What Is Nyctalopia (Night Blindness)?

Nyctalopia, also known as night blindness, reduces a person’s ability to see clearly at night or in environments with low lighting. Daytime vision is unimpaired even when someone has nyctalopia. Nyctalopia is not a disease itself but a symptom of an underlying problem, In some cases, myopia can make it very hard to see at night.

In a dark environment, your pupils dilate to let more light into your eyes. This light is received by the retina, which houses the cells that help people see colors (cone cells) and in the dark (rod cells). When there is a problem with the rod cells because of a disease or injury, you can’t see well or at all in the dark, resulting in night blindness.

Nyctalopia Symptoms

Nyctalopia is itself a symptom. You may notice if you have night blindness in certain circumstances, including:

• Having trouble moving around your house at night, even with small night lights
• Driving at night is more difficult
• Avoiding going outside at night for fear of tripping
• Having trouble recognizing people’s faces in darkened settings like movie theaters
• Taking a long time for your eyes to adjust to light when coming inside from the darkness
• Taking a long time to adjust to seeing in a darkened room

If you are worried about not being able to see in the dark or suspect you have night blindness, have your eyes checked by an eye care professional.

Causes

Night blindness can be a symptom of several diseases, including:

• Retinitis pigmentosa: is one of a group of rare, genetic diseases (also including choroideremia) affecting the retina that can result from a change in any one of 100 genes. It can cause progressive vision loss. The rod cells in the retina are more severely affected in the early stages of these diseases, and one of the first symptoms is night blindness.
• Cataracts: More than half of all Americans aged 80 or older either have cataracts or have had surgery to get rid of cataracts. Cataracts happen when there is clouding of the eye’s lens, and can cause night blindness. Trouble seeing at night is usually one of the first symptoms.
• Glaucoma: This condition occurs when fluid builds up in the front part of the eye and increases the pressure on the eye, damaging the optic nerve. Glaucoma first attacks peripheral vision before harming central vision. Both daytime and nighttime vision are affected as parts of the retina stop working.
• Myopia: When the eyeballs are too long normal or the cornea is steeper than average, people will develop myopia, also known as nearsightedness. This condition impairs the ability to see objects that are far away during the day and at night. Some people may experience blurred distance vision only at night. With night myopia, low light makes it difficult for the eyes to focus properly, or the increased pupil size during dark conditions allows more peripheral, unfocused light rays to enter the eye.
• Vitamin A deficiency: To see the full spectrum of light, your eye needs to produce certain pigments for your retina to work properly. Vitamin A deficiency stops the production of these pigments, leading to night blindness. 
• Diabetes: High sugar levels in the blood can harm the blood vessels in the retina, causing vision problems like diabetic retinopathy. Nyctalopia is often one of the first symptoms of diabetic retinopathy.
• Some glaucoma medications: Some miotics medication used to treat glaucoma can make the pupil smaller and cause nyctalopia.
• Keratoconus: This condition occurs when when the cornea thins out and bulges like a cone. Changing the shape of the cornea brings light rays out of focus. Night blindness is a symptom of keratoconus.
• Astigmatism: vision problem caused by an irregularly shaped cornea that prevents light from focusing properly on the retina, the light-sensitive surface at the back of the eye. The most common symptom is blurred or distorted vision at any distance.

Diagnosis

Diagnosis depends on what’s causing the night blindness. The ophthalmologist or optometrist will ask about your symptoms, family history, and medications and perform an eye exam to identify the cause of your night blindness. If necessary, the specialist will request additional tests, such as a blood sample, to measure glucose and vitamin A levels.

Treatment

The treatment will also depend on the underlying condition causing night blindness:

• Retinitis pigmentosa:  People with retinitis pigmentosa need vision rehabilitation and also genetic testing to see if any future or current possible treatments exist for them.
• Cataracts: Surgery is the only way to remove cataracts. When it doesn’t affect daily activities, people can cope with the disease by wearing eyeglasses.
• Glaucoma: Eye drops can be used to reduce the amount of fluid the eye makes and therefore lower eye pressure. Laser surgery to help with fluid outflow from the affected eye is another option.
• Myopia: The most common ways to treat nearsightedness is by wearing eyeglasses, contact lenses, or refractive surgery like LASIK. Other options include multiple hard lenses to flatten the cornea (orthokeratology) or low-dose atropine (0.01%) to slow the progression of myopia in children and adolescents.
• Vitamin A deficiency: Oral vitamin A supplements can solve the problem, and the healthcare providers will establish the amount necessary for each case. Eating vitamin A-rich foods, such as liver, beef, chicken, eggs, fortified milk, carrots, mangoes, sweet potatoes, and leafy green vegetables, can also help increase your intake of vitamin A.
• Diabetes: The treatment will focus on controlling sugar levels, and depends on the type of diabetes you have. It can involve lifestyle changes, regular blood sugar monitoring, insulin, and medication.
• Keratoconus: Mild symptoms can be managed with eyeglasses and later special hard contact lenses. Other treatment options include intacs (small devices that can flatten the curvature of the cornea), collagen cross-linking (uses a special UV light and eye drops to strengthen the cornea), and corneal transplant for severe cases.

Prognosis

Night blindness is treatable when it’s caused by certain things, like myopia, vitamin A deficiency, and cataracts. But other causes of night blindness like retinitis pigmentosa or other inherited retinal diseases have no cure, so your healthcare provider may discuss options that improve your quality of life and lessen symptoms.

A Word From Verywell

It is essential to schedule a visit with your healthcare provider when you notice night blindness or other changes in your vision. As the symptom can be linked to many conditions, getting an eye exam is important for identifying the underlying cause. 

Research on treatment for these conditions is ongoing. Your healthcare provider can advise you on assistive technologies and vision rehabilitation that may be appropriate for you.