosis. Intraocular foreign body and endophthalmitis

Neurological view: In my field irreversible loss of vision or blindness secondary to optic neuritis, can be seen mainly in Neuromyelitis Optica (Devic's disease), or to a less intense effect, multiple sclerosis. Would certainly defer to our excellent ophthalmologists who see a far wider spectrum of eye disease.