Cone-rod dystrophy

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Classification according to ICD-10
H35.5 Hereditary retinal dystrophy
ICD-10 online (WHO version 2019)

The cone-rod dystrophies (ZSD) are a heterogeneous group of inherited eye diseases, which are at the beginning of the death of the pin comes in the central retina and then slowly in the outer area and on the sticks spread, as opposed to retinitis pigmentosa which is developing in the opposite direction. If only the cones are affected, cone dystrophies are also used.

Epidemiology

The frequency of cone-rod dystrophies is about 1 in 40,000. They appear most frequently up to the age of 20, but can also only become noticeable later.

The disease can also occur in the context of syndromes such as Jalili syndrome .

Symptoms

Fundus of a 36-year-old patient with CSD

CSD is a disease in which there is a severe loss of visual acuity right from the start and which progresses at variable speed in the further course. The name (cone-rod dystrophy) already gives some information about the disease. When forming a name, the cones are named first, as they are most affected in this clinical picture. They have their highest density in the visual center ( macula ), so that central visual field deficits can already occur at the onset of the disease , which make it impossible for the person concerned to see targeted objects. Since the point of sharpest vision is lost, the eyes are often trembling ( nystagmus ) or the eyes are misaligned ( strabismus ). The increasing loss of the cones leads to disturbances in the adaptation to different light conditions, thus to an increased sensitivity to glare, which significantly impairs vision in bright light. The recognition of colors is also disturbed early on. Since the rods are hardly affected at the beginning of the disease, vision is still possible at dusk. It is only later that the middle and outer areas of the retina and thus the rods are also affected.

genetics

The term dystrophy , which is at the end of the name, indicates that this disease is a congenital, slowly progressive destruction of tissue. This is due to mutations in various genes.

Inheritance is autosomal recessive in most cases . However, there is also an autosomal dominant or x-linked inheritance . These mutations lead to disturbances in signal transmission and to changes in the structure and function of the cones. In other cases the visual purple may not be formed or the transport of substances through the cell membrane may be disrupted. In a relatively large number of CSD sufferers, mutations were localized in the ABCA4 gene, which is responsible for coding a transport protein in the vitamin A metabolism. Therefore, the intake of high doses of vitamin A cannot be recommended for these sufferers.

Diagnosis

At the beginning of the disease, the fundus is often inconspicuous and pigment changes in the macula area only become visible in the further course. In the early stages of the disease, therefore, a reliable diagnosis can often only be made with an electroretinogram (ERG). Furthermore, dark brown to black metabolic deposits (bones) and vascular constrictions can form. There is also a loss (atrophy) of the pigment epithelium and the choroid, which are important for the nutrition of the visual cells. This can lead to the fact that the pigment epithelial layer is no longer present in the center of the retina. The strong color of the optic nerve head can also fade as the disease progresses (papillae fading), which can indicate a loss of function of the optic nerve.

Treatment approaches

In addition to a healthy lifestyle, wearing sun protection glasses can have a positive influence on the course of the disease. Edge filter glasses are recommended for this, which should not only filter out the UV radiation, but also the blue light component. In addition, according to individual selection, it can also achieve a contrast improvement.

literature

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