By: Dr. Tushar Grover, Medical Director, Vision Eye Centre, New Delhi
While night blindness or nyctalopia is a condition that sounds like a vision problem in the night, the truth is that it can impact eyesight even during the day. In fact, even in the daytime, when one is in poorly-lit indoor space or where there is dim light, one can experience this problem in the eye. In effect, night blindness involves poor adjustment of the eye in transitioning from well-illuminated surroundings to an improperly or dimly-lit place.
A symptom, not a condition
More specifically, it is not a condition in and of itself but instead a symptom of an underlying eye condition that one may have. And the symptom is not being able to see clearly and comfortably in the dark. And it takes unusually long to see clearly after moving from a lighted area to a less-lighted one. Also, when one is having problems in driving at night, it indicates the possibility of night blindness. Or when one is facing difficulty in recognizing faces in dim light. Some of the other symptoms may include cloudy vision, problem in seeing far away objects, reduced contrast sensitivity, headaches, eye pain, nausea and vomiting.
What happens to the eye in dimly-lit space?
Typically, light travels through the cornea, the anterior chamber of the eye, the pupil, the lens and posterior chamber before striking the retina. When people with night blindness enter a low light area, the rod cells in the retina – which serve as photo receptors and are responsible for converting light rays into electrical signals creating what brain interprets as images – because of some anomaly don’t function properly. As a result, the person has problem in seeing in the less-lighted area.
Causes of night blindness
Night blindness can be attributed to a wide range of eye conditions. These can be as follows: myopia, cataracts, vitamin A deficiency, glaucoma, Retinitis Pigmentosa, diabetes and usher syndrome. While in myopia, one has difficulty in seeing far into the distance, it is the clouding of the lens which leads to cataract. Due to vitamin A deficiency, there is lack of pigments needed for photoreceptor cells to function properly. Then whereas glaucoma is caused by abnormal pressure in the eye damaging the optic nerve, Retinitis Pigmentosa entails retinal damage due to genetic defects. And diabetes can lead to diabetic retinopathy and the consequent damage to blood vessels resulting in poor vision in dim light and at night. Usher syndrome is a genetic disorder characterized by hearing loss as well as Retinitis Pigmentosa.
Some are treatable, some aren’t
Of course treatment would depend on the condition which is causing night blindness. So, myopia can be addressed through simple prescription glasses and cataracts can be treated with artificial lens or surgery. For vitamin A deficiency, food rich in this nutrient apart from supplements can take care of night blindness. Glaucoma is treated with eye drops, medications and in certain cases, may require surgery as well. In Retinitis Pigmentosa, low vision aids, UV sunglasses and gene and stem cell therapies are modes of treatment. Diabetes requires good control of blood sugar levels, and if a person’s condition advances to diabetic retinopathy, injections and medications, laser surgery and vitrectomy are different ways of treatment.
Of these, the genetic conditions are nearly untreatable and therefore those having night blindness due to genetic diseases may have to live with it. However, there are eye devices and therapies that may help. Even individuals with untreatable conditions can benefit significantly from ‘Low Vision Aids’ which help improve their quality of life immensely using special devices and gadgets.
What preventive steps one should take
First of all, one should consume food items rich in vitamin A. These could be carrots, broccoli, spinach, strawberry, milk, eggs and foods rich in omega-3 fatty acids such as mackerel and salmon.
Second, one should maintain a healthy exercise and fitness regime which would keep both eye pressure and blood glucose levels in control.
Third, one should also look out and for manage chronic conditions such as diabetes and hypertension.
And lastly, one should get examined regularly by an eye doctor. At the slightest hint of having symptoms of night blindness, one should get a check-up done. Also, one should make lifestyle adjustments in response to those symptoms. For example, one should avoid driving at night in case of certain conditions with severe night vision impairment.
In sum, if one has night blindness, one should remember that even in the daytime, one would have difficult in seeing clearly in less lighted areas. So, it is not only a problem in the night.