Abstract
The review reflects the current data on unmodified risk factors for cataract development; most prominent are genetic factors and age. Research shows that about half of nuclear and two-thirds of cortical cataracts can be hereditary. Congenital cataracts are hereditary in 25 % of cases, of which 75 % are autosomal dominant. From 30 % to 50 % of congenital cataracts are caused by mutations in genes encoding proteins in the structure of the lens. To date, 115 genes have been identified associated with syndromic and non-syndromic cataracts. Proof of the genetic theory is the development of nuclear cataract in Stickler syndrome (SS), a relatively rare multisystem connective tissue disease inherited in an autosomal dominant manner. The syndrome is characterized by structural abnormalities in collagens of types 2, 9 and 11 and manifests itself in various clinical signs, including the development of facial skeleton anomalies, damage to the vision organ, the musculoskeletal system and the auditory system. Ophthalmic complications of SS are represented by a combination of pathological myopia, retinal detachment, ocular hypertension, early vitreous liquefaction and premature cataract development. Age is the main unmodified risk factor for developing cataracts. The most common form of cataract is age-related nuclear cataract, which in developing countries accounts for 50 % to 90 % of the total number of cases (> 70 versus ≤ 65 years, OR = 12.7). The pathogenesis of age-related nuclear cataract is associated with oxidative damage to proteins under certain conditions: a decrease in the concentration of glutathione (GSH) and vitamin C in the lens nucleus. When examining the frequency of cortical cataract, there was also a relationship with an increase in the age of patients (> 70 years versus ≤ 65 years, OR = 5.96). With age, a barrier is created for the advancement of GSH from the site of its synthesis and regeneration in the cortical layer of the lens towards the nucleus. Numerous experimental and morphological studies confirm the accommodative theory of the development of age-related cortical cataract. Lens deformations caused by accommodation forces lead to heterogeneity of the lens density at the border of the nucleus and cortical layers, an increase in light scattering and damage to the lens fibers. Genetic predisposition and age are interactions of many complex factors that can contribute to the development of cataracts.
Highlights
В настоящее время катаракта стойко лидирует сре‐ ди причин обратимой слепоты — 17,1 млн случаев
Исследования, проведенные в Великобритании, по‐ казывают, что примерно половина ядерной и две трети кортикальной катаракты могут быть обусловлены на‐ следственными факторами [9], при этом доминантные гены вовлечены в процесс развития кортикальной ката‐ ракты, а в патогенезе ядерной катаракты имеют значе‐ ние аддитивные генетические факторы
Эти результаты в целом согласуются с результатами популяционных ис‐ следований [10, 11]
Summary
В настоящее время катаракта стойко лидирует сре‐ ди причин обратимой слепоты — 17,1 млн случаев. Исследования показывают, что от 30 до 50 % врож‐ денной катаракты вызваны мутациями генов, кодирую‐ щих белки в структуре хрусталика, основу которых со‐ ставляют растворимые белки-кристаллины (более 90 %), имеющие большое значение для поддержания показа‐ теля преломления хрусталика В структуре хрусталика человека были идентифицированы три основных клас‐ са «кристаллинов»: α-кристаллин, составляющий 40 %, β-кристаллин — около 35 % и γ-кристаллин — 25 % [12].
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