Walking or driving in the dark can be disconcerting for anyone. But for those who experience what's known as night blindness, moving about in poorly lit surroundings is not only unsettling — it can be downright dangerous. Here's what to know about why some people have more trouble seeing in low light than others.
What is night blindness?
Night blindness is a specific kind of vision impairment. It is not a condition or disease in and of itself, but rather a symptom of an underlying problem. “The word is a bit misleading,” says Melissa Yao, M.D., assistant professor in the Department of Ophthalmology & Visual Sciences at Albert Einstein College of Medicine and Montefiore Medical Center, in New York City. “The symptom is not confined to the nighttime, nor does it mean that you're totally blind. The medical term that we use, which is more accurate, is ‘nyctalopia,’ which means the inability to see well in the dark or dimly lit conditions.”
You may notice that you have more trouble recognizing people's faces in darkened settings, worry about tripping and falling while walking inside your home or outside in dark conditions, and can't see as well when driving at night, for instance.
Causes of the condition
A quick anatomy lesson: Light enters the eye through the cornea, passes through the pupil (the tiny opening in the center of the iris), then hits the lens, which focuses light rays onto the retina (the thin, light-sensitive tissue that lines the back of the eye).