What is Nyctalopia?

Nyctalopia (also known as night blindness) is the inability to see well at night or in low-lit conditions. 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, but rather a symptom of a retina-related problem. It is a common misconception that nyctalopia/night blindness means that you cannot see anything at night – this is false. It simply 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 suffer from nyctalopia, you are more likely to find it difficult transitioning from light to dark or the other way around.

What is the first symptom of night blindness?

Night blindness is actually a symptom in itself. However, those who are experiencing night blindness may find they also have:

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

Our vision simulator tool might help you understand if you have (or are starting to develop) any eye problems. The test also lets you experience the effects of astigmatism, myopia, presbyopia and hyperopia.

What causes night blindness?

Causes for night blindness can vary, however, it is usually a symptom of an eye condition such as:

• Myopia or near-sightedness – when you can see nearby objects clearly, but far away objects appear blurry
• Cataracts – when the lens of the eye becomes cloudy (similar to looking 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-related conditions such as diabetes or Vitamin A deficiency can also cause night blindness.

How do our eyes work at night?

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

Here’s how it works

When there is no (or low) light, the pupils (the black hole in the eye) expand/dilate 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 the 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 (the part of the eye in which the image is formed) consists of rods and cone cells that absorb the light and convert it into an image to pass onto the brain. Rods have a 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 of 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.

What is the diagnostic test for night blindness?

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.

Can night blindness be prevented or cured?

Nyctalopia night blindness cannot be prevented. It may be genetic, such as with usher syndrome (affects vision and hearing) or can develop as a result of an eye condition.

If you suspect you have nyctalopia, a medical professional may recommend a blood test to measure your glucose and vitamin A levels. You will be prescribed appropriate medication if necessary. Your optometrist might also recommend using contact lenses or glasses, depending on the results of your test.

You should always maintain your eye health by:

• Having regular eye exams (every two years or as per advised by your optometrist)
• Eating a healthy, balanced diet and monitoring your blood sugar level
• Wearing sunglasses to shield your eyes from harmful UVA/B rays

If you’re struggling to see whilst driving at night, and/or cannot see things around you in a dimly lit environment, that’s your cue to book a sight test. If you’re not sure how and when to book an eye test, read our eye test guide to find out all there is to know. For general optical queries, feel free to get in touch with our expert optical team.