What is night blindness?
Night blindness (Nyctalopia) is the inability to see well at night or in poor light. It is not a disease in itself, but rather a symptom of an underlying problem, usually a retina problem. It is common for patients who are myopic to have some difficulties with night vision, but this is not due to retinal disease, but rather to optical issues.
Normal vision and night blindness vision
How does night blindness occur?
Light from an object enters the eye and is bent first by the cornea and then by the lens to focus an image on the light-sensitive tissue known as the retina. Specialized receptors cells in the retina, known as rods and cones, convert the light impulses into nerve signals. These signals are then carried by nerves to the visual cortex of the brain. Here it is interpreted to allow us to perceive the light and is broadly known as the sense of vision.
However, for this to occur there has to be light reflecting off or radiating from an object in the environment. Some objects radiate their own light like the sun or an electric lamp. Other objects do not radiate light but instead reflect light in the environment. When there is insufficient environmental light like in a dark room or at night then our ability to see objects is significantly diminished and this is considered normal.
Facts and Statistics on Night Blindness
- Night blindness affects pre-school children and pregnant women the most. According to a report by WHO, night blindness globally impacts 0.9% of children and 7.8% of pregnant women.
- The proportion of cases of night blindness peaks in developing countries where health and nutrition are a constant worry. Africa and South East Asia account for nearly 2/3rd of the cases.
- The term night blindness is actually quite misleading as it implies that one is sightless at night, but as explained above, this is not the case.
What conditions cause night blindness?
Some causes of night blindness are obvious as the condition impairs the entry of light as it passes to strike the retina. Others have a more complex connection to night blindness. The causes can be divided into treatable and non-treatable.
Non treatable causes include:
- Birth defects like X-linked congenital stationary night blindness where the rods are non-functional or under-functioning.
- Retinitis pigmentosa is a condition where the retina (the light-sensitive inner lining of the eye) degenerates. It is incurable.
Treatable causes include:
- Cataracts where the lens becomes cloudy thereby reducing the intensity of light passing through it and eventually blocking the light completely (blindness).
- Myopia (nearsightedness) when uncorrected with spectacles, contact lenses or refractive surgery impairs the ability to see at night due to the elongation of the eyeball and failure of the lens to compensate.
- Drugs like those used for glaucoma which constrict the pupil and therefore limit the amount of light entering the eye.
- Diabetes which is long-standing and poorly controlled can lead to diabetic retinopathy where the retina becomes diseased as a result of damage to the tiny capillaries supplying it.
- Vitamin A deficiency is an uncommon cause of night blindness contrary to popular belief. As explained the deficiency means that rhodopsin, the pigment in rods, cannot be regenerated.
- Zinc deficiency – Zinc is a necessary co-nutrient for the eyes to be able to uptake Vitamin A. Deficiency in the US is rare.
- Sun damage – Too much exposure to intense sunlight can also damage the retina, leading to reduced night vision. Wearing 100% UVA/UVB protecting sunglasses in bright light reduces this possibility.
- LASIK eye surgery – In some cases, a side effect of LASIK is impaired night vision and the appearance of halos around lights. There is a test to determine the likelihood of this happening before undergoing LASIK.
Risk factors for Night Blindness:
Eyes / Ocular
- Retinitis Pigmentosa: Retinitis pigmentosa results in visual rods being destroyed early in the course of disease, resulting in night blindness. Night blindness in children may be an early indicator of retinitis pigmentosa.
- Macular Degeneration
- Zinc Requirement: Zinc is required in order to transport vitamin A from the liver to the retina and thus zinc supplementation, especially in those who are deficient, should help improve night vision.
- Vitamin A Requirement: Night blindness is commonly caused by a deficiency in vitamin A. It is considered one of the first indicators of vitamin A deficiency.
- Liver Detoxification / Support Requirement: Reduced night vision can be linked to a variety of conditions caused by impaired liver function which in turn reduces vitamin A metabolism.
Signs and symptoms of night blindness
- 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.
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Testing for Night Blindness
If you have difficulty seeing at night, it is important to visit your eye care professional. He or she will perform tests to determine whether you have night blindness and whether it may be connected to an underlying disease. The eye examination will include the following:
- Tests to measure your visual acuity, ability to see colors, and your pupil light reflex
- Refraction test to measure your prescription for eye glasses or contact lenses
- Slit lamp examination to examine the structures in the front of the eye, including conjunctiva, cornea, eyelids, iris, lens, and sclera
- Retinal examination to look for any damage to the structures in the back of the eye ‒ the vitreous, retina, and choroid
Your eye doctor may order an electroretinogram, which measures the electrical responses of the rods and cones (the cells in the eye that sense light) when these cells exposed to light. This test can detect abnormal function of the retina, the light-detecting portion of the eye.
You may also undergo visual field testing, which can detect central and peripheral vision problems caused by glaucoma and other eye diseases or by conditions that affect the brain, such as stroke.
Visual field testing
Night Blindness Treatment
The treatment will depend on its causes.
- Nutrients deficiency (Vitamin A and Zinc) is the easiest to treat. Just incorporate more carrots, tomatoes and green leafy vegetables for vitamin A, and beans, nuts and poultry for Zinc. If you want better protection and don’t want to eat so much food to maintain sufficient nutrients for your eye, consider taking Ocu-Plus vitamins. Ocu Plus vitamins also contains bilberry extracts which was commonly taken by pilots during WWII to improve night vision.
- If the cause is cataracts, you can go for cataracts surgery to remove the clouded lens and replace it with artificial intraocular lens. Vision is usually dramatically improved after surgery.
- For dry eye syndrome, lubricate your eyes with artificial tear drops can provide instant relief. Just make sure that they are without preservatives.
- Diabetic retinopathy can be prevented with tight control of blood sugar, active lifestyle and good dietary habits. If you already have diabetic retinopathy, there are laser and vitrectomy surgery available.
- As for retinitis pigmentosa, unfortunately there are no treatments available. Thankfully, new research is showing that vitamin A might have a slowing effect on the progression of this eye disease. But make sure that this is done under close supervision of a doctor as overdose of vitamin A can be harmful.
- Myopia (nearsightedness) can be corrected with eyeglasses, contact lens or LASIK surgery in most cases.
- Night vision glasses can be used during night time outing
Colored light therapy
- One researcher found that some persons have reduced levels of photocurrent transmission (transmission of light signals from the eye to the brain) which can cause, among other things, night blindness.
- Colored light therapy, in which colored light stimulates the brain, can reduce night blindness caused by this photocurrent deficit.
- In colored light therapy, patients look at a device that cycles through 11 wave bands of color. Treatment involves 25–30 sessions over a period of four to six weeks.
Herbals which may improve night vision include:
- Bilberry (Vaccinium myrtillus)
- Blueberry (Vaccinium) juice
- Dandelion (Taraxacum officinale)
- Eyebright (Euphrasia officinalis)
- Matrimony vine (Lycii fructus, kou chi tza) berries
- Passionflower (Passiflora incarnata)
- Queen Anne’s lace (Daucus carota sativas)
- Rose (Rosa species) flower eye wash
- Yellow dock (Rumex crispus) leaves
Prevention and Management
By treating the above conditions early it is possible to prevent night blindness. Vitamin A supplementation as a preventative measure will only be effective for night blindness due to vitamin A deficiency. It is ineffective against other causes and high doses of vitamin A can lead to toxicity. Management involves lifestyle measures that can limit the extent to which night blindness impacts on daily life and has to be considered for non-treatable causes.
- Use brighter light where necessary. This may involve brighter artificial lighting, allowing more sunlight into the home or office where possible or even carrying and using a small light source like a flashlight.
- Avoid driving at night if there is significant impairment of nighttime vision. It may be inconvenient but it can prevent serious road traffic accidents that can be fatal.
- Do not enter areas with poor lighting after being in bright light if it can be avoided. Mishaps may occur which can lead to serious medical outcomes. While most people may expect their eyes to accommodate in due course, a person with night blindness can find themselves lost within an area with poor lighting or even bump into objects or fall.
- Undergo regular eye examinations to monitor the eyesight impairment. Early treatment of some conditions can minimize the severity of the condition and even reverse it.