Dimmed vision feels as though brightness has been turned down, even in normal lighting. It can signal retinal, optic nerve, or systemic issues.
Possible Mechanisms
Ischaemic optic neuropathy, retinal vascular occlusion, advanced macular disease, and widespread retinal degeneration can all reduce perceived brightness. Anaemia, low blood pressure, and systemic hypotension may cause transient dimming on standing.
- Sudden dimming in one eye is concerning for optic nerve or vascular events
- Gradual dimming with night-vision problems suggests retinal disease or cataract
- Some medications affect pupil size or retinal adaptation, altering brightness
- Neurological conditions can cause bilateral dimming with normal eye structures
Assessment
Evaluation includes acuity, pupils, colour vision, fields, and imaging of the retina and optic nerve. Systemic examination may be needed for vascular or haematological causes.
- Urgent referral is appropriate for sudden unilateral dimming
- Managing systemic risk factors reduces further events
- Low-vision services can help where dimming is irreversible
- Patients should report any associated headaches, jaw pain, or scalp tenderness promptly
