Bradyopsia, which stands for “slow vision,” is an eye condition that affects vision. The eyes of patients with bradyopsia adapt more slowly to changing light conditions, causing them to be blind for a few seconds. The condition is often congenital, but sometimes it is also acquired. The extremely rare condition is hereditary and quite stable in nature. However, this can have serious consequences for the patient and he must always take this into account, both indoors and outdoors.
- Epidemiology bradyopsia
- Causes and heredity of the condition
- Mutations
- Mode of inheritance
- Symptoms: Slower response to changing light intensities and photophobia
- Diagnosis by the ophthalmologist
- Eye disease treatment
- Progression of eye disease
Epidemiology bradyopsia
Only a handful of affected patients worldwide have been reported in the medical literature. Information regarding gender preference, geographical features, etc. have not been reported. The prevalence is therefore <1/1 000 000.
Causes and heredity of the condition
Mutations
The cause of the condition is mutations (medical term for “alterations”) in either the RGS9 or RGS9BP gene. Their production takes place in the retina; the tissue at the back of the eye that detects light via photoreceptors. The pigments in photoreceptors receive stimulation when light enters the eye. This causes a series of chemical reactions that produce an electrical signal. The brain then interprets that as vision. The mutation of the RGS9 or RGS9BP gene prevents photoreceptors from recovering quickly after a response to light. With normal vision, the photoreceptors return to their resting state in a fraction of a second after exposure to light. In patients with bradyopsia where there are mutations in one of these genes, this takes ten seconds or even longer. The photoreceptors are unable to respond to light during that time. This delay causes temporary blindness in response to changing lighting conditions and also interferes with seeing small moving objects .
Mode of inheritance
Bradyopsia is autosomal recessive , meaning both copies of the mutated gene must be present in each cell for the condition to be expressed. The parents of a patient with an autosomal recessive disorder each carry one copy of the mutated gene, but usually do not show the symptoms of the condition.
A number of patients have an unknown cause of bradyopia; no mutations can be found in the RGS9 or RGS9BP gene. Perhaps a tumor is the cause, but further research is needed.
Symptoms: Slower response to changing light intensities and photophobia
Vision problems usually occur in childhood or during puberty. Patients with this condition are blind for five to ten seconds when they move from a dark to a light environment. In addition, it is also difficult for these patients to go from a (brightly) lit to a darkened room, for example when driving through a dark tunnel on a sunny day. So they also suffer from photophobia (aversion to light).
A number of patients also have difficulty seeing moving objects. This is especially the case with small objects that move against a light background, which can be seen, for example, during ball games. Another possible symptom is a reduction in visual acuity, although this also depends on the individual and is often also associated with the lighting of the examination conditions.
Diagnosis by the ophthalmologist
The ophthalmologist performs an ophthalmological examination and has an ERG performed on a patient. Here he clearly identifies the slower response to lighting conditions.
Eye disease treatment
There is no proven effective treatment for the congenital form of bradyopsia. The treatment of the acquired type of bradyopsia is aimed at curing the underlying condition(s). The treatment is mainly supportive .
Progression of eye disease
Patients often have to adapt and sometimes find this annoying. For example, patients may avoid very bright or dark spaces to prevent temporary blindness. Some sports are also not possible, such as tennis and football. Watching these sports can also be very difficult for these patients. Dark sunglasses may provide them with relief. The condition is
stable in most cases . Some patients develop amblyopia, but scientific studies appear to indicate that this is not related to the condition. A patient should also visit the ophthalmologist annually for a comprehensive eye examination and an ERG (electroretinography).
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