Posted by: courtneygrapperhaus | June 28, 2015

Exploring Night Vision & Night Blindness

Until about 6 or 7 years ago, I never had to wear glasses. It wasn’t until I began having problems seeing to drive at night that I went for an eye exam as an adult. Millions of people have problems with night vision. But what exactly is it and how is it caused?

“Night vision is the ability to see in low light conditions.” (Wikipedia). RETINALBiologically, human eyes can adjust to night vision on their own (to a certain extent). Photoreceptor proteins in the eye must be recharged with active retinal to allow us to see in the dark. The entire process takes about 45 minutes, but most of the adjustment takes place within the first 5 minutes.

There are several technologies that exist to enhance human night vision beyond its natural ability. These include night glasses, low light cameras, and thermal imaging. Not too long ago, night glasses were the only option. Current technology has brought us NVDs (night vision devices). NVDs are usually used by the military, but more and more civilian uses are becoming popular (for example pilots, hunters and drivers of premium vehicles). Perhaps the most well known NVDs are night vision goggles (often featured in military video games and movies). Have you ever wondered why everything looks green through these?

View through military night vision goggles

View through military night vision goggles

Even at night, the photons that hit the lens at the front of night vision goggles are carrying light of all colors. But when they are converted to electrons, there’s no way to preserve that information. Effectively, the incoming, colored light is turned into black and white. Why, then, don’t night vision goggles look black and white? The phosphors on their screens are deliberately chosen to make green pictures because our eyes are more sensitive to green light. It’s also easier to look at green screens for long periods than to look at black and white ones (that’s why early computer screens tended to be green). Hence, night vision goggles have their characteristic, eerie green glow. (

Poor night vision may be referred to as “nyctalopia” or “night blindness”. Symptoms of night blindness include halos, blurred vision, delayed adaption period between bright and low light, and weak vision in dimmed light. If you are experiencing any ongoing symptoms you should visit an Eye Care Professional and get a dilated eye exam. The doctor may ask you questions about your symptoms, ask you about your medical history, use a slit lamp to examine your eyes, and perform color blindness and visual acuity tests.

night vision

What a person with poor night vision sees when driving

If you have poor night vision or night blindness, there are several potential causes. These include…

  • Cataracts
  • Vitamin A or Zinc deficiency
  • Nearsightedness
  • Retinitis pigmentosa
  • Sunlight exposure (“sustained bright sunlight can impair nigh vision for up to 2 days” according to WebMD)
  • Diabetes
  • Complications from LASIK surgery

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