RESEARCH OF THE BIOMECHANICAL PROPERTIES OF THE CORNEA AND ACCOMODATION IN CHILDREN WITH HYPERMETROPY
About the author:
Shargorodska I. V., Danilenko O. S.
CLINICAL AND EXPERIMENTAL MEDICINE
Type of article:
Hypermetropia is the predominant clinical refraction of childhood, in which accommodation plays a particularly important role. The determination of changes in the biomechanical properties of the capsule of the eye with hyperopia in children presents significant difficulties. To date, in literature the fact of weakening of accommodative ability in children with hyperopia has not found a sufficiently convincing explanation. The study and analysis of the function of accommodation, depending on the variability of the optical apparatus of the eye with hyperopia, is of great clinical importance. Aim: to study the biomechanical properties of the cornea and accommodation in children with hypermetropia. Object and methods. The 65 patients (130 eyes) with hypermetropic and emmetropic refraction were included in investigation. In the control group were included 19 patients (38 eyes) with emmetropic refraction. The basic group consisted of 46 patients (92 eyes) with hypermetropia. Initially, patients in both groups were subjected to an initial standard ophthalmic examination. Determination of keratotographic indices was performed in the classical version using the Schampflug camera of Oculus Pentacam. To calculate the biomechanical indices of the cornea, measurements were obtained using a known method and apparatus for assessing the rigidity of the cornea in vivo. A method for assessing the stiffness of the cornea in vivo was performed at Oculus Pentacam using standard device-free, intraocular pressure (IOP) conditions, which was implemented using a rigidity-sensing device horn of the eye in vivo creating uniform metered compression of the eye. At the end of the study carried out the calculation of the ∆SE and the coefficient of corneal rigidity (KER). To describe changes in the corneal biomechanical properties in vivo, a formula was used to estimate the corneal stiffness coefficient. To determine the relative and absolute accommodation used “accommodation test”. Studies of the reserves of absolute accommodation were carried out according to the Dashevsky method. For patients of both groups, the provision for distance accommodation (RA) and the positive part of relative accommodation (PCVA) were determined. The results are showed that analysis of these indicators allows to establish the fact of a probable difference in the sizes of hypermetropic eyes with different accommodation. Hypermetropic eyes, which had weaker accommodation, were larger in size than eyes that had better accommodation (p<0.05). This fact indicates the extension of the capsule of the eyeball. However, the increase in axial length of the eye was not reflected in the degree of hypermetropia. Because the extension of the eye was accompanied by an increase in the radius of curvature of the anterior surface of the cornea and the weakening of its refractive force. The results of the study showed that under conditions of artificially elevated intraocular pressure, the use of a method and device for assessing corneal rigidity reveals the presence of biomechanical disorders of the cornea of patients with hypermetropia and different accommodative capacity compared with control emetropic. The corneal stiffness factor in all the studied cases showed statistically significant results that were consistent with the clinical course of the process in these eyes. Conclusion. The accommodation function is related to the anatomical-optical and biomechanical features of the hypermetropic eyes and correlates with the size of their fibrous capsule and the corneal stiffness factor. It is established that in the hypermetropic eyes, which are characterized by an increase in the curvature of their refractive media, a significant decrease in the axial size, a low coefficient of rigidity of the cornea, a normal accommodation function takes place. With the increase of the size of the eye, especially in its anterior part, the increase of the corneal stiffness coefficient, the refraction of its refractive media decreases, which is accompanied by a decrease in accommodation capacity.
cornea, accommodation, biomechanical properties, rigidity, the coefficient of corneal rigidity, eyes tunica fibrosa, hypermetropia.
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Publication of the article:
«Bulletin of problems biology and medicine» Issue 1 (155), 2020 year, 211-215 pages, index UDK 617.726:617.753.2-072