Loss of/distorted central vision, difficulty seeing detail

Although this may be due to a need for a change in glasses (refractive error) or cataracts, these symptoms often indicate problems with the macula part of the retina.

Onset over weeks or months in the elderly is often due to dry age-related macula degeneration.

In younger age groups it may be due to diabetic eye problems, epiretinal membranes, macula holes or other causes of macula oedema.

Sudden reduction in one eye may be due to a blocked vein (retinal vein occlusion) or artery (retinal artery occlusion) or wet age-related macula degeneration.

There are also many rarer causes including:

Optic neuropathy
Trauma
Retinal detachment
Retinal dystrophies
Toxicity to the retina or optic nerve from medication
Tumours inside the eye