Impaired vision in low light conditions, such as at dusk or at night, is medically known as nyctalopia. This disorder is also known as night blindness.
Nyctalopia is not an independent disease – most often it is a symptom of a lack of certain vitamins or some pathologies that cause visual impairment.
Why is vision worse at dusk?
Vision in low light conditions is impaired due to the disruption of the light-sensitive cells in the retina: rods and cones. The latter are of three types: blue, green and red. The cones are concentrated in the center of the retina and function only in bright light. They are responsible for the perception of color and fine details. Rods are located evenly throughout the retina, and there are about 18 times more than cones. Rods perceive only white light and are responsible for black and white vision. They are much more sensitive to light than cones.
At dusk, the cones stop working because they lack light. For vision are responsible rods, through which a person sees the outlines of objects in the dark, and colors are perceived by them as different shades of gray. If for some reason the number of sticks decreases or their work is disturbed, the person begins to see worse in the dark, and he develops night blindness. The name is given to this vision disorder because chickens have only cones in the retina, so they distinguish colors well in the daytime, but see almost nothing in the dark.
But for normal vision at dusk, the eyes need time to adjust to the new lighting conditions. This process is called “dark adaptation. Sticks contain rhodopsin, a light-sensitive pigment that breaks down in light and sends a nerve signal to the vision center of the brain. A person’s night vision acuity depends on its amount. Rhodopsin is restored in the dark, but its synthesis requires vitamin A – retinol. Therefore, if there is a deficit of this vitamin, vision in the dark often deteriorates.
What are the causes of poor vision in the dark?
Deteriorating night vision is usually the result of some ophthalmic disease, but most are well treated. The most common causes of poor vision in the dark are:
- glaucoma is a group of diseases characterized by increased intraocular pressure, which leads to the gradual destruction of the retina, damage to the optic nerve and narrowing of the visual field. Some glaucoma medications cause the pupil to narrow, allowing less light to pass through, which is why glaucoma blindness becomes worse while taking them;
- Cataract – a disease characterized by partial or complete clouding of the lens of the eye. Normally, the clear lens refracts light rays and directs them to the retina, acting as a natural lens. When it becomes cloudy, this process is disrupted – less light reaches the retina, so vision, especially in low light, becomes poor. An operation to replace the crystalline lens can restore normal day and night vision with cataract;
- myopia – vision disorder in which a person sees well in the vicinity of objects, but distant distinguishes poorly, they seem to him blurred. This occurs because of impaired refraction of light in the retina;
- Vitamin A deficiency is a common cause of night blindness. It is needed to produce rhodopsin, the visual pigment responsible for the acuity of “twilight vision. Vitamin A deficiency can also occur when it enters the body with food in sufficient quantities, but poorly absorbed due to diseases of the gastrointestinal tract (such as pancreatic insufficiency) or metabolic disorders;
- Retinitis pigmentosa – a rare hereditary eye disease in which there is a gradual destruction of the light-sensitive cells of the retina, responsible for seeing in the dark (sticks). In the final stages of the pathology, a person may completely lose the ability to see in the dark. Retinitis pigmentosa is not curable, but retinal damage can be slowed by taking vitamin A, certain supplements and medications.
When visual acuity deteriorates in the dark, it is worth making an appointment with an ophthalmologist right away to find out the cause. Early diagnosis and treatment will help to avoid the development of possible complications, as well as to restore normal vision sooner.
Symptoms of nyctalopia
The main symptom of hen blindness, or nyctalopia, is impaired vision in low light conditions. However, it can manifest itself in different ways – some cannot see stars in the night sky, some have difficulty navigating a dark room. A questionnaire developed by experts at the American Academy of Ophthalmology will help you determine if you have symptoms of nyctalopia:
- I have difficulty moving around the house in dim lighting;
- I cannot see well at night, so I have difficulty driving at night;
- I have difficulty recognizing faces in low light;
- It takes me a long time to get used to bright light after being in a dark room;
- It takes me a long time to see in a dark room after lights out.
If you answered more than one question in the affirmative, you most likely have nyctalopia. However, only an ophthalmologist can confirm or disprove this during an examination.
Chicken blindness may also be accompanied by other symptoms. Their nature depends on which eye disease they are caused by. Such symptoms include:
- Pain in the eyes;
- blurred vision or double vision;
- Increased sensitivity to light;
- deterioration in the acuity of distant vision.
What vitamins prevent chicken blindness?
Visual acuity depends largely on whether the body has enough nutrients and vitamins necessary for proper visual function. The following vitamins play an important role in preventing hen blindness and maintaining eye health:
- Vitamin A – is essential for maintaining normal corneal moisture levels. It is the main vitamin that can prevent night blindness because it is a component of rhodopsin, the protein responsible for night vision. According to some studies, a diet high in vitamin A can reduce the risk of cataracts and age-related retinal maculodystrophy. The vitamin is not synthesized in the body and comes into it only with food. It is found in large amounts in carrots, pumpkin, milk, eggs, butter, potatoes, and green leafy vegetables;
- Vitamin E is a powerful antioxidant. It protects cells throughout the body, including the eyes, from free radicals, unstable molecules that cause damage. Vitamin E slows the aging process, allows you to delay the development of age-related farsightedness. Most of it is contained in nuts, seeds, vegetable oil, salmon, avocados and green leafy vegetables;
- Vitamin C (ascorbic acid), like vitamin E, is a strong antioxidant that protects eye cells from the damaging effects of free radicals. Vitamin C is also essential for the synthesis of collagen, the protein that makes up the cornea and sclera of the eye. Regular intake of vitamin C supplements reduces the risk of cataracts by 45%. Ascorbic acid is found in citrus and tropical fruits, white cabbage, and broccoli;
- vitamins B6, B9, and B12. Their combination can reduce levels of homocysteine, a protein associated with inflammation in the body and an increased risk of age-related retinal macular dystrophy;
- Vitamin B2 (riboflavin), an antioxidant that reduces oxidative stress in the body. Long-term riboflavin deficiency can increase the risk of cataracts – many people with this disease have been found to be deficient in this vitamin. Daily intake of 1.6-2.2 mg of riboflavin reduces the risk of cataracts by 31-51%. The daily recommended amount of vitamin B2 is 1.1-1.3 mg. It is easy to dial in because it is found in many foods – milk, yogurt, beef, oats, and other whole grains;
- Vitamin B3 (niacin) is an antioxidant that can significantly reduce the risk of glaucoma. However, supplements containing it should be taken with caution – when taken in high doses (1.5-5 grams per day) niacin can cause corneal inflammation and visual impairment. Vitamin B3 is found in large amounts in beef, poultry, fish, mushrooms, peanuts, and legumes.
In addition to vitamins, omega-3 fatty acids are essential for maintaining healthy eyes. They have anti-inflammatory properties and reduce the risk of diabetic retinopathy – retinal vascular lesions. Omega-3 fats are useful for eye diseases accompanied by dryness of the cornea, since they increase its moisture content. In order to increase the amount of omega-3 fatty acids in your diet, you should include oily fish, flax or chia seeds, soybeans, nuts, and olive oil.
What are the dangers of chicken blindness?
Chicken blindness is often a symptom of an eye disease, so it should not be ignored. When night vision deteriorates, it is necessary to see a doctor immediately. The sooner treatment is given, the greater the chance of avoiding the development of complications, which are not always reversible.
Night blindness is one of the symptoms of dry eye syndrome (xerophthalmia) caused by vitamin A deficiency. In the absence of timely therapy, the tear ducts dry out and the cornea softens, resulting in permanent vision loss.
Chicken blindness also poses an increased risk of injury – a person who cannot see well in the dark can trip and fall, injuring themselves. Deteriorating vision at dusk is also dangerous on the road. With night blindness, the field of vision is narrowed, so the driver may not see the obstruction from the side.
Nyctalopia is often accompanied by disorder of dark adaptation – a person gets used to the light for a long time after being in the dark and vice versa. This is especially dangerous on the road, as it creates a potential accident situation. The headlights of oncoming cars periodically shine in the driver’s face, which makes him go blind for a while and lose control over what is happening.
Is it possible to cure night blindness?
It is possible to get rid of night blindness only if the disease that caused it can be cured. Sometimes nyctalopia can be cured by choosing the right glasses or changing the medication (for example, for glaucoma). In some cases, only surgery can improve vision – for example, replacement of the lens for cataracts.
Most of the diseases that cause night blindness are successfully treated. The only exception is retinitis pigmentosa. There is no cure for this rare genetic disease yet, but it can be controlled by slowing the rate of retinal damage.
Poor vision in the dark or nyctalopia is a reason to have your vision checked by an ophthalmologist. Sometimes to restore it, it is enough to review your diet and add to your diet foods rich in vitamins A, E, C and B group, as well as healthy omega-3 fats contained in olive oil.