Abstract
Background: Amblyopia related to congenital strabismus belongs to neurological disorders since it is caused by structural and functional remodeling of the visual parts of the brain without any baseline retinal pathology. Although a large number of animal studies on experimentally induced strabismus, as well as clinical cases have been published, the mechanisms and time course of the processes within the brain structures are not fully understood. Aim: To study the time course of abnormalities in the dorsal lateral geniculate nucleus (LGNd) in animals with surgically induced convergent strabismus. LGNd is the structure through which the information from the retina goes to the visual cortex separately for each eye. Materials and methods: 14 strabismic and 17 intact kittens of four age groups were studied. Histochemical method was used to identify cytochrome oxidase which is a mitochondrial respiratory chain enzyme whose activity correlates with neuronal functional activity. Optical density in eye-specific layers A and A1 was measured on the images of stained LGNd sections, with calculation of the contrast difference between them. Results: In strabismic kittens, there were changes in activity of A and A1 layers in the projection of the central part of visual field in LGNd of both hemispheres. At early stages of their formation, a relative decrease in activity was found in both hemispheres in the LGNd layers innervated through non-crossed pathways from both retinae. Thereafter, the time course of abnormalities in LGNd of both hemispheres was different. In the hemisphere ipsilateral to the squinting eye, the difference in layer activity was highest at the age from 3 to 5 months. However, in the opposite hemisphere the same difference indicating a decreased activity in the layer of the squinting eye were observed only at the age of 5 months. Conclusion: The process of amblyopia development during congenital convergent strabismus is characterized by abnormalities in LGNd indicating a possible shift of the visual perception strategy from alternating fixation to suppression of activity of the squinting eye.
Highlights
Amblyopia related to congenital strabismus belongs to neurological disorders since it is caused by structural and functional remodeling of the visual parts of the brain without any baseline retinal pathology
Цель – у животных с хирургически вызванным сходящимся косоглазием исследовать динамику развития нарушений в дорсальном ядре наружного коленчатого тела (НКТд) – структуре, через которую информация из сетчаток поступает в зрительную кору раздельно для каждого из глаз
The process of amblyopia development during congenital convergent strabismus is characterized by abnormalities in LGNd indicating a possible shift of the visual perception strategy from alternating fixation to suppression of activity of the squinting eye
Summary
Исследование проведено на 14 котятах с односторонним сходящимся косоглазием и 17 интактных котятах четырех возрастных групп (таблица). Для увеличения репрезентативности получаемых данных в каждой исследованной области проекции поля зрения оптическую плотность измеряли в среднем в трех близкорасположенных участках НКТд и результаты усредняли. Поскольку изменения наблюдаются в НКТд обоих полушарий, где представлены разные полуполя зрения глаз, при косоглазии нарушено зрительное восприятие в области центральных 10 угл. 2А, Б) в обоих полушариях значения контраста К не отличались от нормы (p > 0,05); у разных животных изменения наблюдались в отдельных, но разных участках проекции поля зрения, что указывает на большую вариабельность оптической плотности в этом возрастном периоде. 2В, Г) в проекции центральной части поля зрения в НКТд обоих полушарий значения контраста К были положительными, что говорит о превышении активности цитохромоксидазы и, соответственно, функциональной активности в слоях А по сравнению со слоями А1. Сведения об экспериментальных животных и срезах дорсального ядра наружного коленчатого тела
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