Atypical forms of pigment retinitis
Other forms of pigment retinitis include pigmented inverted retinitis (central form), pigmentary retinitis without pigment, pigmentary pigment retinitis and pseudopigment retinitis. Each of these forms has a characteristic ophthalmoscopic picture and an electroretinographic symptomatology.
- Sectoral retinitis pigmentosa is characterized by changes in the water quadrant (usually nasal) or half (more often in the lower quadrant). Progresses slowly or does not progress at all.
- Pericentral pigmentary retinitis, in which the pigmentation spreads from the optic nerve disc and passes to the temporal arcades and nasally.
- Retinitis pigmentosa with exudative vasculopathy is characterized by a similar to Coats disease ophthalmoscopic picture with lipid deposits in the peripheral retina and exudative retinal detachment.
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Pigmented inverted retinitis (central form)
Unlike the typical form of retinitis pigmentosa, the disease begins in the macular area and the lesions of the cone system are more significant than the rod-shaped system. First of all, the central and color vision decreases, and photophobia (photophobia) appears. In the macular area, characteristic pigment changes are noted, which can be combined with dystrophic changes at the periphery. In such cases, one of the main symptoms is the lack of day vision. In the field of vision of the central scotoma, the ERG significantly reduced the cone components compared to rod-shaped components.
Pigment retinitis without pigment
The name is due to the absence of pigmental deposits typical for pigment retinitis in the form of bony corpuscles in the presence of symptoms similar to manifestations of retinitis pigmentosa and an unregistered ERG.
Pure retinitis pigmentosa
A characteristic ophthalmoscopic feature is multiple white spot spots throughout the eye fundus with accompanying pigment changes ("moth-eaten tissue") or without them. Functional symptoms are similar to manifestations of retinitis pigmentosa. The disease must be differentiated from a stationary congenital night blindness and a white-spot eye fundus (fundus albipunctatus).
Pseudopigment retinitis is a non-hereditary disease. The cause of its occurrence may be inflammatory processes in the retina and choroid, the side effect of medications (thioridazine, melliril, chloroquine, deferoxamine, clofazamine, etc.), the state after trauma, retinal detachment, etc. On the fundus, changes similar to those with retinitis pigmentosa. The main distinguishing symptom is a normal or slightly decreased ERG. With this form, there is never an unregistered or sharply reduced ERG.
Currently, there is no pathogenetically substantiated treatment of retinitis pigmentosa. Substitution or stimulation therapy is ineffective. Patients with pigment retinitis are recommended to wear dark goggles to prevent damage to light, select the maximum spectacle correction of visual acuity, prescribe symptomatic treatment: for macular edema, systemic and topical use of diuretics (inhibitors of carbonic anhydrase), for example, diacarb, diamox (acetazolamide); in the presence of lens opacities, surgical treatment of cataracts for improvement of visual acuity, in the presence of neovascularization for the prevention of complications, photocoagulation of vessels, prescribe vascular drugs. Patients, their relatives and children should undergo genetic counseling, research of other organs and systems to avoid syndrome lesions and other diseases.
Identification of the pathological gene and its mutations is the basis for understanding the pathogenesis of the disease, predicting the course of the process and searching for ways of rational therapy.
At present, attempts are being made in the experiment to transplant pigment epithelial cells and retinal neuronal cells from a weekly embryo. A new promising approach to the treatment of retinitis pigmentosa is associated with gene therapy based on subretinal adenovirus administration, with the contents of healthy minichromosomes within the capsule. Scientists suggest that viruses, penetrating the cells of pigment epithelium, contribute to the replacement of mutated genes.
Generalized hereditary retinal dystrophy associated with systemic diseases and metabolic disorders
There are many systemic disorders that are combined with atypical forms of retinitis pigmentosa. To date, there are about 100 diseases with various eye disorders, caused by a violation of the metabolism of lipids, carbohydrates, proteins. The lack of intracellular enzymes leads to gene mutations, which determines a different genetic pathology, including the disappearance or dystrophy of photoreceptor cells.
Specific systemic diseases, combined with retinitis pigmentosa, include metabolic disorders of carbohydrates (mucopolysaccharidosis), lipids (mucolipidosis, fucosidosis, seroid lipofuscinosis), lipoproteins and proteins, central nervous system damage, Usher syndromes, Lawrence-Muna-Barde-Biddle syndrome, etc.