Night blindness

Night blindness, known medically as nyctalopia, is a condition in which your eyes struggle to adjust to low light. Whilst others can still see reasonably well at dusk or in dim lighting, you experience severely reduced vision. It is not complete blindness, but rather a significant reduction in your ability to see in low light.

Your eyes normally adapt to different light levels. In low light, the rods in your retina take over from the cones. The rods are sensitive to dim light and are responsible for your night vision. In night blindness, this adaptation mechanism does not work properly, often because the rods are damaged or do not function correctly.

Causes of night blindness

Night blindness can have various causes. Sometimes it is hereditary and congenital; sometimes it is caused by another eye condition or a deficiency in certain nutrients:

• Vitamin A deficiency: vitamin A is necessary for the production of rhodopsin, a substance in the rods that converts light into signals. A deficiency can lead to night blindness.
• Retinitis pigmentosa: a hereditary condition in which the rods in the retina gradually die off.
• Cataracts: clouding of the eye’s lens can impair vision, particularly in low light.
• Glaucoma: increased eye pressure can damage the retina and the optic nerve.
• Short-sightedness (myopia): people with severe short-sightedness sometimes find it more difficult to see in the dark.
• Diabetes: can cause damage to the retina (diabetic retinopathy), which can affect night vision.

Symptoms and recognition

You often notice night blindness in everyday situations: driving in the dark becomes more difficult, you trip more often in poorly lit areas, or it takes longer for your eyes to adjust when moving from a bright to a dark environment. Some people also perceive less contrast or find it difficult to judge distances in low light.

Night blindness is not a disease in its own right, but a symptom that may indicate an underlying cause. It is important to have the cause investigated by your optician, optometrist or ophthalmologist. Depending on the cause, it may sometimes be possible to treat it; for example, if a doctor diagnoses and treats a vitamin A deficiency, or by treating the underlying eye condition.

Contact lenses and night blindness

Contact lenses do not treat night blindness, but they can correct your general vision if you are short-sighted, long-sighted or have astigmatism. A good correction can help improve your vision in all lighting conditions. Some people with night blindness find that dirty or dry lenses further impair their vision in low light, so good lens hygiene and adequate moisturisation are particularly important in such cases.

Practical tips

If you suffer from night blindness, there are a number of things you can do to help you get about more safely and comfortably:

• Avoid driving in the dark if your vision is too limited, or only do so on familiar, well-lit routes.
• Ensure there is good lighting at home, particularly in hallways, on stairs and in the bathroom.
• Give your eyes enough time to adjust to the dark before you start moving around.
• Make sure your glasses or contact lens prescription is up to date; an outdated prescription makes it even harder to see in low light.
• Have your eyes checked regularly so that any changes can be spotted in good time.

If you have any symptoms or are unsure whether you have night blindness, have it assessed by your optician, optometrist or ophthalmologist. They can investigate the cause and advise you on the options available.