Abstract
Purpose: :
In the presence of myopic tilted disc and peripapillary atrophy(PPA), retinal nerve fiber layer thickness measurement with OCT could have difficulty in determining the optic disc margin, and inappropriate location of OCT scan circle might induce unreliable results.The purpose of this study was to investigate the influence of new OCT scan circle location on the profile of peripapillary RNFL thickness in healthy myopic eyes with tilted disc and PPA.
Methods: :
Among four hundred ninety two eyes of 252 healthy young myopic male volunteers, 69 eyes of 38 subjects who have a myopic tilted disc and temporal PPA were enrolled. In all eyes, RNFL thickness analysis with Cirrus HD-OCT were performed. At first, RNFL thickness was sampled along a 3.4-mm-diameter circle centered on the disc margins determined automatically by a Carl Zeiss Meditec ONH analysis algorithm developed for Cirrus HD-OCT (method 1). After that, we manually placed the scan circle to new location centered on the margin involving the temporal edge of the PPA and nasal scleral ring which corresponded to termination of retinal pigment epithelium (method 2). Average, sectorial peripapillary RNFL thickness profile and mean number of abnormal clock-hour sectors at P<5% level was compared between two methods
Results: :
Mean age of 69 eyes with tilted disc and PPA was 21.5±1.68. Mean spherical equivalent was -4.70±2.52D and mean axial length was 25.76 ±1.17mm. In comparison with method 1 and 2, no statistically significant differences of the global average thickness (P=0.109). For quadrant measures, the RNFL thickness of method 2 was significantly thicker in the superior(P=.032), inferior(P<.05), nasal(P=.06) quadrant, and thinner in the temporal(P<.05) quadrant than method 1. Mean number of abnormal clock-hour sectors at P<5% level was significantly decreased in method 2 (1.42) compared to method 1 (0.84) (P<.05).
Conclusions: :
In the presence of myopic tilted disc and PPA, peripapillary RNFL thickness measurement with manually positioned OCT scan circle centered on the termination of RPE was more about normative database of Cirrus HD-OCT than with automatically determined scan circle.
Keywords: imaging/image analysis: clinical • myopia • nerve fiber layer