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Night Blindness

Are you in the dark?

iStock_000036850160_FullMdm Minah had been healthy and independent all her life until her fifties, when she noticed she had difficulty seeing at night.

“I used to go out at night to buy supper for my boys who would come home hungry after their afternoon shift. But lately, I realised that everything outside the house seemed so dark. I dismissed it simply as age catching up and perhaps, all I needed was just a new pair of glasses.”

One evening, she had a nasty fall while venturing out alone to run an errand. Her two worried sons took her to her family doctor. After treating her injury, the doctor checked her vision and was appalled that she could only see silhouettes in dim lighting, although her daytime vision seemed perfectly normal. An eye specialist diagnosed it as retinitis pigmentosa, a condition in which vision drops sharply at night, resulting in night blindness.

Night blindness or nyctalopia is not a disease but an underlying abnormal eye condition where one’s eyes refuse to function at night or in low light conditions. This has severe consequences for the sufferer as it means a loss of mobility at night.

What causes night blindness?

It can be caused by the following eye conditions:

  1. Cataracts – The increasing opacity of the human lens causes blurring of vision even in daylight and worsens in dim light or at night.
  2. Severe short-sightedness (high myopia) – Night blindness may be a symptom of undiagnosed or progressive myopia.
  3. Diabetes affecting the retina (diabetic retinopathy) – Diabetes affects the small blood vessels in the retina, causing damage to the photoreceptors which are responsible for receiving visual images. In dim conditions, the photoreceptors function even more poorly.
  4. Vitamin A deficiency – Vitamin A is necessary to keep the retina healthy. However, a deficiency in this vitamin is rare.
  5. Retinitis pigmentosa (usually hereditary) – This is a rare and untreatable condition. This ailment tends to run in the family and may plague both the young and elderly.

Am I at risk of developing night blindness?

Think about the following questions:

  1. Do you take a long time making out images at night?
  2. Do you have any family member with night blindness?
  3. Do you have short-sightedness above 700 degrees?
  4. Do you have diabetes mellitus?

If you answer “Yes” to any of the above, it is advisable to see an eye specialist at least once yearly.

normal vision

Normal night vision

diminished vision

Diminished night vision (Notice the loss of details)

 

 

 

 

 

 

 

 

 

What happens at an eye specialist visit?

At the Eye Specialist clinic, you will be given a comprehensive eye examination which comprises a visual acuity check, intra-ocular pressure measurement as well as a refractive error check. A retinal examination is then performed to detect any retinal diseases. Sometimes, a night adaptation test may be performed to assess the severity of the condition.

How can night blindness be treated?

The mode of treatment for night blindness depends on its cause. It may be as simple as prescribing a new pair of glasses, to surgically removing the cataract. For diabetic patients, advice on a low sugar level diet will help stabilise their visual condition.

Night blindness caused by Vitamin A deficiency is easily treatable by prescribing Vitamin A supplements or encouraging the consumption of food rich in Vitamin A such as sweet potatoes, carrots and dark green leafy vegetables.

To date, no active treatment is available for retinitis pigmentosa, although recent studies on the use of oral valproic acid have reported an improvement in visual function.1

Does LASIK cause night blindness?

A number of my patients who have had their LASIK procedure done are concerned about LASIK causing night blindness. I assured them that although LASIK may initially cause nocturnal visual disturbances like “haloes”, such “halo” disturbances usually subside after a month.

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Clinical Associate Professor Goh Kong Yong is a Senior Consultant Ophthalmologist at Dr Goh Eye Neuro-ophthalmic and Low Vision Specialist, Mount Elizabeth Novena Hospital, Singapore.
Posted by ezyhealth on Dec 5 2014. Filed under Eye Health. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.

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