Intereye asymmetry of optic nerve head parameters and retinal nerve fibre layer thickness in patients with open angle glaucoma detected by spectral domain optical coherence tomography

Abstract

INTRODUCTION. The aim of the study is to evaluate intereye asymmetry of optic nerve head (ONH) parameters and the circumpapillary retinal nerve fibre layer (cpRNFL) thickness in patients with primary open angle glaucoma (POAG). MATERIA LS AND METHODS. The study included 44 patients with POAG in both eyes, 48 binocular glaucoma suspects, and 75 individuals with two healthy eyes. A mixed group of 20 patients had only one eye that met the criteria for POAG. We evaluated the differences between right and left eyes and absolute intereye asymmetry for the individual ONH parameters and cpRNFL thickness, measured by spectral domain optical coherence tomography (SdOCT). RESULTS. The comparison of average values of the ONH parameters between the right and left eyes in the group of healthy subjects showed no significant differences apart from the significantly higher rim volume (RV) in the right eye. In addition, the cpRNFL was an average of 4.23 μm thicker in the right eye than in the left eye in healthy subjects. The absolute difference of ONH parameters between the eyes of patients with POAG was higher than in healthy patients for most parameters, but statistical significance was only reached for cup volume (CV). The asymmetry of the cpRNFL thickness increased in patients with glaucoma compared with healthy subjects. The absolute asymmetry of the average cpRNFL thickness in all quadrants was 12.07 μm in patients with glaucoma versus 6.56 μm in healthy subjects (p < 0.05). In the group of glaucoma suspects, cpRNFL intereye asymmetry decreased in almost all parameters in comparison to healthy patients with statistical significance for superior and inferior quadrant. CONCLUSIONS. In patients with POAG, the intereye asymmetry increases for ONH and cpRNFL parameters compared with healthy eyes; however, statistically significant differences were only found for the cup volume and cpRNFL thickness average for all quadrants. The onset of glaucoma is associated with a reduction of the physiologically occurring asymmetry that results from greater cpRNFL thickness in the right eye.