Changes in target IOP values in glaucoma patients depending on the number of surgical interventions they underwent

Abstract

PURPOSE. To determine the optimal intraocular pressure (IOP) values that contribute to stabilization of the course of the disease in patients with different stages of primary open-angle glaucoma (POAG) before and after surgery, depending on the current state of ocular biomechanical parameters.METHODS. This analytical descriptive scientific-clinical study analyzes the results of diagnostic studies conducted in the period from 2019 to 2022. The final protocol included 137 patients (209 eyes) with different stages of POAG. Two groups of patients were identified: the main group (105 patients, 156 eyes) with POAG, and the control group (32 patients, 53 eyes) — healthy individuals and patients with an established diagnosis of cataract. All patients underwent a thorough ophthalmological examination, including routine as well as special methods such as ophthalmotonometry in six different ways, bi-directional pneumatic applanation of the cornea, measurement of central corneal thickness (CCT). Additional decrease of the IOP level depending on the characteristics of the fibrous membrane of the eye was calculated using a simple regression followed by an assessment of the quality of the constructed model according to the calculated coefficients of determination (r2).RESULTS. The IOP values and biomechanical parameters of the fibrous membrane of the eye were analyzed depending on the stage of glaucoma process and the absence or presence of a history of surgical interventions for glaucoma in patient’s anamnesis. Significant differences in the viscoelastic parameters of the fibrous membrane of the eye were revealed between patients who had not undergone surgical treatment and those who had undergone one or two surgeries. Algorithms were developed to determine specific correction coefficients in order to correctly interpret the results of tonometry, taking into account the biomechanical characteristics of the membranes of the eye, and differences in target IOP were determined for groups of patients with different stages of POAG before and after surgical treatment.CONCLUSION. The results of this study demonstrate that the changing characteristics of the fibrous membrane of the eye in patients with glaucoma associated with previous surgical treatment can significantly distort the interpretation of data obtained using the basic ophthalmic tonometry. The study also shows that when choosing a «safe» range of IOP levels in patients with POAG, it is necessary to take into account patient’s history of penetrating surgical interventions. Thus, in single-operated patients, an additional decrease in IOP is required, on average by 1.7 mm Hg, while in repeatedly operated patients — by almost 3 mm Hg.