In night blindness, medically called hemeralopia, vision at dusk is impaired. Responsible for this is a functional weakness of the rods. These are the sensory cells of the retina that enable vision in low light conditions.
What is night blindness?
Night blindness can be congenital, but it can also be caused by a condition such as diabetes or vitamin A deficiency. How night blindness progresses depends on this. In almost all cases, night blindness is not curable. In the narrower sense, night blindness means that you can no longer see anything at all at night or in the twilight. This is very rare, most patients affected by night blindness simply see worse at night. In both cases, it is still referred to as night blindness.
Causes
In either case, the cause of night blindness is a disorder of the rods. These sensory cells in the retina enable vision at dusk. Such a dysfunction of the rods can be triggered by many different causes. Therefore, in the case of night blindness, it is always advisable to be examined by an ophthalmologist. Vitamin A deficiency is very rare in industrialized countries. Vitamin A is necessary for light-dark vision and leads to visual disturbances in the dark if it is present in insufficient amounts. Vitamin A deficiency can occur, among other things, if not enough food containing the vitamin is eaten or if sufficient intake is not possible because of a stomach or intestinal disease. Far more often, congenital conditions are responsible for night blindness. In some people, the rods simply function worse. This form of night blindness is often accompanied by myopia and eye tremor (nystagmus). But the rather rare retinopathy pigmentosa can also lead to night blindness. In this disease, the sensory cells of the retina are attacked by the body’s own processes and gradually lose their function. Other physical diseases such as diabetes can also cause night blindness if the fine vessels in the eye are damaged by the diabetes. Not night blindness in the strict sense are the vision problems caused by a cataract (clouding of the lens). Patients with cataracts simply notice more blurred vision at dusk and are blinded by incoming light. By the way, it is normal if you don’t see anything for the first few minutes after going from light to a dark room. It takes the eye a few minutes to adjust to changing light conditions.
Symptoms, complaints, and signs
In night blindness, vision problems occur in low light conditions. The eye is no longer able to adapt to twilight or darkness and responds to rapid changes in brightness with vision problems and blindness. Patients often notice a gradual deterioration in night vision, often associated with symptoms such as eye tremor or myopia. If night blindness is caused by a retinal disease (such as retinopathy pigmentosa), visual field defects also occur. In the further course, complete blindness may occur in one or both eyes. If vitamin A deficiency is the cause, hemeralopia is often accompanied by very dry eyes and itching or pain. In addition, other visual disturbances such as color vision problems and double vision set in. The symptoms of night blindness can be congenital or occur as a result of a disease or an accident. People between the ages of 30 and 50 are predominantly affected. The hereditary form develops shortly after birth. Affected children suffer from myopia, visual field defects and visual complaints in limited light conditions already in the first two years of life. A progressive course leads to partial or complete blindness in individual cases before adulthood.
Diagnosis and course
To diagnose night blindness, the ophthalmologist first examines the dark adaptation of the eyes, i.e., how well and quickly your eyes can adapt to changing light conditions. An adaptometer is used for this purpose. In addition to dark adaptation, this device can also be used to measure how sensitive to glare and how nearsighted you are at dusk. The causes of night blindness are then sought.Among other things, an electroretinogram is used for this purpose. This device can be used to check the functionality of the sensory cells in the eye: The rods, which are responsible for seeing in the twilight, and the cones, the sensory cells for color vision. The course of night blindness depends on its cause. If the night blindness was inherited from the parents, it will usually not worsen over time. Retinopathy pigmentosa, on the other hand, gradually leads to greater visual impairment, which also affects night blindness.
Complications
Night blindness in the strict sense is the complete loss of function of the rod photoreceptors, whose greatest density is located on the retina outside the macula, the site of sharp color vision. The rods are characterized by strong light sensitivity and by high sensitivity to moving objects, but do not provide any color vision. In most cases, however, night blindness masks only limited night vision, which is most noticeable in the form of an unpleasantly increased sensitivity to glare when driving at night. If the night blindness is based on a genetically caused malposition of the rods, the limited vision at dusk and night does not change further in the further course. If the night blindness is acquired, the further course depends on the cause. If it is only a vitamin A deficiency due to an unbalanced diet or because the absorption capacity of the intestinal tract is limited due to an intestinal disease, the symptoms improve when the metabolism can again dispose of a sufficient amount of vitamin A. The symptoms are then corrected. If the problems are due to damage to the vascular system in the retina, which may be caused, for example, by an excessively high sugar concentration in the blood due to unrecognized type 2 diabetes, the prognosis for progression is unfavorable if the disease continues to be ignored and not treated. Another causative factor of night blindness may also be genetic retinopathy pigmentosa, which is usually associated with very slow disease progression.
When should you see a doctor?
Decreased vision during darkness is a natural occurrence that does not need to be investigated or treated. However, if further discomfort occurs or if the inability to see begins at dusk, a follow-up visit to a doctor should be made. If one’s own vision differs in direct comparison to other people, a visit to the doctor should be made. If the surrounding objects or other persons can only be perceived dimly or blurred, a check-up visit to a doctor is necessary. Trembling of the eyes, pain in the area of the eyes or headaches are signs of a present irregularity. If there are more accidents or falls due to the reduced vision, a visit to the doctor is recommended. Severe nearsightedness or the feeling of blindness when light levels decrease should be investigated and clarified. Facial deficits are of particular concern as they are a clear sign of an existing disease. If emotional or mental irregularities occur in addition to physical impairments, a physician should also be consulted. Behavioral abnormalities, aggressive tendencies, anger, and withdrawal from participation in social life are unusual. If there is a depressive appearance, mood swings, or an increased potential for conflict, the observations should be discussed with a physician.
Treatment and therapy
Treatment of night blindness depends on the diagnosis. Unfortunately, if night blindness is congenital, no promising treatment method is known to date. Also, damage to the fine vascular system of the eye and the retina, for example due to diabetes, cannot be reversed so far. If vitamin A deficiency in the diet or a gastrointestinal disorder has triggered the night blindness, the visual disturbances at dusk usually stop again when the underlying problem is eliminated.
Outlook and prognosis
Night blindness in itself does not result in a shortened lifespan. However, it is not uncommon for quality of life to suffer. Affected persons can find their way around in the dark much less easily. This may condition a need for assistance, as the disappearance of sunlight is an everyday phenomenon.Basically, night blindness remains permanent after the first appearance. Most patients then experience neither improvement nor deterioration. Up to now, medicine has had its limits. While a simple defective vision can be corrected without problems by a visual aid, this is not the case with night blindness. If necessary, the night blindness leads to the fact that concerning cannot exercise certain occupations. The outlook is better for congenital stationary night blindness. This form heals in many patients. Similarly, courses in which a vitamin deficiency causes the visual impairment can be successfully treated. On the other hand, people with retinitis pigmentosa have to expect a worsening. Even blindness is possible. Accordingly, the diagnosis of retinitis pigmentosa leads to a differentiated prognosis. While a shortened life expectancy is not foreseeable, there are usually lifelong restrictions in everyday life and occupation. Overall, a mixed outlook can be formulated.
Prevention
Prevention of night blindness is usually impossible. Congenital forms of night blindness, such as a weakness of the rods or retinopathia pigmentosa cannot be prevented. In the case of diabetes, an adapted lifestyle and well-controlled blood sugar often help to prevent damage to the vascular system, including that of the retina. Vegetarians and vegans should make sure to frequently consume vegetables that contain vitamin A, such as peppers, tomatoes, and carrots.
Aftercare
The extent to which follow-up care becomes necessary depends on the chances of recovery. Individuals who have suffered from night blindness since birth, in particular, must cope with the condition for the rest of their lives. There is no prospect of a cure. They have no choice but to seek help from others when it is dark and to avoid dark environments as a matter of principle. Psychological support may be indicated in certain cases. Cases in which night blindness has arisen in the course of life are usually different. Regular checks are then indicated. This is because there is a risk of further deterioration of vision. An annual presentation to the ophthalmologist prevents complications. In addition to a medical history, an eye examination takes place, in which the doctor determines the time it takes for the eyes to adjust to darkness and the perceptible light intensity. From this information and general determinations of visual acuity and visual field, clear comparisons can be made with the past. Necessary treatments can thus be initiated in time. The diagnosis of night blindness entails some requirements for the patient himself. The risk of injury in road traffic should not be underestimated in the case of night blindness.
This is what you can do yourself
If you have night blindness, there are no home remedies available to you. Natural remedies such as bilberry extracts are controversial. The additional intake of vitamin A is also only partially successful. Without a medical diagnosis, self-treatment with alternative methods is strongly discouraged. Reduced vision in poor light causes limitations in everyday life. These must be accepted and managed. Depending on the severity of the symptoms, protective glasses with filters prevent sufferers from feeling blinded by light. However, these glasses do not correct or improve vision. Those who suffer from true night blindness refrain from driving for the sake of themselves and others and resort to public transportation or driving services. Flashlights help with daily journeys in the dark. Ideally, these should have a uniform cone of light to make it easier to see. Digital voice assistants that explain the way via smartphone help with orientation. Self-help groups and associations support those affected. They offer advice on any questions. The exchange with other affected people helps to overcome everyday hurdles. The self-help association Pro Retina specifically targets people with retinal diseases and supports people affected by night blindness.