Mineralization of the trabecular zone in open-angle glaucoma

Relevance In the human body, pathological conditions are often accompanied by ectopic mineralization. The mineral composition of the trabecular meshwork is not reliably known, partly due to the technical difficulty of obtaining and preserving tissue sections [1, 2]. This study is aimed at determining the presence of a bioinorganic component in the drainage zone of the eye in glaucoma [3]. Objective Evaluation of mineralization processes occurring in the anterior chamber of the eye in open-angle glaucoma. Material and methods Using an EVO LS 10 scanning electron microscope (Zeiss, Germany) with an Oxford X-Max-50 energy-dispersive X-ray spectrometer (Oxford, UK), an analysis of the chemical composition of trabecular tissue preparations from 29 patients (30 eyes) aged 73 (58; 78) years with stage II–III open-angle glaucoma, as well as the pigment sheet of the iris obtained from 5 cadaver eyes, was performed. The surface of all samples was visualized in SEM in low vacuum mode (EP, 70 Pa) using a backscattered electron detector (BSE) at an accelerating voltage of 21.5 kV and a sample current of 20–60 pA. Gross chemical microanalysis and micromapping were performed for selected chemical elements: C, N, O, Ca, Cl P, Si, S. Results Significant mineral obliteration of the drainage zone tissue was detected in 7 out of 30 samples: silitization in 3 samples, calcification in 4 samples. The effect of autonomous calcification of pigment granules was revealed: when simulating vital conditions, a mineral phase stoichiometrically corresponding to dicalcium phosphate dihydrate (DCPD) and amorphous calcium phosphate (ACP) was detected on the surface of the granules [4, 5]. Conclusion Calcium and silica obliteration is a potentially significant factor in fluid retention at the trabecular level. Acid-base imbalance in the trabecular region has been identified, contributing to the occurrence of mineral obliteration. Keywords: open-angle glaucoma; biomineralization; scanning electron microscopy