Nyctalopia, also called night blindness, is a condition that makes it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases, such as retinitis pigmentosa cataracts, glaucoma, nearsightedness, vitamin A deficiency, and others. The problem comes from a disorder of the cells in your retina that allow you to see a dim light. Treatment depends on identifying and addressing the underlying cause.
Causes of nyctalopia
Nyctalopia can be caused by several eye diseases and other conditions. Some of these causes include:
- Retinitis pigmentosa (RP): a disorder in which the rod cells in the retina gradually lose their ability to respond to light.
- Cataract: a clouding of the lens that affects vision.
- Glaucoma: a condition where the eye's optic nerve is damaged with or without raised intraocular pressure
- Nearsightedness (myopia): a refractive error that makes distant objects appear blurry
- Vitamin A deficiency: a condition that affects the production of rhodopsin, a visual pigment in the rods
- Diabetes is a metabolic disorder that can damage the blood vessels in the retina and cause diabetic retinopathy.
Certain medications (e.g., phenothiazines, chloroquine) can affect the retina or the pupil size. Other eye diseases or injuries that affect the retina or the optic nerve can also lead to nyctalopia.
Signs and symptoms of nyctalopia
There are several signs and symptoms of nyctalopia, which may include:
- Difficulty seeing in dim light or at night
- Difficulty adapting from a well-lit to a poorly-lit environment
- Cloudy or blurry vision in low-light environments
- Seeing halos or glares around lights
- Squinting or rubbing eyes to see clearly
- Headaches or eye strain1
If you notice any of these signs, you should see a doctor for a proper diagnosis and treatment.
Management and treatment for nyctalopia
The management and treatment of nyctalopia depend on the underlying cause of the condition. Some possible treatments are:
- Getting a new eyeglass prescription or switching glaucoma medications if the cause is nearsightedness or glaucoma
- Having surgery to remove cataracts if they are affecting vision
- Taking vitamin A supplements or eating foods rich in vitamin A if the cause is vitamin A deficiency
- Controlling blood sugar levels and having regular eye exams if the cause is diabetes
- Using blue light blockers or other devices to reduce visual snow if the cause is visual snow syndrome
- There is no specific treatment for RP, but some therapies such as gene therapy, stem cell therapy, or retinal implants are being researched2
Diagnosis of nyctalopia
The diagnosis of nyctalopia involves evaluating your medical history and performing a standard eye examination. Your eye doctor may also order some blood tests to check your levels of vitamin A and glucose, which can affect your night vision. Additionally, your eye doctor may order some specialized tests to assess the function of your retina and optic nerve. These tests may include:
- Electroretinography (ERG): measures the electrical activity of the retina in response to light stimuli
- Visual field testing: measures your peripheral vision and detects any blind spots or scotomas
- Optical coherence tomography (OCT): uses light waves to create detailed images of the retina and its layers
- Fundus photography: captures images of the back of your eye, including the retina, optic disc, and blood vessels3
Some of the risk factors related to nyctalopia are:
- Age: Older people are more likely to develop eye problems (e.g., cataracts, RP) that can cause night blindness
- Genetics: Some eye diseases that cause nyctalopia are inherited, such as RP or choroideremia
- Diet: A lack of vitamin A or other nutrients that are essential for eye health can lead to nyctalopia. Vitamin A deficiency is more common in people who have undergone intestinal bypass surgery or follow restrictive or vegan diets.
- Diabetes: High blood sugar levels can damage the blood vessels and nerves in the retina, leading to diabetic retinopathy, which can impair night vision
- Medications: Some drugs that affect the pupil size or the retina can cause nyctalopia, such as glaucoma medications, phenothiazines, and chloroquine1
Nyctalopia can lead to several complications, which include the following:
- Reduced quality of life: People with nyctalopia may have difficulty performing daily activities at night or in dim light, such as driving, reading, or walking. They may also avoid going outside at night for fear of tripping or getting into accidents.
- Progressive vision loss: Some eye diseases that cause nyctalopia, such as RP and glaucoma, can lead to permanent damage to the retina and optic nerve, resulting in gradual loss of peripheral vision and, eventually, central vision.
Nyctalopia can also be a sign of other eye problems that may require treatment, such as cataracts, diabetic retinopathy, or vitamin A deficiency. If left untreated, these conditions can cause further complications such as blindness, infection, or inflammation.1
Can nyctalopia be prevented?
Nyctalopia can be prevented by addressing the underlying cause of the condition. Some possible ways to prevent nyctalopia are:
- Maintaining good eye health: Having regular eye exams can help detect and treat eye problems that can cause nyctalopia, such as cataracts, glaucoma, or RP.2,3
- Eating a balanced diet: Consuming foods that are rich in vitamin A and other nutrients that support eye health can help prevent nyctalopia caused by vitamin A deficiency. Some sources of vitamin A are liver, eggs, dairy products, carrots, spinach, and sweet potatoes.
- Managing blood sugar levels: Keeping blood sugar levels under control can help prevent or delay diabetic retinopathy, a complication of diabetes that can damage the retina and cause nyctalopia.
- Avoid certain medications: Some drugs that affect the pupil size or the retina can cause nyctalopia as a side effect. These include glaucoma medications, phenothiazines, and chloroquine. If you are taking any of these medications, consult your doctor about the risks and benefits.4
How common is nyctalopia?
The prevalence of nyctalopia varies depending on the cause and the population. Some estimates are:
- Retinitis pigmentosa: This is the most common cause of nyctalopia and affects about 1 in 4,000 people worldwide.
- Cataract: This is a common eye problem that affects about half of the people over 65 years old and can cause nyctalopia if it affects the peripheral part of the lens.³
- Vitamin A deficiency: This is a rare cause of nyctalopia in developed countries but is more common in developing countries where malnutrition is prevalent. It affects about 250,000 to 500,000 children every year, mainly in Africa and Southeast Asia.⁴
- Diabetes: This is a common condition that affects about 10% of adults worldwide and can cause nyctalopia due to diabetic retinopathy, which damages the retina.⁴
Is nyctalopia genetic?
Symptoms of several eye diseases can be genetic. For example, retinitis pigmentosa is a genetic disorder that causes the rod cells in the retina to gradually lose their ability to respond to light, leading to progressive nyctalopia and eventual vision loss.² Another genetic condition that causes nyctalopia is congenital stationary night blindness (CSNB), which affects the transmission of signals from the photoreceptors to the bipolar cells in the retina.5
When should I see a doctor?
You should see a doctor if you notice difficulty seeing in dim light or at night. You should see a doctor immediately if you notice sudden changes in vision, especially when you do not know the cause. The specialist for nyctalopia is a primary care physician who can diagnose and treat the underlying eye problem.1
Nyctalopia is a condition that makes it difficult to see in low light. It is not a disease by itself but rather a sign of an underlying eye problem, usually related to the retina. It can be caused by various factors, such as nearsightedness, cataracts, retinitis pigmentosa, vitamin A deficiency, diabetes, glaucoma, or certain medications. Nyctalopia can affect the quality of life and safety of people who have it, especially when driving or working at night. Treatment for nyctalopia depends on the cause and may include glasses, medication, surgery, or dietary supplements. Nyctalopia can be prevented by eating foods rich in vitamin A and having regular eye exams.
- Cleveland Clinic [Internet]. [cited 2023 Nov 4]. Night blindness (Nyctalopia): definition, causes & symptoms. Available from: https://my.clevelandclinic.org/health/symptoms/10118-night-blindness-nyctalopia
- Traber GL, Piccirelli M, Michels L. Visual snow syndrome: a review on diagnosis, pathophysiology, and treatment. Curr Opin Neurol. 2020 Feb;33(1):74–8.
- Mehra D, Le PH. Physiology, night vision. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Nov 4]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK545246/
- Rao VR, Cohen GB, Oprian DD. Rhodopsin mutation G90D and a molecular mechanism for congenital night blindness. Nature [Internet]. 1994 Feb [cited 2023 May 26];367(6464):639–42. Available from: https://www.nature.com/articles/367639a0
- Nyctalopia - an overview | sciencedirect topics [Internet]. [cited 2023 May 26]. Available from: https://www.sciencedirect.com/topics/medicine-and-dentistry/nyctalopia