What is Nyctalopia?

Medically reviewed by Tina Patel on 25 January 2023

Nyctalopia or night blindness is the inability to see well at night or when in poor light. For instance, someone with night blindness will have difficulty reading a menu or seeing around them in a dimly-lit restaurant. It is important to note that night blindness is not a disease, it is rather a symptom of a retina-related problem. It is a common misconception that night blindness or nyctalopia means that you cannot see anything at night, which is not true, it means that the person will have difficulty seeing things around them. It is usually common for people with myopia to experience difficulty with night vision.

If you have this symptom, you are more likely to find it difficult transitioning from light to dark or the other way round.

Night blindness symptoms

Night blindness is a symptom in itself. However, if you have night blindness, you might also experience the following:

• Blurry vision
• Cloudy vision
• Poor peripheral vision
• Difficulty seeing things at a distance, such as traffic lights
• Difficulty in transition from dim to bright light or vice versa
• Headaches
• Photophobia or sensitivity to light

You can also try out our Vision Stimulator Tool, that might help you understand if you have or are starting to develop any eye problem. The test let’s you experience the effects of astigmatism, myopia, presbyopia and hyperopia with our Vision Simulator which can be corrected using contact lenses or glasses.

What causes night blindness?

A few conditions can cause night blindness:

• Myopia or near-sightedness – a condition when the person can see nearby objects clearly, but the far away objects appear blurry.
• Cataracts – when the lens of the eye becomes cloudy, those with this condition see life as if through frosted glass.
• Retinitis pigmentosa – a condition that includes a group of degenerative and inherited eye disorders that cause severe visual impairments.
• Usher syndrome – a genetic condition that affects both hearing and vision.
• Glaucoma - a group of neurodegenerative eye conditions that affect the eyes optic nerve.
• Other eye conditions such as diabetes or Vitamin A deficiency can cause night blindness too.

How eyes work in dark?

Let’s understand how our eyes works in the dark. It is important to understand that our eyes work on the principle of refraction, meaning light plays a significant role to form an image at the back of our eyes, which in return helps us to see clearly.

In general, when there is low/no light, the pupils (the black hole in the eye) expands/dilates to let more light in to reach the retina. In bright light conditions, the pupils contract or get smaller, allowing only limited light to pass through and form an image on the retina.

Once the light enters the eye through pupil, it passes through the lens to focus onto the retina to form the image. However, when the light is low, it is harder to create the image.

The retina (spart of the eye on which the image is formed) consists of rods and cones cells that absorbs the light and convert it into an image to pass onto the brain. Rods have high sensitivity to light and are great at absorbing and processing light. Whereas cones have low sensitivity to light, they help us see details and colours, but both the cells need loads of light to work.

In the case of night blindness, when there’s not enough light for any of the above parts to utilise, they are unable to create an image properly, causing night blindness.

Night blindness diagnosis

Since night blindness can be caused by a range of eye conditions, your optometrist will perform different tests to filter out the potential conditions causing this problem. Your optometrist will enquire about any family history of eye conditions. The tests can include:

• Testing pressure in your eyes (tonometry), this test can help rule out glaucoma.
• Snellen test – an eye chart test to see if you’re myopic or hyperopic.
• Visual field test – this test assesses the sensitivity of the central and peripheral vision, which is a common symptom of night blindness.

Night blindness treatment

You may be asked to go for a blood test, where a blood sample will be taken to measure your glucose and vitamin A levels. Accordingly you will be prescribed with appropriate medication. Your optometrist might also recommend using contact lenses or glasses, depending on the results of your test.

How can I prevent night blindness?

Night blindness or nyctalopia cannot be prevented. It could be genetic such as with usher syndrome (affects vision and hearing) or can develop as a result of an eye condition. Here are some general ways to maintain your eye health:

• Eating a healthy diet and monitoring your blood sugar level is recommended. Sources of Vitamin A, such as spinach, carrots, pumpkins, cantaloupes, butternut squash, milk and eggs should be included in the diet.
• Go for regular eye exams. The NHS suggests going for eye exams every two years or as per advised by your optometrist.
• Wearing Sunglasses shields your eyes from UVA/B rays, which can increase your risk of cataracts, macular degeneration and glaucoma. Make sure to purchase sunglasses with UVA/B protection.
• Eye exercises may lower eye pressure and blood glucose levels.

If you’re struggling to see whilst you’re driving at night, or cannot see things around you in a dimly-lit environment, or you can’t transition when you come from a bright sunny day into your house, that’s your cue to book a sight test. Remember, night blindness can be a sign of a serious eye disease.