Overview
Colour vision depends on three types of cone cell in the retina. When one type is missing or shifted in sensitivity, certain colours become hard to distinguish. The common inherited form affects reds and greens and is carried on the X chromosome, which is why it affects far more men than women.
Most people with it see colour; they simply confuse particular pairs. Total absence of colour vision is rare. Acquired colour changes, especially in one eye only, are a different matter and worth investigating.
What are the common symptoms?
- Confusing reds with greens, or blues with purples
- Difficulty with colour-coded charts, wiring, or maps
- Trouble judging ripeness, rashes, or whether meat is cooked
- In children: mislabelling colours, or difficulty with colour-based schoolwork
What causes it, and who is at risk?
- Inherited, X-linked — around one in twelve men and one in two hundred women
- Acquired causes: glaucoma, macular degeneration, optic nerve disease, cataract
- Some medications, and long-term exposure to certain chemicals
How is it treated?
Inherited colour deficiency cannot be cured, but it can be worked around, and it is worth confirming formally — some careers require a specific test result.
- Formal testing to establish type and severity
- Colour-filtering glasses or contact lenses, which help some people distinguish specific pairs, though they do not restore normal colour vision
- Practical adaptations: labelling, apps, and relying on brightness and position cues
- Investigation of the underlying cause if the change is recent or affects one eye
When to get seen quickly
Colour vision that changes suddenly, or that differs noticeably between your two eyes, is not inherited colour blindness. Get it checked promptly — it can signal optic nerve disease.
This page is general information, not a diagnosis. Only an eye care professional who has examined you can tell you what is actually going on.