Describing the Effects of Primary Open Angle Glaucoma on Macula Using Spectral Domain Optical Coherence Tomography in Central India

Abstract

Introduction: Primary open-angle glaucoma is a silent predator of sight, killing retinal ganglion cells (RGCs), and leads to characteristic optic nerve head (ONH) changes and visual field (VF) defects. The conventional methods of diagnosis include clinical examination and perimetry. However, by these at the time of diagnosis, a substantial loss of RGCs has already occurred. Spectral domain optical coherence tomography (SD-OCT) allows quantitative measurements of various parameters of the retina. This tool may be utilized for selective measurement of macular parameters to make an early diagnosis of primary open angle glaucoma (POAG). Methods: In 6 months of study, a total of 81 eyes of 51 subjects underwent SD-OCT measurements, that is, 49 eyes of 35 POAG subjects and 32 eyes of 16 age-matched healthy subjects, to record all measurable macular parameters, namely, macular thickness (MT)-central, average, in all sectors of the inner and outer circle of early treatment of diabetic retinopathy study (ETDRS) macular map; macular volume, ganglion cell-inner plexiform layer (GC-IPL) thickness-in all sectors; succeeded by statistical calculations using the unpaired t-test to calculate two-tailed p-value which is significant when its value is <0.05. Results: As an observation the average MT, MT in the inferior and temporal sector of the inner circle of the ETDRS macular map, that in the inferior sector of the outer circle, minimum GC-IPL thickness, and GC-IPL thickness in all sectors were all significantly reduced in POAG eyes than healthy eyes. Whereas central MT, average GC-IPL thickness, macular volume, and MT in few sectors of the inner and outer circle of the ETDRS macular map proved to bear an insignificant change of POAG. Conclusion: In this study, the greatest impact of POAG on macula was discovered in the GC-IPL layer and MT in the inferior sector of inner and outer ring which might serve the purpose of diagnosis of POAG apart from the established parameters of RNFL and ONH.