Everyone’s vision is reduced in low light conditions. Nevertheless, some have particular difficulties at night in such conditions. This is known as night-blindness or nyctalopia.
How is night vision different from daytime vision?
Night vision is different from daytime vision. At night, the ability to perceive colour is reduced and our vision is practically limited to black, white and grey. Our general ability to see (visual acuity) is also reduced and there is an area in our central field of vision in which we see less clearly. In addition, moving objects are easier for us to see than static ones.
What causes night-blindness?
Night-blindness does not completely impede night vision, but it does make it considerably more difficult. It is not a separate condition, but rather a symptom which can be a sign of another kind of vision problem.
In some cases, severe myopia can make it more difficult to see at night or in low light conditions.
There are specific cells in our retina (the lining at the back of the eye) which are responsible for vision in low-light conditions. When these cells are affected by illness or vision problems, this can cause night-blindness.
- illnesses and eye conditions that can cause nyctalopia include:
- severe myopia;
- glaucoma (a disease which affects the optic nerve)
- the glaucoma drugs that contract the pupil
- cataracts (when the lens of the eye becomes clouded)
- retinitis pigmentosa (an eye disease which can lead to blindness)
- keratoconus (when the outer layer of the eye, the cornea, thins and becomes deformed)
Is it normal to bump into things or trip at nighttime, or could this be a sign of vision problems?
If you are unsure whether or not you are suffering from night-blindness, responding to these questions may help you:
- Do you have problems moving around in your house, even when some lights are on?
- Do you find it hard to drive at night?
- Do you avoid going out at night for fear of falling?
- Do you have difficulty recognizing people in places with low lighting?
- Does it take you a long time to adapt to the light when you go out in dimly lit places or to adapt to the dark when you enter a dimly lit bedroom?
If you are worried about your night vision in low-light conditions, make an appointment with an ophthalmologist. They will carry out a thorough exam that will be able to detect whether or not you have any vision problems.
Can it be treated?
Treatment for nyctalopia depends entirely on its cause. If it is due to a refractive error, then all that may be required is a new prescription. If you have a cataract then removing it may improve your night vision. Your ophthalmologist will carry out the necessary tests to determine the cause of your night-blindness and tell you what the prospects are for improvement.