What Causes Night Blindness?

Published October 21, 2020

Night blindness (nyctalopia) causes reduced vision in low light conditions, and can be a source of fear and anxiety for those affected by it.  

Decreased night vision can significantly impact a person’s quality of life— affecting the ability to drive after dark, and increasing the risk of accidents.

How does night vision work?

In order to be able to see well at night, or in low light conditions, your eyes need to adjust appropriately.

The first necessary adjustment involves your pupils. When exposed to a dark or dimly lit environment, your pupils will dilate, or become larger, to enable more light to enter your eye. This light will then move through a series of essential steps in order to be received by the retina.

The retina is the light sensitive tissue in the back of your eye that contains all of the photoreceptor cells, called rods and cones.

  • Cone cells provide color vision, enabling us to see during the day, and in bright light.
  • Rod cells provide black and white vision, enabling us to see in the dark. For this reason, night vision is all or mostly, black and white.

Decreased night vision or total night blindness can occur when the rods stop working, usually as a result of an eye injury, condition or disease. 

In some cases, poor night vision can be a temporary side-effect of another condition or even a natural part of the aging process.

Eye conditions that can cause night blindness

Night blindness is generally a symptom of an underlying ocular condition that involves the health of the retina, though it can also result from severe or worsening myopia, or a vitamin A deficiency.

  • Vitamin A deficiency is one of the most common causes of night blindness. An insufficient amount of vitamin A in the body affects the production of rhodopsin, the necessary pigment for night vision. Night blindness is usually one of the first signs of a vitamin A deficiency.

 

  • Cataracts generally develop as part of the natural aging process, as the proteins that make up the eye’s lens begin to crystallize and harden. Cataracts affect vision clarity, causing blurriness, glare and the presence of halos around bright lights. Decreased night vision and increased difficulty driving at night is typically the first sign of a developing cataract.

 

  • Glaucoma occurs when the pressure within the eye increases and causes progressive damage to the optical nerve. This disease affects both daytime and nighttime vision— first affecting peripheral vision, and then central vision.

 

  • Macular degeneration is an eye disease that affects retinal health, and causes blind spots and image distortions in both daytime and nighttime vision.

 

  • Diabetes can affect the shape of the eye’s lens and cause damage to the blood vessels in the eyes— leading to a condition called diabetic retinopathy. One of the first symptoms of diabetic retinopathy is poor night vision.

 

  • Retinitis pigmentosa is a retinal disease that occurs when dark pigment collects in the retina, causing the rod cells to breakdown. This disease makes it difficult to see in low light conditions, and can lead to tunnel vision and eventually total vision loss.

 

  • Congenital conditions that cause problems with the eye’s pigmentation can decrease night vision or cause total night blindness. A common congenital disorder associated with night blindness is called Usher Syndrome.

 

  • Nearsightedness (myopia) occurs when distant images and objects appear blurry. If you cannot see clearly during the daytime, or if you need a new optical prescription, your vision in low light will be just as blurry as your daytime vision.

 

  • Refractive surgeries such as Lasik and PRK, change the shape of the cornea to improve vision— but in doing so, can affect the way light bends as it enters the eye. As a result, glare and halos around street lights and headlights can affect your vision at night.

Do I have night blindness? 

Since night blindness can be caused by a number of underlying conditions, symptoms can vary. 

The most common signs of night blindness include:

  • Blurry or cloudy vision in low light
  • Sensitivity to light
  • Seeing glare or halos around lights
  • Difficulty seeing distant objects in low light
  • Inability to see stars in the night sky
  • Total loss of vision when entering a dark room (lasting more than a few minutes)
  • Trouble seeing objects or faces in low light conditions

If you are experiencing any of these symptoms, schedule an appointment with your eye doctor as soon as possible.

Your eye doctor will ask you questions about your medical history and perform a series of tests to identify signs of an ocular disease or vision condition.

To learn about night blindness treatments and preventions, click here.