Night blindness

What is Night blindness?

Nyctalopia (from Greek νύκτ-, nykt- "night"; αλαός, alaos "blind, not seeing", and ὄψ, ops "eye"), also called night blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition (for example, a lack of vitamin A). It can be described as insufficient adaptation to darkness.

The most common cause of nyctalopia is retinitis pigmentosa, a disorder in which the rod cells in the retina gradually lose their ability to respond to the light. Patients suffering from this genetic condition have progressive nyctalopia and eventually their daytime vision may also be affected. In X-linked congenital stationary night blindness, from birth the rods either do not work at all, or work very little, but the condition doesn't get worse. Another cause of night blindness is a deficiency of retinol, or vitamin A, found in fish oils, liver and dairy products.

The opposite problem, the inability to see in bright light, is known as hemeralopia and is much rarer.

Since the outer area of the retina is made up of more rods than cones, loss of peripheral vision often results in night blindness. Individuals suffering from night blindness not only see poorly at night, but also require extra time for their eyes to adjust from brightly lit areas to dim ones. Contrast vision may also be greatly reduced. Rods contain a pigment called rhodopsin. When light falls on rhodopsin, it undergoes a series of conformational changes ultimately generating electrical signals which are carried to the brain via the optic nerve. In the absence of light, rhodopsin is regenerated. The body synthesizes rhodopsin from vitamin A, which is why a deficiency in vitamin A causes poor night vision.

Refractive "vision correction" surgery (especially PRK with the complication of "haze") may rarely cause a reduction in best night-time acuity due to the impairment of contrast sensitivity function (CSF) which is induced by intraocular light-scatter resulting from surgical intervention in the natural structural integrity of the cornea.

Questions and answers on "Night blindness"

Am 20 years old and am having night blindness . I have checked with many doctors but they said there is no prevention for this. what to do? can you...

doctor1 MD

Hello dear
Thanks for your query.

There are multiple causes of night blindness like --
Retinitis pigmentosa
oguchi disease
pathological myopia...

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hi this s selevdarn from tamilnadu,,, and my mather is 60 years old a retd teacher ... he s suffering from night blindness... now he getting worse...

doctor1 MD

Welcome to Health care Magic.

I reviewed your history.
It seems from the history that your mother is having night blindness secondary to a...

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Hi. I smoke weed for medical use and lately When I m high I ve been getting a very intense tingling sensation in my just under my belly button...

doctor1 MD

Hi there ~

I understand your concerns. If you are smoking medical marijuana, there is a possibility of its side effects including the ones that you...

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