The most common cause of gradual onset bilateral blindness in the developed world is macular degeneration which is more common in non-insulin dependent diabetics.
Diabetic retinopathy is the second most common cause.
Other causes include:
- diabetic maculopathy
- hypertensive retinopathy
- chronic glaucoma
- chiasmal or bilateral optic nerve compression
- bilateral optic nerve damage, e.g. tobacco amblyopia
Worldwide, chlamydial infection causing trachoma is a common cause.