Causes of Night Blindness / Nyctalopia

driving at nightNight blindness, also called “Nyctalopia”, is a condition characterized by the inability to see well or to see at all in low light. It can also give a diminished ability to see contrast and difficulty transitioning from bright light to dim light. Night blindness has many causes, some that are treatable and some that are not.

In order to understand night blindness, one must understand a little about how the eye works. The retina is located in the back part of the eye, where light falls after passing through the lens. The retina has two types of cells that respond to light: rods and cones. Cones receive bright light and interpret color and detail. They are primarily located in the center of the retina and comprise 10% of light-receiving cells. The other 90% of cells are rods. Rods “see” in grayscale and provide much of our night time vision. They do not pick up color. They are most concentrated at the edges of the retina and fade away toward the center. Because they see in grayscale, rods are the cells that work for us in low lighting conditions. When the rods become damaged, they stop being able to pick up low light signals, resulting in no or little visual information transmitted through the optic nerve to the brain.

Common causes of untreatable night blindness include the following conditions.

  1. X-linked congenital stationary night blindness – This type of night blindness is, as the name says, congenital. It is caused by a genetic defect and comes in two forms: complete and incomplete. With complete night blindness, the rods do not respond to light at all. There is no ability to see in low light conditions. With incomplete CSNB, the rods respond to light with a diminished capacity. There is a limited ability to see in low light conditions. CSNB of both types often co-occurs with reduced visual acuity, myopia, nystagmus and strabismus. There is no known treatment for it.
  2. Retinitis Pigmentosa – Another disease caused by genetic defect, retinitis pigmentosa is characterized by dark spots on the retina. Usually vision problems begin in childhood and worsen throughout life. Typically, it is the rods that are affected. But in severe cases, the cones can be affected as well. Because the rods are concentrated at the edges of the retina, this condition can also lead to “tunnel vision”. There is also no known treatment for it although wearing sunglasses in bright light may help to preserve vision. Some studies have indicated supplementation with antioxidants may be helpful including Vitamin A,C and E, omega-3 fatty acids, lutein and alpha lipoic acid . There are additional studies underway to evaluate if essential fatty acids can help, particularly DHA, found in fish oil.

Common causes of treatable night blindness include the following conditions.

  1. Vitamin A deficiency – Vitamin A deficiency was a common occurrence in the early industrialized world. This was the primary reason for adding Vitamin A to dairy products. Now Vitamin A deficiency in the United States is rare and occurs almost exclusively due to an inability to absorb it. A number of conditions can lead to this problem. They include Crohn’s disease, cystic fibrosis, celiac disease, pancreatic insufficiency and/or low thyroid function. In such cases, supplementation with Vitamin A may be helpful but levels have to be monitored because Vitamin A in very large doses can be toxic to the liver over time. If the problem is caused by celiac disease, taking care to avoid gluten and consuming probiotics can help to restore sufficient intestinal health for proper Vitamin A absorption.
  2. Zinc deficiency – Zinc is a necessary co-nutrient for the eyes to be able to uptake Vitamin A. Deficiency in the US is rare.
  3. Diabetes – Elevated blood sugar levels damage many tissues in the body including the eyes. Sugar adheres to cells in a process known as “glycation”. Just as sugar becomes very sticky outside of the body, it also becomes sticky inside the body. Once it adheres to cells, it tends to stay put, damaging their ability to function. Over time, glycation can cause damage to the eyes including the retina, a condition known as retinopathy, and result in the formation of cataracts. Two early indicators of eye damage in diabetics include poor night vision and trouble adapting to indoor light after being outside. This problem is minimized by tightly controlling blood sugar levels.
  4. Cataracts – As we age, cell turnover in the body slows. In the eye, this causes debris to accumulate in the lens. People often do not notice cataracts early because the accumulation of debris is slow and progresses over time. Early signs of cataracts are reduced night vision, the appearance of halos around lights and blurry vision.
  5. LASIK eye surgery – In some cases, a side effect of LASIK is impaired night vision and the appearance of halos around lights. There is a test to determine the likelihood of this happening before undergoing LASIK.
  6. Sun damage – Too much exposure to intense sunlight can also damage the retina, leading to reduced night vision. Wearing 100% UVA/UVB protecting sunglasses in bright light reduces this possibility. Amber or brown color lenses are the best to filter out blue light as well.

Our eyes are made of sensitive tissues and vision is our most relied upon sense. Proper eye care goes a long way towards maintaining quality of life for most individuals. In cases where the cause of night blindness is treatable, taking care of the primary condition is of paramount importance. Supplements that have been shown to benefit eye health may also help ward off the loss of night vision. Possible supplements to consider when thinking about eye health include:

  1. Essential fatty acids which are found in fish and fish oil supplements. They maintain the health of cell membranes and reduce inflammation which is a contributing factor to many degenerative diseases.
  2. Antioxidants – Lutein and zeaxanthin, which are both antioxidant carotenoids found in green leafy vegetables have shown benefit in numerous studies for eye diseases, particularly age-related macular degeneration and cataracts. These carotenoids are found in both in the retina and lens of the eyes, and act as a sort of “internal pair of sunglasses” filtering out UVA and UVB light.
  3.  Turmeric – A potent anti-inflammatory agent, turmeric also has the ability to direct cells to perform properly, thereby reducing all kinds of cellular malfunctions.

Should you have or develop night blindness, it is very important not to perform dangerous activities in low light, particularly driving, a universal American activity. Driving in low light with poor night vision is extremely dangerous! Night blindness should not be self-diagnosed. An eye doctor should be consulted on a regular basis to screen for eye disease and damage.

Next: Nutritional support, diet, & lifestyle tips for night blindness.