Pattern-electroretinogram in the differential diagnosis of ocular hypertension and primary open-angle glaucoma

Abstract

PURPOSE. To evaluate the clinical utility of pattern electroretinography (PERG) in the differential diagnosis of ocular hypertension and newly diagnosed primary open-angle glaucoma (POAG) of the initial stage.METHODS. This prospective non-randomized cohort study included patients over the age of 35 years with newly diagnosed ocular hypertension and initial stage POAG in at least one eye. All patients underwent a standard ophthalmological examination, as well as a complex of additional methods used to diagnose POAG: pachymetry, examination of the biomechanical properties of the cornea (Ocular Response Analyzer, Reichert), standard automated perimetry (SAP) (Octopus 900, Haag-Streit Diagnostics), optical coherence tomography (OCT) of the optic nerve head (ONH) and macular area (OCT Triton Plus 3000, Topcon) and PERG (Diopsys Nova, Diopsys, Inc.). Data from both eyes of all included patients were analyzed (12 eyes in the ocular hypertension group and 26 eyes in the POAG group). Statistics was calculated using the StatPlus:mac Software package (StatPlus Inc., Taiwan).RESULTS. During this study we recorded statistically significant differences in steady-state PERG parameters according to the PERG-24 protocol (magnitude, magnitude D — taking into account the magnitude and variability of the response phase throughout the test — and their reverse ratio, determined at pattern contrasts of 100% and 85%) between the groups of patients with newly diagnosed ocular hypertension and newly diagnosed initial stage POAG with a comparable level of intraocular pressure, corneal thickness, biomechanical properties and comparable perimetric indices, as well as the average thickness of the retinal nerve fiber layer and the ganglion cell complex according to OCT data. At the same time, all PERG parameters in the ocular hypertension group were within the normal range, while individual PERG parameters in the POAG group had deviations from the normal.CONCLUSION. Steady-state PERG may be an additional objective method for early detection of disorders in the functioning of retinal ganglion cells (RGCs), which allows differential diagnosis of ocular hypertension without damage of RGCs and initial stage POAG. In addition, dynamic examination with steady-state PERG of individuals with ocular hypertension may allow early detection of the onset of retinal ganglion cells death, i.e. the development of POAG, than with SAP and OCT.