Night blindness (impaired dark adaptation) is the experience of reduced night vision. It typically causes people to not be able to see well in the darkness but be able to see without problem when it is not dark. This condition, unless accompanied by other eye pathology, is not true blindness; even at nighttime, the eye is not "blind" but occurs because the rods of the photoreceptor cells which are needed for dim light are not functioning correctly.
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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.
- Vitamin A deficiency
- 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
- See our recommendations for diet / lifestyle.
- Vegetables. Vitamin A rich vegetables such as dark green vegetables like spinach, collards, and orange and yellow vegetables such as carrots and sweet potatoes.
- 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.
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.
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 (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 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
1. Zinc supplementation might potentiate the effect of vitamin A in restoring night vision in pregnant Nepalese women
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
6. Trace Elements & Night Blindness (2011)
7. The Biology of Taurine: Methods and Mechanisms
Also see research on night blindness.