Nictalopia: Definition, Symptoms, Causes, Diagnosis, Treatment, Prevention and Outlook

Do you have difficulty seeing at night?

The night blindness is common among older drivers, but the problems seeing at night can also be caused by a number of eye conditions that affect people of all ages.

Nictalopia (/ ˌnɪktəloʊpiə / from Greek νύκτ- (nykt-), which means “night”, ἀλαός (alaos), which means “blind, not seeing”, and ὄψ (ops), which means “eye”), also called blindness night, it is a condition that makes it difficult or impossible to see in relatively low light.

Despite the name “night blindness,” the condition does not mean that someone becomes completely blind at night. In contrast, a person with night blindness may have difficulty distinguishing between objects at night or seeing halos around lights at night.

It can be described as insufficient adaptation to darkness. To identify the cause, your ophthalmologist will perform a complete exam. He can order specialized tests.

Not only do people with night blindness see poorly at night, but they also require additional time for their eyes to adjust from well-lit to dimly-lit areas. Contrast vision can also be greatly reduced.

The rods contain a receptor protein called rhodopsin. When light falls on rhodopsin, it undergoes a series of conformational changes that ultimately generate electrical signals that are transmitted to the brain through the optic nerve.

In the absence of light, rhodopsin regenerates. The body synthesizes rhodopsin from vitamin A, so a deficiency in vitamin A causes poor night vision.

Refractive vision correction surgery (especially photorefractive keratectomy (PRK) with the complication of “haze”) can rarely cause a reduction in nocturnal acuity.

How the eye works in the dark

Light travels through the cornea and lens and lands on the retina at the back of the eye. The retina is made up of photoreceptors, specialized nerve cells that convert light rays into electrical signals and transmit them to the brain, which then creates an image.

There are two types of photoreceptors, rods and cones. There are about 3 million cones and 100 million rods in each eye.

The rods only see black and white, but the cones see the colors. The rods also allow the eyes to detect movement and provide peripheral vision.

The rods are responsible for vision in low light and the cones are responsible for vision in bright light. The rods extend throughout the retina, but the cones are only in the center of the retina.

Vision in twilight or darkness is blurred due to connections between photoreceptors and nerve cells that are linked to the brain.

Each rod must share this connection with other rods so that the brain does not know exactly which rod produced the signal.

Bright light vision is sharp because each cone has its own connection to the brain, so the brain can determine exactly where on the retina the signal originated.

Another characteristic of the bars is that they must adapt to the dark. This is best exemplified by walking into a dark theater. At first one can see very little. Over time, vision improves and one can discern objects.

In short, one can see moderately well. This dark adaptation process occurs due to the chemical nature of rhodopsin. Rhodopsin breaks down in bright light, causing the rods to not work.

In the dark, rhodopsin regenerates faster than it can break down. Complete dark adaptation takes about 15-30 minutes, and when complete, light sensitivity increases about 100,000 times.

Night blindness is most dangerous when someone who has trouble seeing in the dark gets behind the wheel of a car.

People who experience night blindness should not drive at night or at night.

Oncoming car headlights and street lamps can make it especially difficult to see clearly and drive safely.

Nictalopia and hemeralopia

Nyctalopia and hemeralopia are the rare examples of words that can lead to a fair amount of controversy and confusion among doctors of different linguistic backgrounds, due to different definitions and meanings.

Nictalopia : is a word from ancient Greek medicine, defined as “night blindness” or defective dark adaptation.

Hemeralopia : is a word that originated in the 18th century, which means “day blindness” or visual defect characterized by the inability to see as clearly in bright light as in dim light.

Standard English dictionaries also conform to the meanings of nyctalopia and hemeralopia as night blindness and day blindness, respectively. However, the words have been used in the opposite sense by many non-English speaking physicians.

To reduce confusion, it is recommended to use correctly understandable terms such as night blindness and day blindness.

There was a decreasing trend in the use of the word hemeralopia and an increasing trend in the use of nyctalopia to describe night blindness.

The results confirm that the word hemeralopia, but not nyctalopia, has been used incorrectly in the literature among non-English speaking countries.

However, currently, there is an improved trend of compliance with the recommendation that correctly understandable words such as night blindness and day blindness be used instead of the controversial nyctalopia and hemeralopia, respectively.

Symptoms of nyctalopia

People with night blindness experience poor vision at night or in low light environments.

Although the term “night blindness” implies that you cannot see at night, this is not the case. You may have more trouble seeing or driving in the dark.

You are more likely to experience night blindness when your vision changes from a bright setting to a dimly lit area, such as when you step off a sunny sidewalk into a dimly lit restaurant.

You are likely to experience poor vision while driving due to intermittent glare from headlights and street lights on the road.

Night blindness is a symptom of several different diseases or conditions, sometimes caused by unlikely illnesses or medications.

All possible causes of night blindness are associated with the way the eye receives light rays.

Causes of nyctalopia

Once you know the cause of the problem, you can take steps to correct your vision. The problem stems from a disorder of the cells in the retina that allows you to see dim light.

Patients suffering from this genetic condition have progressive nyctalopia, and eventually their daytime vision can be affected as well. It has many causes:

  • Retinitis pigmentosa.
  • Retinal detachment.
  • Certain medications, such as phenothiazines.
  • Oguchi disease.
  • Pathological myopia.
  • Cataract (peripheral cortical).
  • Refractive surgery (LASIK (laser-assisted in situ keratomileusis), photorefractive keratectomy, radial keratotomy).
  • Background Sorsby’s dystrophy (macular degeneration).
  • Vitamin A deficiency.
  • Choroideremia.
  • Glaucoma.

Patients who have pancreatic insufficiency, such as people with cystic fibrosis, have difficulty absorbing fat and are at increased risk for vitamin A deficiency because vitamin A is fat soluble.

This puts them at higher risk of developing night blindness. Therefore, older people are more likely to have night blindness due to cataracts than children or young adults.

There are several eye conditions, vitamin deficiencies, and chronic diseases that can affect your night vision and your ability to see while driving at night, including:

Age : As we age, our pupils do not dilate in the dark as much as they should, thus reducing the amount of light that enters our eyes.

Corneas also become less clear with age, increasing the amount of glare you can see and reducing contrast sensitivity, which can make it difficult to distinguish between objects at night.

Presbyopia : Presbyopia develops with age and can make it difficult to focus and adjust to changes in light. It can also make driving at night or in the rain more challenging for older adults.

Glaucoma : Glaucoma is a build-up of pressure in the eye that can affect peripheral vision. Without peripheral vision, it is difficult to see what is going on around you, which is especially dangerous while driving.

Cataracts : Cataracts are a clouding of the lens of the eye, which confuses the field of vision and makes it difficult to see objects clearly.

Cataracts can further inhibit night driving vision, as many with cataracts describe great difficulty with glare and halos from oncoming headlights.

Diabetic retinopathy – a condition in the back of the eye caused by diabetes. Diabetic retinopathy can cause significant vision loss and is the leading cause of retinal blindness in adults ages 20 to 64.

Retinitis pigmentosa : A rare genetic disorder in which dark pigment accumulates in the retina, creating tunnel vision.

This condition generally affects people under the age of 30. Worsening night vision is one of its first symptoms.

Nutritional deficiency : A deficiency of vitamin A and zinc can also contribute to night blindness.

Although rare, not getting enough vitamin A in your diet could affect your night vision. Zinc helps the body absorb vitamin A, so without zinc, vitamin A is not as effective.

Sun Exposure – Without proper eye protection, sun exposure can temporarily impair night vision for up to two days.

Wearing sunglasses that protect against ultraviolet A (UVA) and ultraviolet B (UVB) rays will prevent temporary night blindness due to sun exposure.

Complications After Eye Surgery : Laser-assisted in situ keratomileusis (LASIK) eye surgery, although uncommon, a patient who underwent LASIK eye surgery may experience distorted night vision after surgery.

The most common complaint is seeing flare or halos around lights at night.

Historical use

Aulus Cornelius Celsus , described night blindness and recommended an effective dietary supplement:

“In addition to the weakness of the eyes, because people see enough during the day, but not at night, in women whose menstruation is regular this does not”.

“But those who are successful must anoint their eyes with things dripping from a liver while roasting, preferably from a goat or failing that of a goat, and they must also eat part of the liver.”

Historically, nyctalopia, also known as moonblink, was a temporary night blindness believed to be caused by sleeping under moonlight in the tropics.

In the French language, nyctalopie and héméralopie have reverse meanings, the former mentioning the ability to see both in the dark and in full light, and the latter the inability to do so.

This inversion of the Latin is thought to have occurred during the 2nd century AD, although the ancient Greek νυκτάλωψ (nuktálōps) has been used in both senses.

Night blindness, sometimes known as gravel, was occasionally documented during the American Civil War, particularly within the Confederate States of America.

Like rheumatism, night blindness was seen as a condition that could be easily faked or exaggerated, and patients initially viewed each other with some mistrust.

Some soldiers who reported symptoms of nyctalopia also had symptoms of scurvy, suggesting a root cause of poor nutrition.

Nictalopia in animals

Congenital stationary night blindness (CSNB) is usually diagnosed based on the owner’s observations, but some horses have visibly abnormal eyes:

Misaligned eyes (dorsomedial strabismus) or involuntary eye movement (nystagmus).

In horses, congenital stationary night blindness has been linked to the complex leopard color pattern since the 1970s.

A 2008 study theorizes that both congenital stationary night blindness and complex leopard spotting patterns are related to the TRPM1 gene.

The region of horse chromosome 1 in which the Lp gene has now been located also encodes a protein that channels calcium ions, a key factor in the transmission of nerve impulses.

This protein, found in the retina and skin, exists in fractional percentages of the normal levels found in homozygous Lp / Lp horses and compromises the basic chemical reaction for nerve impulse transmission.

Diagnosis of nyctalopia

To determine what is causing your night blindness, an eye doctor will perform a comprehensive eye exam and may order any of a number of specialized exams.

Night blindness can be diagnosed and treated by an ophthalmologist, a doctor who specializes in eye disorders. Opticians can only dispense glasses, but optometrists can diagnose and treat vision problems.

Diagnosis begins with a detailed medical history of night blindness. Questions include:

  • Severity of night blindness, when the night blindness started, and whether it occurred gradually or suddenly.

An eye exam is done, and a slit lamp scan, in which a narrow beam of intense light is used to examine the internal components of the eye, may also be done.

Additional tests can be performed based on the results of these standard tests.

Differential for night blindness

  • Albinism.
  • Waterfalls.
  • Glaucoma.
  • Atrofia de Gyrate.
  • Oguchi disease.
  • Optic atrophy.
  • Retinitis pigmentosa.
  • Siderosis.
  • Uncorrected myopia.
  • Vitamin A deficiency.
  • Zinc deficiency.

Seek medical attention if …

Vision changes should never be taken lightly. Because night blindness can be a symptom of a serious illness, an ophthalmologist should be consulted before a person begins self-treatment.

If you have trouble distinguishing between objects at night or if you see halos around lights in the dark, tell your doctor. These can be early symptoms of a more serious eye condition, and early diagnosis can save your vision.

How is night blindness treated?

Your eye doctor will take a detailed medical history and examine your eyes to diagnose night blindness. You may also need to give a blood sample.

Treatment for night blindness will depend on its cause. Treatment can be as simple as getting a new eyeglass prescription or changing glaucoma medications, or it may require surgery if night blindness is caused by cataracts.

If retinal disease is discovered, treatment will depend on the type of disease and will require further investigation by a retina specialist.

Tell your doctor if you still have trouble seeing in low light even with corrective lenses.


The dark parts of the lens of your eye are known as cataracts. If cataracts are the cause of your night vision problems, cataracts can be removed by surgery, it should help improve your overall vision, including night vision.

Your surgeon will replace your cloudy lens with a clear, artificial lens. Your night blindness will improve significantly after surgery if cataracts are the underlying cause.

Vitamin A deficiency

If your vitamin A levels are low, your doctor may recommend vitamin supplements. Take the supplements exactly as directed.

Genetic defect

Genetic conditions that cause night blindness, such as retinitis pigmentosa, are not treatable.

Diabetic retinopathy

If diabetic retinopathy is the cause of your night blindness, controlling your blood sugar through medications and diet can help prevent vision loss.

How can I prevent night blindness?

You cannot prevent night blindness that is the result of birth defects or genetic conditions, such as Usher syndrome.

However, you can properly control your blood sugar levels and eat a balanced diet to decrease your chance of night blindness.

Eat foods rich in antioxidant vitamins and minerals, which can help prevent cataracts.

Also, choose foods that contain high levels of vitamin A to reduce the risk of night blindness. Certain orange foods are excellent sources of vitamin A, including:

  • Cantalupos.
  • Sweet potatoes.
  • Carrots
  • Pumpkins.
  • Pumpkin.
  • Mangos.

Vitamin A is also in:

  • Spinach.
  • Kale.
  • Milk.
  • Eggs.

What is the long-term outlook?

If you have night blindness, you need to take precautions to protect yourself and others. Avoid driving as much as possible until the cause of your night blindness is determined and, if possible, treat it.

Arrange to drive during the day or secure transportation from a friend, family member, or taxi service if you need to go somewhere at night.

Wearing sunglasses or a fedora can help reduce glare when in a well-lit environment, which can ease the transition to a darker environment.