Optical coherence tomographic findings in optic nerve hypoplasia
A 67-year-old woman presented with blurring of the left eye. The patient presented with best-corrected visual acuity of count fingers at 2’ oculus dexter (OD) and 20/40 oculus sinister (OS). A relative afferent pupillary defect was observed in the right eye. There were nuclear sclerosis (Lens Opacities Classification System (LOCS) III grading = 1) in both eyes. A small optic disc and double ring sign were observed in the right eye and left was normal.\nIn order to evaluate the thickness of each layers of retina, OCT imaging was performed for both eyes. 5-line Raster scan, which makes five line scans with 6 mm width in horizontal and each separated by 250 μm, and optic disc cube scan were generated. We selected the results with minimum signal strength seven and the third row of the five line scans that passed the fovea to compare both eyes.\nTo compare and analyze each layers of the retina, 21-points of each Raster scans were selected using the caliper tool in the device. Each points were located at 250; 500; 750; 1,000; 1,250; 1,500; 1750; 2,000; 2,250; and 2500 μm apart from the fovea to nasal and to temporal side.\nOur OCT device did not provide thickness maps of each layers of retina, which was the main concern in this study. Therefore, for quantitative analysis of retinal layers, segmentations were done to three parts, which were RNFL, inner retinal layer (IRL), and ORL; on the basis of internal limiting membrane, posterior boundary of the RNFL, posterior boundary of the outer plexiform layer, and anterior boundary of the cone outer segment tip line.[] RNFL thickness (RNFLT), IRL thickness (IRLT), and ORL thickness (ORLT) were measured manually using the caliper tool in the device. The Wilcoxon's signed-rank test and t-test were used for the comparison of RNFLT, IRLT, and ORLT; between both eyes. Statistical analysis was performed using SPSS®, version 14.0 (SPSS Inc., Chicago, IL). The results were considered significant at P < 0.05.\nThe average of RNFLT of ONH was thinner than the opposite eye [] and the thickness analysis of each five line scans were represented by a graph and fundus photograph map, respectively []. RNFLT and IRLT of ONH were significantly thinner than the opposite eye, for all five lines (P < 0.05). However, ORLT did not show significant difference between both eyes for all five lines (P > 0.05). In addition, to compare the thickness of retinal layers of the nasal and temporal areas from the fovea, each 50 points from the fovea to the nasal and temporal sides were divided into two groups. The results were the same as above. RNFLT and IRLT of the right eye were significantly thinner than the left eye on the temporal and nasal side (P < 0.000), but ORLT did not show significant difference between both eyes (P = 0.879, 0.164). The differences of RNFLT and IRLT between both eyes are greater on the nasal side than the temporal side as shown in (difference of RNFLT between both eyes on the temporal and nasal side: 2.04 vs 9.02 μm, IRLT: 20.86 vs 45.02 μm).