Dynamic Biometric Indicators of the Anterior Segment Structure of the Eye in Primary Angle-Closure Glaucoma

Abstract

Introduction. Primary angle-closure glaucoma (PACG) remains one of the leading causes of irreversible blindness. Up to date, a significant amount of data has been accumulated concerning the biometric parameters of the eye in PACG, however, there is a lack of information on the dynamic characteristics of these parameters.Objective: to evaluate the dynamic biometric characteristics of the structures of the anterior segment of the eye in PACG.Patients and methods. The results of optical coherence tomography were analyzed in 40 patients with PACG and in 40 patients without signs of hydrodynamic disorder. The studies were carried out under photopic and mesopic illumination conditions. The scanned images were obtained using an RTVue-100-2 optical coherence tomograph device (Optovue, USA). Biometric measurements were performed using standard tomograph software; volumetric studies were carried out based on the Pappus-Guldinus theorem with additional constructions. When analyzing the obtained images, 13 different linear and volumetric parameters were evaluated.Results. A decrease in the parameters reflecting the features of the configuration of the anterior chamber of the eye was noted in the presence of PACG (width of the ACA, depth and volume of the anterior chamber). From the point of view of the possible influence on the state of the anterior chamber angle, it is necessary to highlight changes in such indicators as the area, volume and thickness of the iris. Regardless of the conditions of the examination, these indicators, on average, were significantly higher in the PACG and practically did not change with a decrease in the level of illumination. At the same time, in the absence of disturbances in hydrodynamics under mesopic conditions, despite an increase in the thickness of the iris, a significant decrease in its area and volume was noted.Conclusion. Biometric changes in the structures of the anterior segment of the eye in the case of PACG relate not only to linear, but also to volumetric indicators. As a certain component of hydrodynamic disorders in the case of PACG, the revealed preservation of the iris volume during pupil dilation under mesopic illumination conditions should be considered, while in the absence of hydrodynamic disorders, this indicator decreased. Therefore, not only static changes in the biometric characteristics of the structures of the anterior segment of the eye, but also their dynamic fluctuations, should be considered as a risk factor for clinical manifestations of PACG, which determines the practical significance of dynamic biometric studies in the examination of patients with suspected PACG.