Factors associated with topographic changes of the optic nerve head induced by acute intraocular pressure reduction in glaucoma patients

Abstract

To investigate factors associated with changes in optic nerve head (ONH) topography after acute intraocular pressure (IOP) reduction in patients with primary open-angle glaucoma (POAG). Untreated POAG patients (IOP >21 mm Hg) were prospectively enrolled. Systemic and ocular information were collected, including central corneal thickness (CCT) and corneal hysteresis (CH). All patients underwent confocal scanning laser ophthalmoscopy and tonometry (Goldmann) before and 1 h after pharmacological IOP reduction. The mean of three measurements was considered for analysis. Changes in each ONH topographic parameter were assessed (one eye was randomly selected), and those that changed significantly were correlated with patient's systemic and ocular characteristics. A total of 42 patients were included (mean age, 66.7 ± 11.8 years). After a mean IOP reduction of 47.3 ± 11.9%, significant changes were observed in cup area and volume, and in rim area and volume (P < 0.01), but not in mean cup depth (P = 0.80). Multiple regression analysis (controlling for baseline IOP and magnitude of IOP reduction) showed that CH (r(2) = 0.17, P < 0.01) and diabetes diagnosis (r(2) ≥ 0.21, P < 0.01) were negatively correlated with the magnitude of changes in ONH parameters, whereas the cup-to-disc ratio was positively correlated (r(2) = 0.30, P < 0.01). Age, race, disc area, and CCT were not significant (P ≥ 0.12). Including all significant factors in a multivariable model, only the presence of diabetes remained significantly associated with all ONH parameters evaluated (P < 0.01). Different systemic and ocular factors, such as diabetes, CH, and the relative size of the cup, seem to be associated with the magnitude of changes in ONH topography after acute IOP reduction in POAG patients. These associations partially explain the ONH changes observed in these patients and suggest that other factors are possibly implicated in an individual susceptibility to IOP.