Best's disease – one of forms of a bilateral central (makulyarny) pigmentary abiotrophy of a retina leading to dystrophy of photoreceptors of a yellow spot and considerable deterioration in sight. It is characterized by originally asymptomatic current, visual acuity falls over time, there is the central scotoma. Diagnostics is made on the basis of survey of an eye bottom, data of an elektrookulografiya and fluorescent angiography of vessels of a retina, genetic researches. Specific treatment of a disease of Best does not exist, the supporting treatment for delay of progressing of displays of pathology is used.
Best's disease (the central pigmentary abiotrophy, vitelliformny dystrophy of Best) – the genetic disease which is characterized by development of cystous dystrophic changes in area of a yellow spot. It is for the first time described in 1905 by F. Best who studied identical violations of sight at eight relatives and suggested about the hereditary nature of pathology. Best's disease with an identical frequency affects both men, and women, occurrence makes about 3-4:100000. In difference of many other forms of an abiotrophy of a retina Best's disease seldom leads to a total blindness, besides, is characterized by a long multistage current. At initial stages of pathology of violation of sight do not develop, and there are practically no symptoms, changes on a retina quite often happen a casual find at medical examination at the ophthalmologist. In due time appointed supporting therapy can slow down development of a disease of Best considerably.
The reason of dystrophy of a retina which takes place at Best's disease is the mutation of a gene of BEST1 localized on the 11th chromosome. It codes protein , belonging to the class of anion channels of a pigmentary epithelium of a mesh cover of an eye. The pathogenesis of violations at Best's disease is thoroughly not studied – it is found out that at this pathology there is a slow destruction of a pigmentary epithelium in the field of a yellow spot, and properties of a membrane of Bruch change. It is resulted by germination of capillaries in subretinalny space, in a retina substance granules, on the biochemical properties similar with lipofustsiny collect. Macroscopically at Best's disease in the field of a yellow spot pigmentary violations slowly accrue, then there is a cyst which blocks intake of light to the most part of photoreceptors of makulyarny area. Then there is a rupture of a cyst, its contents rezorbirutsya, on its place the hem which is the reason of permanent violations of sight is formed.
The mechanism of inheritance of mutations of a gene BEST1 – autosomno-prepotent with rather high penetrantnost. Besides Best's disease, violation of structure of this gene can be the cause of some other forms of a pigmentary degeneration of a retina, a bestrofinopatiya, vitelliformny dystrophy of adults. The last on the current is very similar to Best's disease, but unlike it develops not at children's, and adult age. It allows to assume that vitelliformny dystrophy of adults is a kind of a syndrome of Best – the modern genetics did not find yet other mutations which would lead to this state.
Symptoms of a disease of Best
The first changes at an eye bottom at Best's disease arise at the age of 2-5 years, however subjective symptoms at the same time are not observed. Therefore the disease is diagnosed or following the results of casual medical examination, or at later age, after development of the first violations of sight. In general Best's disease is characterized by a certain staging.
The zero stage of a disease of Best is diagnosed very seldom as at it there are even no minor changes in area of a yellow spot. Only decrease in a fovealny reflex and change of an elektrookulografiya is observed. When studying the last decrease in coefficient of Arden comes to light. Sometimes such manifestations are registered at adults without further development of a clinical picture of a disease of Best – it is considered BEST1 gene mutation carriage sign.
During the first stage subjective symptoms all are also not expressed, insignificant decrease in visual acuity is only in certain cases observed. At an eye bottom several yellowish points in makulyarny area of a retina come to light. During the second stage of a point expand to the sizes comparable to diameter of a disk of an optic nerve, and are externally similar to an egg yolk. Violations of visual acuity at this stage of a disease of Best do not correspond to an ophthalmologic picture and are insignificant – it remains at the level of 0,6-0,9. At the third stage of a disease of Best there is a rupture of vitelliformny cysts that leads to sharp decrease in visual acuity. Also widespread complaints at this stage are a zatumanivaniye of sight, difficulty with reading the small text. The fourth stage is characterized by a resorption of products of a rupture of cysts and formation on their place of a hem. Visual acuity at different patients at this stage makes from 0,02 to 0,7, besides, there is relative central scotoma and a pseudo-hypopeony. Borders of a field of vision, as a rule, do not change, normal perception of flowers remains.
Duration of each stage at different patients can fluctuate over a wide range. Besides, in certain cases Best's disease can develop more quickly therefore some stages are not diagnosed. Changes on eye day of both eyes most often have asymmetric character. As a rule, the total blindness does not come, can be one of complications of a disease of Best formation of the subretinalny neovascular membrane considerably reducing visual acuity. Besides, with age on the place of hems after vitelliformny cysts development of a horiodalny sclerosis is possible.
Diagnosis of a disease of Best
Diagnosis of a disease of Best is made by means of methods of modern ophthalmology – survey of an eye bottom, an elektrookulografiya, a fluorescent angiography of vessels of a retina. At survey depending on a stage of a disease either yellow points, or the created vitelliformny cysts concentrated in the center come to light. After their gap (the third stage of a disease of Best) the picture of an eye bottom reminds "fried eggs talker". Besides, at any stage of a disease there can be retinalny hemorrhages also noticeable at survey. At the last stage of a disease of Best the pseudo-hypopeony is formed, pigmentary deposits in the field of a yellow spot are noticeable.
One of the very first displays of a disease is the abnormal picture of an elektrookulografiya which is registered even before emergence of the first changes at an eye bottom. The Patognomonichny symptom of a disease of Best – decrease in coefficient of Arden or the relation of light peak to light recession which at final stages of development of pathology does not exceed 1,5. At a fluorescent angiography at the first stages of a disease (before formation of vitelliformny cysts) the sites of local hyper fluorescence corresponding to places of an atrophy of a pigmentary epithelium are observed. After formation of cysts (the second stage of a disease of Best) in places of their localization find total absence of fluorescence, and at their gap (the third stage) – hyper fluorescence in the top parts of cysts and its absence in lower.
By the doctor geneticist also genetic diagnosis of a disease of Best which comes down to a sekvenirovaniye of the sequence of a gene of BEST1 for the purpose of search of mutations can be made. This research belongs to rather difficult as in this area of the 11th chromosome the huge number of genes is located, mutations of many of them are also capable to lead to hereditary ophthalmologic diseases. Differential diagnosis of a disease of Best is carried out with Koats's syndrome and an otsloyka of a pigmentary epithelium. Unlike them the central pigmentary abiotrophy always has bilateral character and is characterized by an abnormal elektrookulografiya.
Treatment and forecast of a disease of Best
Specific treatment of a disease of Best does not exist in this connection use the supporting therapy capable considerably to slow down progressing of pathology. Refer purpose of vitamins A to it and E, the vasodilating and improving to a traffic of a retina means – meldoniya, , ethylmethylhydroxypyridine . It slows down development and the subsequent rupture of vitelliformny cysts, allowing to keep satisfactory visual acuity a long time. When Best's disease was complicated by formation of a subretinalny neovascular membrane, laser correction is shown.
Forecast of a disease of Best, as a rule, conditionally favorable. Total loss of sight occurs seldom or never, usually everything is limited to decrease in visual acuity and relative central scotoma. Peripheral and twilight sight does not suffer, patients are only at a loss further during the work with a small font and fine details. At vitelliformny dystrophy of adults of violation of sight are expressed even more weakly, in some cases patients have no complaints at all, and existence of a disease is defined only by ophthalmologic and genetic researches.