Ganglion Cell Complex thickness as an early predictor of microstructural changes in varying degrees of myopia in comparison with Retinal Nerve (Fiber Layer (RNFL) thickness)

Purpose: To compare the Ganglion Cell Complex (GCC) thickness with Retinal Nerve Fiber Layer (RNFL) thickness in correlation with visual field (VF) in varying degrees of myopia. Design: a Cross-Sectional study. Participants: Ninety-six eyes of 49 patients with myopia. Methods: Patients with myopia examined with streak retinoscope to obtained the best corrected visual acuity based on spherical equivalent. Patients then divided into low (50 eyes=50.1%), moderate (31 eyes=32.3%), and high (15=15.6%) myopia. Axial length measured with A-Scan ultrasound divided into short (4=4.2%), moderate (74=77.1%), and long (18=18.7%). SD-OCT was used to measured GCC thickness in 9 areas including fovea (R1), parafovea (R2-R5), and perifovea (R6-R9) according to early treatment diabetic retinopathy study (ETDRS), and RNFL thickness in five areas (G,TS, TI, NS, N, NI). VF analysis with Humphrey field analyzer with SITA 24-2 pattern. Main outcome measures: GCC thickness has higher correlation with degree of myopia particularly in perifovea area and means deviation than RNFL thickness. Results: GCC thickness decreased significantly along with the elevation of myopia degree in almost entire area except R1 and R5. Para fovea (R2-R4) and perifovea (R6-R9) were significantly correlated with p= 0.001,0.005,0.006 and p= 0.000,0.000,0.000, and 0.003 respectively. In contrast, RNFL thickness obtained lower correlation with myopia degree whereas the only significant result was found in Nasal area (p= 0.045). VF found to be strongly correlated with the degree of myopia in which p-value for Mean Deviation = 0.000. Conclusions: GCC thickness may compare the predictive value of RNFL in predicting early retinal microstructural changes even in low degree myopia.