Why can’t an eye transplant cure blindness?
Because we don’t have the knowledge or capability to reconnect the optic nerve that transmits images to the brain. It’s still too complicated for current medical science.
These people are very right about the optic nerve being a big roadblock in the idea. But blindness can be caused by factors other than anatomical features of the eye. For example, the eye and nerve might be totally fine and working but there is an issue with signal transmission in the occipital lobe and the sensory information never gets processed. Even if you could attach the optic nerve perfectly
Think of it like a string of Christmas lights. One bulb goes out and they all go out, then you have to track down that one bulb that’s causing the problem to get them to all work.
With vision it may not be the eye that’s the problem, maybe it’s the optic nerve, the lateral geniculate nucleus, the optic tracks, or occipital lobe. Lesions in any of these areas can lead to blindness.
Most of the common causes of blindness do happen in the eye itself, (glaucoma, cataracts, diabetic retinopathy, etc), but like others have said we still can’t re-attach the optic or occulomotor nerves that would allow an individual to see normally if they were to receive an eye implant. Maybe sometime in the future, but not yet.
Optic nerves do not regenerate.
Even if you transplanted the eye and attached the blood vessels and muscles so it looked and moved normally, the nerves woyld not transmit the retinal image to the brain.