Night blindness | definition of night blindness by Medical dictionary Night blindness | definition of night blindness by Medical dictionary night blindness inability or a reduced ability to see in dim light; the eyes not only see more poorly in dim light, but are slower to adjust from brightness to dimness. Called also nyctalopia . Depending on its brightness, light is perceived by either of two sets of visual cells located in the retina of the eye. One set, the cones, perceive bright light primarily; the other set, the rods, perceive dim light primarily. Dim light produces a change in a pigment called rhodopsin in the rods. This change causes nerve impulses to travel to the brain, where they register as visual impressions. Night blindness occurs when the rods lack rhodopsin. One cause of night blindness is a deficiency of vitamin A—the primary source of rhodopsin. The defect in vision usually can be cured by proper diet plus therapeutic doses of the deficient vitamin. In the elderly, there is sometimes a diminution of rhodopsin, with resulting night blindness. Other losses in vision may follow. Diminished blood supply to the eyes is thought to be a cause of this form of the condition. Treatment generally is only of limited effectiveness.

Night blindness sometimes accompanies glaucoma. nyc·ta·lo·pi·a (nik-tă-lō'pē-ă), Decreased ability to see in reduced illumination. Seen in patients with impaired rod function; often associated with a deficiency of vitamin A. 2. Retinitis pigmentosa , see there. 3. Nyctalopia Defective vision in ↓ illumination, often implying defective rod function with delayed dark adaptation and perceptual threshold; it is either congenital and stationary with myopia and degeneration of the disc–eg, retinitis pigmentosa, hereditary optic atrophy or progressive and acquired with retinal, choroidal or vitrioretinal degeneration–eg, cataract, glaucoma, optic atrophy, retinal degeneration and, the 'classic' cause of nyctalopia, vitamin A deficiency. nyc·ta·lo·pi·a (nik'tă-lō'pē-ă) Decreased ability to see in reduced illumination. Seen in patients with impaired rod function; often associated with a deficiency of vitamin A. [nyct- + G. alaos, obscure, + ōps, eye] blindness (blind'nes) Inability to see.

The leading causes of blindness in the U.S. are age-related macular degeneration, diabetic retinopathy, and glaucoma. Blindness may be caused by diseases of the lens, retina, or other eye structures; diseases of the optic nerve; or lesions of the visual cortex or pathways of the brain. A small number of infants are born blind, but far more people become blind during life. In the U.S., blindness due to infection is rare, but worldwide diseases like trachoma and onchocerciasis are relatively common causes of severe visual impairment. In malnourished people, vitamin A deficiency is an important cause of blindness. A variety of free services are available for the blind and physically handicapped. Talking Books Topics, published bimonthly in large-print, cassette, and disc formats, is distributed free to the blind and physically handicapped who participate in the Library of Congress free reading program. It lists recorded books and magazines available through a national network of cooperating libraries and provides news of developments and activities in library services. Subscription requests may be sent to Talking Books Topics, CMLS, P.O. Box 9150, Melbourne, FL 32902-9150.

amnesic color blindness Alexia. night blindness Moderately reduced to severely defective vision in dim light. Night blindness (nyctalopia) occurs in many people with no objectively discernible eye disorder, but is common in short-sighted people, in those with vitamin A deficiency and in the early stages of degenerative diseases of the RETINA including RETINITIS PIGMENTOSA . night blindness see VITAMIN A . hemeralopia Term used to mean either night blindness in which there is a partial or total inability to see in the dark associated with a loss of rod function or vitamin A deficiency; or day blindness in which there is reduced vision in daylight while vision is normal in the dark. Syn. nyctalopia (this term is only synonymous with night blindness); night sight (this term is only synonymous with day blindness). See girate atrophy; congenital stationary night blindness ; choroideremia ; Oguchi's disease ; retinitis pigmentosa . night blindness inability or a reduced ability to see in dim light. In night blindness, the eyes not only see more poorly in dim light, but are slower to adjust from brightness to dimness. It is a sign of hypovitaminosis A and early progressive retinal atrophy.

Testing for night blindness entails construction of an obstacle race and putting an animal through it at dusk. Difficult to interpret results. congenital night blindness occurs in Appaloosa horses. There is a retinal defect which is detectable by electroretinography. Vision - night blindness: MedlinePlus Medical Encyclopedia Retinitis pigmentosa Home Care Take safety measures to prevent accidents in areas of low light. Avoid driving a car at night, unless you get your eye doctor's approval. Vitamin A supplements may be helpful if you have a vitamin A deficiency. Ask your health care provider. When to Contact a Medical Professional It is important to have a complete eye exam to determine the cause, which may be treatable. Call your eye doctor if symptoms of night blindness persist or significantly affect your life. What to Expect at Your Office Visit Your provider will examine you and your eyes. The goal of the medical exam is to determine if the problem can be corrected (for example, with new glasses or cataract removal ), or if the problem is due to something that is not treatable. The doctor may ask you questions, including: How severe is the night blindness? When did your symptoms start? Did it occur suddenly or gradually? Does it happen all the time?

Does using corrective lenses improve night vision? Have you ever had eye surgery? What medications do you use? How is your diet? Have you recently injured your eyes or head? Do you have a family history of diabetes ? Do you have other vision changes? What other symptoms do you have? Do you have unusual stress, anxiety, or a fear of the dark? The eye exam will include: Color vision testing External and internal eye anatomy References Sieving PA, Caruso RC. Retinitis pigmentosa and related disorders. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, MO: Elsevier Mosby; 2008:chap 6.10. Tomsak RL. Vision loss. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, PA: Butterworth-Heinemann; 2008:chap 14. Tsang SH, Gouras P. Molecular Physiology and Pathology of the Retina. In: Tansman W, Jaeger EA, eds. Duane's Ophthalmology.

2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:chap 2. Review Date 9/2/2014 Updated by: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team. Related MedlinePlus Health Topics Night blindness - Medical dictionary Night blindness The inability to see well in dim light. Many people with night blindness have no discernible eye disease. The condition may be an inherited functional defect of the retina, an early sign of retinitis pigmentosa , or a result of vitamin A deficiency. Night Blindness - OurMed Night Blindness Rating: 0.0/5 (0 votes cast) login to rate Night blindness is defined as vision that is defective in reduced light. It can be caused by genetic disease, certain drugs, or vitamin A deficiency. Night blindness can be mild and merely an inconvenience, or it can be severe and limiting, especially in certain occupations such as piloting an airplane or in the military.

Contents 11 References Terminology The medical term for night blindness is nyctalopia. This is in contrast to hemeralopia, which is the inability to see in bright light. a = optic nerve:b = optic disc:c = sclera:d = choroid:e = retina:f = zonular fibres:g = posterior chamber:h = iris:i = pupil:j = cornea:k = anterior chamber (filled with aqueous humour):l = ciliary muscle:m = lens:n = suspensory ligament:o = vitreous humour:p = fovea. Source: Wikimedia Commons Night Vision The eye sees using the retina of the eye . The retina is a net of nerve cells located at the back of each eye that enable vision. The retina is made up of two main kinds of cells: rods and cones. Cones are responsible for color vision and work best in bright light. Rods work in low light but are unable to see color. The cones are located mainly in the center of the retina, while the rods are located around the edges. This is why our vision at night is less colorful. This is also why we can see better in very dim light when we look slightly away from what we are looking at.

In complete darkness (an absolute absence of light), neither the cones nor the rods can function, and we would see absolutely nothing. However, in dim light, we can see amazingly well, mainly because of the rods in our retina. A rod can register a single photon of light. This means that a human with perfect vision can see a lit match several miles away on a clear night. Symptoms Night blindness is generally caused by impaired functioning of the rods. This can result in a longer time to adapt to light and in a higher threshold of light needed to see at all. People with night blindness see poorly at night, and they also require more time for their eyes to adjust from bright areas to dim ones. In addition, people with night blindness may have poor contrast vision, especially in low light situations. Causes The causes of night blindness can be categorized as genetic or acquired, stationary (not changing) or progressive. Genetic causes Congenital stationary night blindness is a general term referring to a genetic condition of night blindness that arises from birth. It does not get better or worse over time. It is due to an inherited genetic defect that affects the retina.

It is sometimes associated with myopia (short-sightedness) and nystagmus (an involuntary tremor of the pupil of the eye). The genetic basis of congenital stationary night blindness is either X-linked , autosomal recessive, or autosomal dominant. X-linked congenital stationary night blindness is passed from mother to son on the X chromosome . For a woman to be affected, she must have an affected father and a mother who is a carrier of the gene . The condition comes in two forms--complete and incomplete. The complete form is characterized by a complete absence of function of the rod cells. Each of the two forms is caused by a separate genetic defect of the X chromosome. X-linked congenital stationary night blindness is also associated with myopia, nystagmus, and strabismus (a deviation of the eye, otherwise known as squint or cockeye). Oguchi disease is the autosomal recessive form of congenital stationary night blindness. It is associated with a yellow or gray discoloration of the fundus (the back of the eye, where the retina is located). People suffering from Oguchi disease adapt very slowly to darkness.

After two to three hours in total darkness, the normal color of the fundus returns, and the individual slowly adapts to night vision. This disease is more common in individuals of Japanese ethnicity. Retinitis pigmentosa is the most common genetic cause of night blindness. Retinitis pigmentosa is a neurocutaneous syndrome, a genetic condition affecting the skin and the nerves of the eye (the retina). The first sign of this disease is a loss of night vision in early childhood. After that, there is a slow, progressive loss of peripheral vision, until only tunnel vision remains. This eventually leads to total blindness, which usually does not set in until the 40's or 50's. However, the progression varies. Some people never lose their sight, and some people become blind early in childhood. Another sign of this disease is a change in the pigmentation of the skin of the lower abdomen, which also occurs in early childhood. There is no definitive cure for this disease, but high doses of vitamin A can slow its progression, and may delay the onset of blindness by ten years. Future treatments may include retinal transplant, artificial retinal implants, and stem-cell treatment of the genetic defect.

Acquired Causes Most of the acquired causes of night blindness (night blindness which is not present since birth and does not have a genetic basis), generally fall into the category of progressive night blindness. This condition is usually caused by progressive degeneration of the retina. The most common acquired cause of night blindness is vitamin A deficiency. Vitamin A deficiency is rarely discovered, diagnosed, and treated, and so it is considered rare in developed countries. However, milder forms of this condition may be vastly underreported and underdiagnosed, as people generally make do without ideal night vision, or may not need good night vision. Dependence on night vision varies among individual habits and work conditions. As such, vitamin A deficiency may be the most common cause of night blindness. The retina requires vitamin A for many reasons. Vitamin A forms a much needed nutrient for the nerve cells of the retina. Vitamin A is needed in significant amounts for light detection. In this respect, it is a component of the protein rhodopsin, which switches between the "off" and "on" positions in the presence of light. Vitamin A is needed to turn rhodopsin back to the off configuration.

Without adequate vitamin A, the function of the rod cells deteriorate, and night blindness sets in. Vitamin A is fat-soluble, and as a result it is stored by the body. A deficiency results only after months of foregoing any food with vitamin A. As such, it does not occur often. It may occur in settings with a very restricted availability of food, such as in some settings in the military or in developing countries. Children are susceptible to a deficiency either because they may not have built up large reserves, or because they are excessively picky in their diet. Pregnant women are also more susceptible to night blindness, especially during the seventh month of pregnancy when the demand for vitamin A by the fetus increases. Approximately 127 million preschool-aged children and 7 million pregnant women are deficient in vitamin A, and 6 million pregnant mothers worldwide have night blindness. [1] Diseases or conditions that result in poor absorption of fat will result in a deficiency of fat-soluble vitamins, including vitamin A, and can lead to night blindness. As such, night blindness may be associated with cystic fibrosis and Crohn's disease . Drugs are another cause of night blindness.

Drugs that can damage the retina and cause night blindness are called retinotoxic. Use of Quinine is often associated with night blindness. isotretinoin ( Accutane ) also has been associated with night blindness, particularly in people who have a low level of vitamin A before starting the medication. Since the rods of the retina are located mainly on the outer edges of the retina, any condition that causes degeneration or damage to the outer edges of the retina may cause night blindness. For example, Peripheral Cortical Cataract can be associated with night blindness. Cataracts , chronic glaucoma , and choroidal dystrophy are other such conditions. Impact Night blindness has likely caused numerous automobile accidents, although this has been difficult to document. Most accidents occur around sunset, and this may be due to poor contrast vision as well as poor night vision. Generally, even at night in most places, headlights and streetlights provide enough light to see. However, this is not always the case in rural areas. Someone with documented night blindness may be restricted from driving at night. Night vision is especially important for pilots, both commercial and in the military where vision is routinely checked. Night blindness can be disqualifying in these jobs.

A military occupation that particularly relies on night vision is the scout. Although soldiers in most positions in the military depend on night vision, the scout specializes in having good night vision. Night blindness, even if temporary, during times of war can prove to be dangerous or fatal. Some children who are afraid of the dark may in fact have night blindness. Fear of the dark, or nyctophobia, in children is not a fear of the dark per se but a fear of partially visible things in the room heightened by imagination. Night blindness may add to this effect, as the child may not be able to clearly see objects in the room for what they are. Diagnosis Diagnosis of night blindness in adults can be straightforward. A drug history and a diet history may be all that is needed to determine the cause. A trial of treatment with vitamin A may help as well. Occasionally, night blindness thought to be caused by vitamin A deficiency may actually be due to an underlying malabsorption disorder of the intestines and an inability to absorb fat-soluble vitamins. In children, the diagnosis is difficult or impossible. It is possible that there are many children who have temporary night blindness due to vitamin A deficiency but go undiagnosed.

As mentioned above, a new-onset fear of the dark may be a clue. Another clue is increased falls and bumps at night after the lights are out. Testing Testing can be done in a clinic or office. It is important to remember that a small amount of dim light is needed in order to see at all. Turning off the lights and holding a few fingers up is all that is needed to test for night blindness. It is important to test at what level of light the patient can see the object. It is equally important to test the amount of time it takes to see the object. If it is not obvious from the history that the night blindness is due to vitamin A deficiency, ophthalmologist can perform further tests to detect retinal defects and other eye abnormalities. Treatment Treatment of the most common cause of night blindness, vitamin A deficiency, may be as simple as eating a diet rich in vitamin A, or taking supplements. Liver is a very good source of vitamin A because it stores the nutrient. Vitamin A is orange and is generally found in the orange fruits and vegetables (but not in oranges), such as carrots, sweet potatoes, pumpkin, cantaloupe, apricots, papaya, mangoes, and winter squash.

Other good sources are egg yolks and butter. Fortunately, this cause of night blindness is quickly reversible. Genetic causes of night blindness currently have no treatment, although high doses of vitamin A may still delay the progression of night blindness. Future treatments of genetic diseases causing night blindness (and blindness in general) may include retinal transplant, artificial retinal implants, and stem cell treatment of the genetic defect. Trivia Night blindness was also once known as moonblink, which was a temporary night blindness believed to be caused by sleeping in moonlight. Treatment of night blindness with vitamin a was recognized as early as 30 ACE. At that time, the physician Aulus Cornelius Celsus recommended that night blindness be treated with liver, either by applying the fluid extracts of a cooking liver to the eyes, or by consuming the liver itself. Other Resources Night Blindness Symptoms | Reduced Night Vision Renewal Greens 10.6 oz Symptoms Can vary on an individual basis for each patient. Symptoms include weak vision in dim light, difficulty seeing during night driving, and slow vision adaption between bright and dim light conditions. Only your doctor can provide adequate diagnosis of any signs or symptoms and whether they are indeed night blindness symptoms.

Causes & Related Conditions The rods and cones in your eye are the photoreceptors that take in light and pass information through the optic nerve to your brain for interpretation. The rods are responsible for vision in dim light and if there is a problem with these cells, poor or no night vision is the result. Night blindness, known as Congenital night vision disorder (complete or incomplete) is a genetic defect-related condition associated with failure of rods and cones to function correctly. In the complete form the rods in your retina do not respond to light and you cannot see in dim light conditions. But almost any vision condition may result in poor vision which is especially problematic at night, and with sudden shifts from dark to light to dark, as when you are driving at night and another car approaches. If you are having difficulty seeing at night then you should ask your doctor about your symptoms. Retinitis pigmentosa and rod-done dystrophy are specially associated with rod and cone problems.

Other conditions that may result in poor night vision include: celiac disease, cystic fibrosis, bile duct obstruction, cirrhosis of the liver, lasik eye surgery, cataracts, diabetic retinopathy, fuch's dystrophy myopia, glaucoma, macular degeneration, retinal detachment, and vitreous detachment. Diabetes, which develops due to elevated blood sugar levels damages the retina. Night blindness is an early indicator of damage due to diabetes. Cataracts. Early signs of cataracts are poor night vision with halos around lights, glare and blurry vision. Night blindness is also associated with the following nutritional deficiencies. Taurine deficiency Malabsorption - if it affects vitamin A absorption Trace element deficiencies research of night-blinded children aged 3 to 12 found that the children had low levels of zinc, copper and iron and higher-than-normal levels of lead, arsenic, cadmium and sodium.6 Zinc seems especially important as researchers have reported that while zinc alone does not improve night vision, that if the body is deficient in zinc, then the combination of zinc and vitamin A are more effective than vitamin A.1 Diet & Nutrition Vitamin A is the most clearly researched deficiency associated with night blindness.

Certain other nutrients such as bilberry, lutein, ginkgo biloba, taurine, zeaxanthin, and other vitamins and minerals may help night blindness and preserve vision. Zinc if you have a zinc deficiency, then zinc combined with vitamin A is more helpful than vitamin A alone.1 Vegetables. Vitamin A rich vegetables such as dark green vegetables like spinach, collards, and orange and yellow vegetables such as carrots and sweet potatoes. Lifestyle Increase your visibility - clean your headlights Slow down. That way, you give yourself more time to react to any unexpected hazards. Always wear sunglasses outside, especially on bright days. Blue and green eyed people are particularly sensitive to potential sun-induced damage, so the use of eye protection is paramount. Amber and grey lenses are the most effective protection against UVA/UVB and blue light. Get prescription glasses for driving at night if needed (see your eye doctor to determine if they would be helpful). Non-glare glasses. You can get non-glare glasses with a coating that have an anti-reflective coating. Look to the right. Look at the roadway's edge to the right to help you avoid the glare of oncoming headlights. Leave the driving till tomorrow.

Drive only during the day. Even good lighting conditions at night such as found in a big city can be troublesome to someone with night blindness. Nutrient Discussion Vitamin A An early indicator of a deficiency in vitamin A may be night blindness. A primary source of vitamin A is from animal sources, so diets such as a vegan diet without eggs, dairy, some fish, and/or organ meats may result in deficiency of vitamin A. The body makes vitamin A from beta-carotene found in yellow/orange vegetables and fruits, so if those are also not part of the diet, the risk is greater. Health care providers may recommend vitamin A (10,000 - 25,000 IU) daily in order to overcome deficiency. Beta-carotene can also be taken to reverse a deficiency, but it is not as effective as taking vitamin A directly. This is because beta-carotene is absorbed slowly by the body and slowly converted to vitamin A. Vitamin A palmitate is the best form of supplemental vitamin A. 15,000 IU is often the recommended daily dosage (check with your doctor or nutritionist). Note that vitamin A is contra-indicated for those suffering from Stargardt's disease .

Zinc Night blindness may also be the result of a zinc deficiency1 which reduces the activity of an enzyme that helps the body produce vitamin A (retinol dehydrogenase). Research has shown that taking a zinc supplement is helpful. Healthcare providers often recommend 15 - 30 mg of zinc daily for vision. At the same time long-term supplementation with zinc may lower copper levels, so 1 - 2 mg of copper daily is recommended to be taken with zinc for extended use. In general, the recommended supplement ratio is 15:1 zinc to copper. Consult your medical professional for correct dosage if you are supplementing with zinc. Bilberry Bilberry (a blueberry relative) grows in northern Europe and North America in the wild. It is rich in flavonoids, specifically bilberry which is rich in anthocyanosides, the elements in plants that provide color. These natural chemicals are potent antioxidants that, among other benefits, enhance the creation of the purple pigment (rhodopsin) that is used by the rods in the back of the eye to assist with night vision. Early research has shown that bilberry supplementation improves the speed of adapting to darkness for people who have poor night vision.

Taurine Taurine supports the integrity of photoreceptors necessary for night vision2, 3, 7, in a process known as rhodopsin regeneration. Rhodopsin is the primary pigment in photoreceptor rods and so vision in low-light conditions is supported. It also helps to protect cell membranes from free radical damage and helps to remove toxins and debris.4 Taurine is found in the photoreceptors at levels ten times greater than other amino acids.5 Night Blindness News Takes a moment to load ... Footnotes: 2. The role of taurine in osmotic, mechanical, and chemical protection of the retinal rod outer segments, Petrosian AM, Haroutounian JE, Advances in Experimental Medicine & Biology 1998 3. Taurine interactions with chick retinal membranes., Lopez-Colome AM et al, Journal of Neurochemistry, May, 1980 4. American Biologics, Research Institute, Mexico; Tijuana, B.C. Mexico, 1991 5.

Taurine: Biological Update, Wright CE et al, Annual Review of Biochemistry, 1986 Night Blindess: Causes, Symptoms and Treatments Your message has been sent. OK We're sorry, an error occurred. We are unable to collect your feedback at this time. However, your feedback is important to us. Please try again later. Close Night blindness is also called “nyctalopia.” It’s a type of vision impairment. People with night blindness experience poor vision at night or in dimly lit environments. Although the term “night blindness” implies that you can’t see at night, this isn’t the... Read more Night blindness is also called “nyctalopia.” It’s a type of vision impairment. People with night blindness experience poor vision at night or in dimly lit environments. Although the term “night blindness” implies that you can’t see at night, this isn’t the case. You may just have more difficulty seeing or driving in darkness. Some types of night blindness are treatable, and other types aren’t. See your doctor to determine the underlying cause of your vision impairment. Once you know the cause of the problem, you can take steps to correct your vision. What Are the Symptoms of Night Blindness?

The sole symptom of night blindness is difficulty seeing in the dark. You’re more likely to experience night blindness when your eyes transition from a bright environment to an area of low light, such as when you leave a sunny sidewalk to enter a dimly lit restaurant. You’re likely to experience poor vision when driving due to the intermittent brightness of headlights and streetlights on the road. What Causes Night Blindness? A number of eye conditions can cause night blindness, including: nearsightedness, or blurred vision when looking at faraway objects cataracts, or clouding of the eye’s lens retinitis pigmentosa, which occurs when dark pigment collects in your retina and creates tunnel vision Usher syndrome, which is a genetic condition that affects both hearing and vision Older adults have a greater risk of developing cataracts. Seniors are therefore more likely to have night blindness due to cataracts than children or young adults. In rare cases in the United States or in other parts of the world where nutritional diets may vary, vitamin A deficiency can also lead to night blindness. Vitamin A, also called retinol, plays a role in transforming nerve impulses into images in the retina. The retina is a light-sensitive area in the back of your eye.

Patients who have pancreatic insufficiency, such as individuals with cystic fibrosis, have difficulty absorbing fat and are at a greater risk of having vitamin A deficiency because vitamin A is fat-soluble. This puts them at greater risk for developing night blindness. People who have high blood glucose, or sugar, levels or diabetes also have a higher risk of developing eye diseases, such as cataracts. What Are the Treatment Options for Night Blindness? 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. Blood testing can measure your vitamin A and glucose levels. Night blindness caused by nearsightedness, cataracts, or vitamin A deficiency is treatable. Corrective lenses, such as eyeglasses or contacts, can improve nearsighted vision both during the day and at night. Let your doctor know if you still have trouble seeing in dim light even with corrective lenses. Cataracts Clouded portions of your eye’s lens are known as cataracts. Cataracts can be removed through surgery. 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 might recommend vitamin supplements. Take the supplements exactly as directed. Most people in developed nations don’t have vitamin A deficiency because they have access to proper nutrition. Genetic Defect Genetic conditions that cause night blindness, such as retinitis pigmentosa, aren’t treatable. The genetic defect that causes pigment to build up in the retina doesn’t respond to corrective lenses or surgery. People who have this form of night blindness should avoid driving at night. How Can I Prevent Night Blindness? You can’t prevent night blindness that’s the result of birth defects or genetic conditions, such as Usher syndrome. You can, however, properly monitor your blood sugar levels and eat a balanced diet to make night blindness less likely. Eat foods rich in antioxidant vitamins and minerals, which may help prevent cataracts. Also, choose foods that contain high levels of vitamin A to reduce your risk of night blindness. Certain orange-colored foods are excellent sources of vitamin A, including: cantaloupes eggs What Is the Long-Term Outlook? If you have night blindness, you should take precautions to keep yourself and others safe.

Refrain from driving at night as much as possible until the cause of your night blindness is determined and, if possible, treated. Arrange to do your driving during the day, or secure a ride from a friend, family member, or taxi service if you need to go somewhere at night. Wearing sunglasses or a brimmed hat can also help reduce glare when you’re in a brightly lit environment, which can ease the transition into a darker environment. Written by Marissa Selner Night Blindness To pinpoint the cause, your eye doctor will carry out a full exam. He may order specialized tests. How Is Night Blindness Treated? That depends on its cause. It may be as simple as a new prescription for glasses or a new medication . It could require surgery if cataracts are to blame. WebMD Medical Reference Reviewed by Alan Kozarsky, MD on November 29, 2015 Sources Color blindness: Night blindness at The Medical Dictionary Medicines Color blindness is usually classed as a disability; however, in select situations color blind people have advantages over people with normal color vision.

Color blind hunters are better at picking out prey against a confusing background, and the military have found that color blind soldiers can sometimes see through camouflage that fools everyone else. Monochromats may have a minor advantage in dark vision, but only in the first five minutes of dark adaptation. Prevalence Color blindness affects a significant number of people, although exact proportions vary among groups. In Australia, for example, approximately 4% of the population suffers from some deficiency in color perception. Isolated communities with a restricted gene pool sometimes produce high proportions of color blindness, including the less usual types. Examples include rural Finland and some of the Scottish islands. Causes of color blindness There are many types of color blindness. The most common varieties are hereditary (genetic) photoreceptor disorders, but it is also possible to acquire color blindness through damage to the retina, optic nerve, or higher brain areas. Higher brain areas implicated in color processing include the parvocellular pathway of the lateral geniculate nucleus of the thalamus, and visual area V4 of the visual cortex. Acquired color blindness is generally unlike the more typical genetic disorders.

For example, it is possible to acquire color blindness only in a portion of the visual field but maintain normal color vision elsewhere. Some forms of acquired color blindness are reversible. Transient color blindness also occurs (very rarely) in the aura of some migraine sufferers. Classification of color deficiencies Rod monochromacy Achromatopsia The normal human retina contains two kinds of light sensitive cells: the rod cells (active in low light) and the cone cells (active in normal daylight). Normally, there are three kinds of cones, each containing a different pigment. The cones are activated when the pigments absorb light. The absorption spectra of the pigments differ; one is maximally sensitive to short wavelengths, one to medium wavelengths, and the third to long wavelengths (their peak sensitivities are in the blue, yellowish-green, and yellow regions of the spectrum, respectively). It is important to realize that the absorption spectra of all three systems cover much of the visible spectrum, so it is incorrect to refer to them as "blue", "green" and "red" receptors, especially because the "red" receptor actually has its peak sensitivity in the yellow.

The sensitivity of normal color vision actually depends on the overlap between the absorption spectra of the three systems: different colors are recognized when the different types of cone are stimulated to different extents. For example, red light stimulates the long wavelength cones much more than either of the others, but the gradual change in hue seen as wavelength reduces is the result of the other two cone systems being increasingly stimulated as well. Several different conditions and diseases can cause night blindness. These include: Cataracts. This condition, characterized by cloudiness of the lens, can cause night blindness. Congenital night blindness. This is an inherited, stable disease in which persons suffer from night blindness. Liver conditions. Reduced night vision can be linked to poor liver functioning, due to a variety of conditions, which impairs vitamin A metabolism. Macular degeneration . Degeneration of the macula retinae, a specialized region of the retina, can cause night blindness. Retinitis pigmentosa. This is an inherited eye disease in which there is progressive deterioration of the photopigments of the photoreceptors, eventually resulting in blindness. The rods are destroyed early in the course of disease resulting in night blindness. Night blindness in children may be an early indicator of retinitis pigmentosa.

Vitamin A deficiency. Night blindness is commonly caused by a deficiency in vitamin A, in fact, it is one of the first indicators of vitamin A deficiency. Xerophthalmia. This condition is characterized by dryness of the conjunctiva (the membrane that covers the eyelids and exposed surface of the eye) and cornea, light sensitivity, and night blindness. It is caused by vitamin A deficiency. Xerophthalmia rarely occurs in countries with adequate supplies of milk products. Zinc deficiency. Zinc is a mineral that is necessary for vitamin A to improve vision. Diagnosis Night blindness can be diagnosed and treated by an ophthalmologist, a physician who specializes in eye disorders. Opticians can only dispense eye glasses but optometrists may be able to diagnose and treat vision problems. Diagnosis begins with a detailed medical history regarding the night blindness. Questions include: severity of night blindness, when night blindness began, did it occur gradually or suddenly, etc. An eye examination is performed. A slit lamp examination, in which a narrow beam of intense light is used to examine the internal components of the eye, may also be performed. Additional testing may be performed based upon the results of these standard tests.

Treatment Changes in vision should never be taken lightly. Because night blindness can be a symptom of a serious disease, an ophthalmologist should be consulted before a person embarks on self treatment. Persons who experience night blindness should not drive during the evening or at night. Additional safety precautions should be taken. Alternative remedies may be effective at reducing night blindness, particularly that caused by vitamin A deficiency. Food remedies and supplements Because night blindness can be caused by vitamin A deficiency, supplementation with vitamin A, or eating foods rich in vitamin A, may help reduce symptoms. Vitamin A was found to slow the progression of retinitis pigmentosa. Foods rich in vitamin A include dairy products, egg yolks, fish liver oil, and liver. Pregnant women should consult a physician before taking vitamin A supplements because of the link between this vitamin and birth defects. Vitamin A in humans is primarily obtained by conversion of beta-carotene, a pigment found in fruits and vegetables.

Food sources for beta-carotene include apricots, asparagus, broccoli, brussel sprouts, cantaloupe, carrots, cherries, kale, lettuce, mango, mustard greens, papaya, peaches, pumpkin, red cabbage, seaweed, spinach, sweet potatoes, watermelon, winter squash, and yams. Zinc is necessary to transport vitamin A from the liver to the retina, so zinc supplementation (up to 25 mg daily) may help improve night vision. Docosahexaenoic acid (DHA) helps to increase rhodopsin levels and lines the photoreceptor cells of the retina. DHA is converted from omega 3 fatty acids , both of which are found in certain fish oils. The suggested daily dose of DHA (from fish oils) is 500-1000 mg.

Herbal remedies Herbals which may improve night vision include: bilberry (Vaccinium myrtillus) matrimony vine (Lycii fructus, kou chi tza) berries passionflower (Passiflora incarnata) Queen Anne's lace (Daucus carota sativas) rose (Rosa species) flower eye wash yellow dock (Rumex crispus) leaves Colored light therapy One researcher found that some persons have reduced levels of photocurrent transmission (transmission of light signals from the eye to the brain) which can cause, among other things, night blindness. Colored light therapy , in which colored light stimulates the brain, can reduce night blindness caused by this photocurrent deficit. In colored light therapy, patients look at a device that cycles through 11 wave bands of color. Treatment involves 25-30 sessions over a period of four to six weeks. Allopathic treatment Night blindness caused by vitamin A deficiency will be treated with vitamin A supplements. Night vision devices are available which collect and magnify tiny amounts of light to help persons with night blindness see as well as they can during daylight. Vitamin A supplementation may slow the progress of retinitis pigmentosa.

There is no cure for retinitis pigmentosa or macular degeneration, but there are treatments, including laser surgery and the drug thalidomide, which slow down the growth of blood vessels. Cataracts require surgery. Expected results Vitamin A can effectively treat night blindness in persons who have a deficiency of this nutrient. Prevention Vitamin A may prevent night blindness and slow the progression of eye conditions, such as macular degeneration, which cause night blindness. Wearing sunglasses during the day can prevent eye damage. Key Terms Night Blindness - Encyclopedia of Alternative Medicine - altMD.com Article Night blindness Definition Night blindness is the inability or reduced ability to see in dim light or darkness. It also refers to the condition in which the time it takes for the eyes to adapt to darkness is prolonged. Description Night blindness, also called nyctalopia, is a symptom of several different diseases or conditions. All of the possible causes of night blindness are associated with the way in which the eye receives light rays. Light travels through the cornea and lens and lands on the retina at the back of the eye. The retina is composed of photoreceptors.

Photoreceptors are specialized nerve cells that receive light rays and convert them into electrical signals, which are then transmitted to the brain, creating an image. There are two types of photoreceptors, rods and cones. There are three million cones and 100 million rods in each eye. The two different photoreceptors are similar in structure, however, rods have a larger outer segment than cones. The outer segments of photoreceptors contain light-sensitive photopigments which change shape whenever light rays strike them. Rods contain the photopigments retinal and rhodopsin, whereas cones contain retinal and three different opsins. Rhodopsin is only able to discriminate between different degrees of light intensity, whereas the opsins of cones distinguish between light wavelengths in the red, blue, and green ranges. Hence, rods see only black and white, but cones see colors. Also, rods enable the eyes to detect motion and provide peripheral vision. Rods are responsible for vision in dim light, and cones are responsible for vision in bright light. The rods are spread throughout the retina, but the cones are only in the center of the retina.

Vision in dim light or darkness is blurry because of the connections between the photoreceptors and the nerve cells which are linked to the brain. Each rod must share this connection to the brain with several other rods so the brain does not know exactly which rod produced the signal. Alternatively, vision in bright light 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 feature of rods is that they must adapt to darkness. This is best exemplified by walking into a dark movie theater. At first, one can see very little. With time, vision improves and one is able to discern objects. Ultimately, one can see moderately well. This dark adaptation process occurs because of the chemical nature of rhodopsin. Rhodopsin is decomposed in bright light making the rods nonfunctional. In darkness, rhodopsin is regenerated faster than it can be decomposed. Dark adaptation takes about 15–30 minutes and, when complete, increases light sensitivity by about 100,000 times. Causes & symptoms Several different conditions and diseases can cause night blindness. These include: Cataracts. This condition is characterized by a cloudiness of the lens.

Congenital night blindness. This is an inherited, stable disease in which persons suffer from night blindness. Recent advances in gene mapping have identified several mutations responsible for this form of night blindness. Liver conditions. Reduced night vision can be linked to poor liver functioning, due to a variety of conditions, which impairs vitamin A metabolism. Macular degeneration. Degeneration of the macula retinae, a specialized region of the retina, can cause night blindness. Retinitis pigmentosa. This is an inherited eye disease in which there is progressive deterioration of the photopigments of the photoreceptors, eventually resulting in blindness. The rods are destroyed early in the course of disease resulting in night blindness. Night blindness in children may be an early indicator of retinitis pigmentosa. Recent genetic studies have identified mutations related to retinitis pigmentosa on human chromosome 19. Vitamin A deficiency. Night blindness is commonly caused by a deficiency in vitamin A, in fact, it is one of the first indicators of vitamin A deficiency. Xerophthalmia. This condition is characterized by dryness of the conjunctiva (the membrane that covers the eyelids and exposed surface of the eye) and cornea, light sensitivity, and night blindness.

It is caused by vitamin A deficiency. Xerophthalmia rarely occurs in countries with adequate supplies of milk products. Zinc deficiency. Zinc is a mineral that is necessary for vitamin A to improve vision. Diagnosis Night blindness can be diagnosed and treated by an ophthalmologist, a physician who specializes in eye disorders. Opticians can only dispense eye glasses but optometrists may be able to diagnose and treat vision problems. Diagnosis begins with a detailed medical history regarding the night blindness. Questions include: severity of night blindness, when night blindness began, did it occur gradually or suddenly, etc. An eye examination is performed. A slit lamp examination, in which a narrow beam of intense light is used to examine the internal components of the eye, may also be performed. Additional testing may be performed based upon the results of these standard tests. Treatment Changes in vision should never be taken lightly. Because night blindness can be a symptom of a serious disease, an ophthalmologist should be consulted before a person embarks on self treatment. Persons who experience night blindness should not drive during the evening or at night. Additional safety precautions should be taken. Alternative remedies may be effective at reducing night blindness, particularly when caused by a vitamin A deficiency.

Food remedies and supplements Because night blindness can be caused by a vitamin A deficiency, supplementation with vitamin A, or eating foods rich in vitamin A, may help reduce symptoms. Vitamin A was found to slow the progression of retinitis pigmentosa. Foods rich in vitamin A include dairy products, egg yolks, fish liver oil, and liver. Pregnant women should consult a physician before taking vitamin A supplements because of the link between this vitamin and birth defects. Vitamin A in humans is primarily obtained by conversion of beta-carotene, a pigment found in fruits and vegetables. Food sources for beta-carotene include apricots, asparagus, broccoli, brussel sprouts, cantaloupe, carrots, cherries, kale, lettuce, mango, mustard greens, papaya, peaches, pumpkin, red cabbage, seaweed, spinach, sweet potatoes, watermelon, winter squash, and yams. Zinc is necessary to transport vitamin A from the liver to the retina, so zinc supplementation (up to 25 mg daily) may help improve night vision. Docosahexaenoic acid (DHA) helps to increase rhodopsin levels and lines the photoreceptor cells of the retina.

DHA is converted from omega-3 fatty acids, both of which are found in certain fish oils. The suggested daily dose of DHA (from fish oils) is 500–1000 mg. Herbal remedies Herbals which may improve night vision include: bilberry (Vaccinium myrtillus) matrimony vine (Lycii fructus, kou chi tza) berries passionflower (Passiflora incarnata) Queen Anne's lace (Daucus carota sativas) rose (Rosa species) flower eye wash yellow dock (Rumex crispus) leaves Colored light therapy One researcher found that some persons have reduced levels of photocurrent transmission (transmission of light signals from the eye to the brain) which can cause, among other things, night blindness. Colored light therapy, in which colored light stimulates the brain, can reduce night blindness caused by this photocurrent deficit. In colored light therapy, patients look at a device that cycles through 11 wave bands of color. Treatment involves 25–30 sessions over a period of four to six weeks. Allopathic treatment Night blindness caused by vitamin A deficiency will be treated with vitamin A supplements.

Night vision devices are available which collect and magnify tiny amounts of light to help persons with night blindness see as well as they can during daylight. Vitamin A supplementation may slow the progress of retinitis pigmentosa. There is no cure for retinitis pigmentosa or macular degeneration, but there are treatments, including laser surgery and the drug thalidomide, which slow down the growth of blood vessels. Cataracts require surgery. Expected results Vitamin A can effectively treat night blindness in persons who have a deficiency of this nutrient. Prevention Vitamin A may prevent night blindness and slow the progression of eye conditions, such as macular degeneration, which cause night blindness. Wearing sunglasses during the day can prevent eye damage. Resources PERIODICALS Ramser, J., G. Wen, Y. Demirci, et al. "A Complete Gene Catalogue of Human Xp11.4 Harboring Disease Loci for Diabetes Mellitus Type I, Mental Retardation and Retinal Disturbances." American Journal of Human Genetics 69 (October 2001): 655. Vithana, E. N., L. Abu-Safieh, M. J.

Allen, et al. "A Human Homologue of Yeast Pre mRNA-Splicing Gene, PRP31, Underlies Autosomal Dominant Retinitis Pigmentosa on Chromosome 19q13.4 (RP11)." American Journal of Human Genetics 69 (October 2001): 229. ORGANIZATIONS night blindness facts, information, pictures | Encyclopedia.com articles about night blindness Several different conditions and diseases can cause night blindness. These include: Cataracts . This condition is characterized by a cloudiness of the lens. Congenital night blindness. This is an inherited, stable disease in which persons suffer from night blindness. Recent advances in gene mapping have identified several mutations responsible for this form of night blindness. Liver conditions. Reduced night vision can be linked to poor liver functioning, due to a variety of conditions, which impairs vitamin A metabolism. Macular degeneration . Degeneration of the macula retinae, a specialized region of the retina, can cause night blindness. Retinitis pigmentosa. This is an inherited eye disease in which there is progressive deterioration of the photopigments of the photoreceptors, eventually resulting in blindness.

The rods are destroyed early in the course of disease resulting in night blindness. Night blindness in children may be an early indicator of retinitis pigmentosa. Recent genetic studies have identified mutations related to retinitis pigmentosa on human chromosome 19. Vitamin A deficiency. Night blindness is commonly caused by a deficiency in vitamin A, in fact, it is one of the first indicators of vitamin A deficiency. Xerophthalmia. This condition is characterized by dryness of the conjunctiva (the membrane that covers the eyelids and exposed surface of the eye) and cornea, light sensitivity, and night blindness. It is caused by vitamin A deficiency. Xerophthalmia rarely occurs in countries with adequate supplies of milk products. Zinc deficiency. Zinc is a mineral that is necessary for vitamin A to improve vision. Diagnosis Night blindness can be diagnosed and treated by an ophthalmologist, a physician who specializes in eye disorders. Opticians can only dispense eye glasses but optometrists may be able to diagnose and treat vision problems. Diagnosis begins with a detailed medical history regarding the night blindness. Questions include: severity of night blindness, when night blindness began, did it occur gradually or suddenly, etc. An eye examination is performed.

A slit lamp examination, in which a narrow beam of intense light is used to examine the internal components of the eye, may also be performed. Additional testing may be performed based upon the results of these standard tests. Treatment Changes in vision should never be taken lightly. Because night blindness can be a symptom of a serious disease, an ophthalmologist should be consulted before a person embarks on self treatment. Persons who experience night blindness should not drive during the evening or at night. Additional safety precautions should be taken. Alternative remedies may be effective at reducing night blindness, particularly when caused by a vitamin A deficiency. Food remedies and supplements Because night blindness can be caused by a vitamin A deficiency, supplementation with vitamin A, or eating foods rich in vitamin A, may help reduce symptoms. Vitamin A was found to slow the progression of retinitis pigmentosa. Foods rich in vitamin A include dairy products, egg yolks, fish liver oil, and liver. Pregnant women should consult a physician before taking vitamin A supplements because of the link between this vitamin and birth defects. Vitamin A in humans is primarily obtained by conversion of beta-carotene, a pigment found in fruits and vegetables.

Food sources for beta-carotene include apricots, asparagus, broccoli, brussel sprouts, cantaloupe, carrots, cherries, kale, lettuce, mango, mustard greens, papaya, peaches, pumpkin, red cabbage, seaweed, spinach, sweet potatoes, watermelon, winter squash, and yams. Zinc is necessary to transport vitamin A from the liver to the retina, so zinc supplementation (up to 25 mg daily) may help improve night vision. Docosahexaenoic acid (DHA) helps to increase rhodopsin levels and lines the photoreceptor cells of the retina. DHA is converted from omega-3 fatty acids , both of which are found in certain fish oils. The suggested daily dose of DHA (from fish oils) is 500–1000 mg.

Herbal remedies Herbals which may improve night vision include: bilberry (Vaccinium myrtillus ) matrimony vine (Lycii fructus, kou chi tza) berries passionflower (Passiflora incarnata ) Queen Anne's lace (Daucus carota sativas ) rose (Rosa species) flower eye wash yellow dock (Rumex crispus ) leaves Colored light therapy One researcher found that some persons have reduced levels of photocurrent transmission (transmission of light signals from the eye to the brain) which can cause, among other things, night blindness. Colored light therapy , in which colored light stimulates the brain, can reduce night blindness caused by this photocurrent deficit. In colored light therapy, patients look at a device that cycles through 11 wave bands of color. Treatment involves 25–30 sessions over a period of four to six weeks. Allopathic treatment Night blindness caused by vitamin A deficiency will be treated with vitamin A supplements. Night vision devices are available which collect and magnify tiny amounts of light to help persons with night blindness see as well as they can during daylight. Vitamin A supplementation may slow the progress of retinitis pigmentosa.

There is no cure for retinitis pigmentosa or macular degeneration, but there are treatments, including laser surgery and the drug thalidomide, which slow down the growth of blood vessels. Cataracts require surgery. Expected results Vitamin A can effectively treat night blindness in persons who have a deficiency of this nutrient. Prevention Vitamin A may prevent night blindness and slow the progression of eye conditions, such as macular degeneration, which cause night blindness. Wearing sunglasses during the day can prevent eye damage. Resources PERIODICALS Ramser, J., G. Wen, Y. Demirci, et al. "A Complete Gene Catalogue of Human Xp11.4 Harboring Disease Loci for Diabetes Mellitus Type I, Mental Retardation and Retinal Disturbances." American Journal of Human Genetics 69 (October 2001): 655. Vithana, E. N., L. Abu-Safieh, M. J. Allen, et al.

"A Human Homologue of Yeast Pre mRNA-Splicing Gene, PRP31, Underlies Autosomal Dominant Retinitis Pigmentosa on Chromosome 19q13.4 (RP11)." American Journal of Human Genetics 69 (October 2001): 229. ORGANIZATIONS The Foundation Fighting Blindness. 11435 Cronhill Drive, Owings Mills, MD 21117-2220. (888) 394-3937. info@blindness.org < . OTHER Haas, Elston M. "Vitamin A." HealthWorld Online. [cited October 2002]. < . Belinda Rowland

Question: In humans, what is the medical term for night blindness, the inability to see in dim light or at night?
Answer: Nyctalopia