Functional and anatomical assessment of retinal ganglion cells in glaucoma

Abstract

Purpose The aim of the study was to assess the ability of retinal ganglion cell (RGC) complex measurements obtained by optical coherence tomography (OCT) to detect glaucoma, to measure RGC loss by pattern electroretinogram (PERG), and to correlate the results of PERG with OCT for glaucoma detection. Patients and methods Fifty glaucoma suspects (100 eyes), 70 glaucoma patients (140 eyes), and 50 age-matched controls (100 eyes) were examined. Participants had clear ocular media, no or mild refractive errors, and no concomitant ocular or systemic diseases. Superior and inferior ganglion cell complex thickness and retinal nerve fiber layer (RNFL) thickness were measured by means of OCT. The amplitude and latency of PERG were elicited by counter-phase checks. Results The mean RNFL thickness and mean RGC thickness were reduced in glaucoma patients compared with glaucoma suspects and controls. The mean RNFL thickness was 88 ± 9.9 µm in early glaucoma, 94 ± 12 µm in glaucoma suspects, and 99 ± 15.5 µm in controls. The total RGC thickness was 55 ± 6.2 µm in early glaucoma, 64.9 ± 3.8 µm in glaucoma suspects, and 65 ± 4.1 µm in controls. The mean PERG amplitude was decreased in both glaucoma suspects and glaucoma patients compared with controls. In glaucoma suspects, PERG amplitude did not correlate significantly with both RNFL thickness and RGC thickness, whereas in glaucoma patients PERG amplitude was positively correlated with both RNFL and RGC thickness. Conclusion OCT can assess the RGC anatomically, whereas PERG can functionally evaluate RGC loss. Lack of anatomical–functional relationship in glaucoma suspects suggests that at this stage PERG losses appear to affect primarily the retinal/optic nerve function. In glaucoma patients, PERG reflects both dysfunction and loss of ganglion cells.