Night blindness – also known as nyctalopia – does not actually imply you’re blind, but rather it means that seeing at night is becoming increasingly difficult. Nyctolopia is not limited to the night time only and can also be experienced during the day in a dim-lit room.
Normally, our eyes are supposed to adjust to the changes in light exposure fairly quickly. This allows for a smooth transition without any complications. Those affected by night blindness either need too much time to adjust or can’t do properly. This increases the risk of injury and other complications, as one’s vision becomes impaired in the absence of adequate lighting.
In a clear vision, light reflecting off an object enters the eye, and is bent by the cornea and then by the lens to focus an image onto the retina. Receptor cells in the retina – rods and cones – convert the light impulses into nerve signals, which are sent to the brain’s visual cortex. This is where the image is processed, and this is what is known as the sense of vision.
Our night vision is diminished because of insufficient light to reflect off the object – for example, at night or in a dark room – and it’s normal. The intensity of reflected light stimulated the receptor cells that adjust to new conditions. The problem of night blindness arises when there’s abnormality in stimulation of these photoreceptors. One of the culprits is a vitamin A deficiency, which affects the levels of rhodopsin, a pigment in receptor cells participating in the adjustment processes.
Health conditions, too, can affect the receptors in the retina, further contributing to night blindness.
Health conditions that can contribute to night blindness are birth defects, retinitis pigmentosa, cataracts, myopia, glaucoma drugs, longstanding or uncontrolled diabetes, diabetic retinopathy, and, as mentioned, a vitamin A deficiency.
The main symptom of night blindness is the inability or difficulty to see at night or in darkness. This is most likely to occur during the transition from one light exposure to the other. For example, when you enter a dark room, when you shut off the lights, or when the sun is setting.
Night blindness is problematic as it can increase a person’s risk of injury or slow them down.
If you begin to notice that adjusting from light to dark is becoming more challenging for you and taking longer than usual, you may wish to speak to your doctor. They will aim to uncover the underlying cause and treat your condition.