Night blindness
Night blindness (also known as nyctalopia) is a condition that results in poor vision in low light or darkness. It is not a disease in itself, but rather a symptom of an underlying condition, usually a problem with the retina.
Pronunciation
- Night blindness: /naɪt ˈblaɪndnəs/
- Nyctalopia: /nɪktəˈloʊpiə/
Etymology
The term "night blindness" is derived from the Old English words "niht" (night) and "blindnisse" (blindness). "Nyctalopia" comes from the Greek words "nykt-" (night) and "-alops" (blindness).
Causes
Night blindness can be caused by several conditions and diseases that affect the retina, the layer of light-sensitive cells at the back of the eye. These include:
- Retinitis pigmentosa: a genetic disorder that causes progressive loss of vision
- Vitamin A deficiency: Vitamin A is essential for the health of the retina and a deficiency can lead to night blindness
- Cataracts: clouding of the eye's natural lens, which can cause a decrease in night vision
- Certain medications: some drugs can affect the retina and cause night blindness
Symptoms
The main symptom of night blindness is difficulty seeing in low light or darkness. This can make it hard to drive at night or navigate in dark places. Other symptoms can include blurry vision, difficulty adapting to changing light conditions, and seeing halos around lights.
Treatment
Treatment for night blindness depends on the underlying cause. This can include:
- Vitamin A supplements for those with a deficiency
- Surgery to remove cataracts
- Medications or gene therapy for conditions like retinitis pigmentosa
Related Terms
External links
- Medical encyclopedia article on Night blindness
- Wikipedia's article - Night blindness
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