# Night Blindness

Source page: https://www.kudretgozistanbul.com/en/treatments/night-blindness

**Author:** Kudret Eye İstanbul | **Medical Approval:** Op. Dr. Mehmet Ali Özdil | **Date:** 2026-09-16

> **Summary:** Night blindness (nyctalopia) is difficulty seeing in dim light or in the dark because the eye cannot adapt to darkness. It is a symptom of other conditions rather than a disease in itself, retinitis pigmentosa being one of its important causes, and treatment depends on the underlying cause.

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## What Is Night Blindness?
In a healthy eye, vision adapts quickly to dim light. In night blindness this adaptation fails: it does not cause complete blindness but vision is inadequate in weak light or darkness. The main cause is deterioration of the photoreceptor cells in the retina. The age of onset, progression and severity vary between individuals.

## Causes
- Myopia
- Cataract
- Diabetes
- Glaucoma
- Vitamin A deficiency
- Keratoconus
- Retinitis Pigmentosa (one of the important causes; it affects the photoreceptor cells of the retina)
- Usher Syndrome
- Some corneal surgeries and drug treatments

## Symptoms
- Inadequate vision and narrowing of the visual field in low light.
- Adaptation problems when moving from bright to dim surroundings.
- Light sensitivity and blurred vision after exposure to intense light.

When caused by inherited retinitis pigmentosa, symptoms and timing differ from person to person: they usually appear in childhood but can also begin in adolescence or adulthood. It affects both eyes, first narrows peripheral (side) vision and progressively reduces vision in low light; in advanced stages it can cause serious loss of sight. The rate of progression and degree of loss are hard to predict.

## Diagnosis
- A dark adaptation test measures the transition from light to darkness; a visual field test shows whether peripheral vision has narrowed; vision quality in dim light is analysed.
- Electroretinography and fundus examination to look for an underlying eye disease.

## Treatment
Treatment depends on diagnosing the underlying disease, so anyone with severe vision loss at night or in dim light should have a detailed eye examination.
- **Cataract or keratoconus:** Surgery may be an option. In cataract, replacing the clouded lens with an intraocular lens usually improves vision in dim light.
- **Keratoconus:** Hard contact lenses can improve night vision as well as refractive problems.