[The relationship between intraocular pressure and age-related variations in ocular rigidity]. / Vzaimosvyaz' vnutriglaznogo davleniya s involyutsionnymi kolebaniyami rigidnosti glaza.

PURPOSE: This study aimed to identify the correlation between age-related fluctuations in the average values of rigidity of the fibrous tunic of the eye (FTE) and corresponding ranges of true intraocular pressure (IOP) in healthy eyes and eyes with open-angle glaucoma (OAG); using the identified ranges of FTE rigidity, to establish the appropriate IOP zones for healthy and glaucomatous eyes, taking into account the aging periods as classified by the World Health Organization (WHO). MATERIAL AND METHODS: Ocular-Response Analyzer tonometry was used according to the Koshits-Svetlova dynamic diagnostic method to examine 674 patients with healthy eyes and 518 patients with glaucomatous eyes, aged 18 to 90 years, classified according to the WHO aging periods, and a theoretical analysis was conducted to estimate clinical values of FTE rigidity, the current level of true IOP, and the calculated individual IOP level in a patient's eye during youth. RESULTS: The following IOP level zones were identified for patients with healthy and glaucomatous eyes: low IOP zone (≤13 mm Hg); medium IOP zone (14-20 mm Hg); elevated IOP zone (21-26 mm Hg); high IOP zone (27-32 mm Hg); subcompensated IOP zone (33-39 mm Hg); and decompensated IOP zone (≥40 mm Hg). CONCLUSION: The fundamental physiological criterion "rigidity" does not depend on central corneal thickness and consistently reflects the current level of true IOP. In all examined patients, both with healthy and glaucomatous eyes, healthy and glaucoma eyes with the same level of current rigidity had the same level of IOP. The ability to assign a given healthy or glaucomatous eye to a specific individual IOP zone is particularly important for the polyclinic system.

[Morpho-physiological features of the human eye sclera as the key unit in the level of intraocular pressure under normal conditions and in glaucoma].

The results of sclera investigations from the positions of morphology, physiology, biomechanics and control-system theory, are summarized. The morphological evidence was obtained supporting the physiological hypothesis stating that the specific anatomical organization and spatial displacement of elastic fiber-containing scleral layers against one another, are the key elements in formation of the individual level of intraocular pressure (IOP) in man both under normal and pathological conditions. It was shown that the elastic fibers outlined the collagen lamallae in of scleral internal layers. External scleral layer lacked elastic fibers. Scleral elastic fibers are necessary for the functioning of the mechanism of sclera microfluctuations associated with the intraocular fluid accumulation and removal, they are also important for dampening the sudden changes of IOP. Under normal conditions, age-related increase in scleral rigidity is primarily associated with the process of accelerated aging of its superficial non-elastic layers, resulting in the physiological response of the current IOP level elevation. As IOP becomes elevated under normal conditions, the internal elastic fiber-containing scleral layers are increasingly pressed against more rigid external layer. This limits the displacement capacity of internal layers against each other, resulting in the decline of the efficiency of elastic fiber work in dampening the sudden changes of IOP. In the healthy eyes, the process of scleral aging brings to a natural development of ophthalmohypertension, when IOP elevation is physiologically required for the maintenance of the volume microfluctuation mechanism ("scleral respiration"). In glaucoma, the pathological rearrangement of the scleral fibrous structures is observed, resulting in an additional abrupt increase of its rigidity, with the reciprocal significant elevation of the current level of IOP and the amplitude of its jumps. Pathophysiological mechanism of these significant changes in glaucoma remains currently unknown, however, morphological evidence indicates that it is associated with the changes in the metabolic processes in sclera.

[Morpho-functional characteristics of lens ciliary body as a key mechanism of accommodation in human eye]. / Morfologicheskie i funktsional'nye osobennosti resnichnogo poiaska khrustalika kak kliuchevogo ispolnitel'nogo zvena v mekhanizme akkommodatsii glaza cheloveka.

With the aid of ophthalmological, morphological, biomechanical and regulation theory methods the inconsistency of prevalent concepts on the functional interpretation of morphological structure of ciliary zonule was demonstrated and the scheme of functioning of its elements matching clinical and physiological observations was proposed. The role of anterior and posterior portions of ciliary zonule appears to be functionally essential and consistent with accommodation mechanism proposed by Helmholtz, while the role of cilioequatorial fibers of ciliary zonule is functionally auxiliary. Morphological and constructive peculiarities of ciliary zonule structure confirm the validity of Helmholtz concepts of accommodation mechanism.