The circumpapillary retinal nerve fiber layer thickness and optic disc parameters in retinitis pigmentosa eyes

Objective To observe the changes of circumpapillary retinal nerve fiber layer (CP-RNFL) thickness and optic disk parameters in retinitis pigmentosa (RP) eyes. Methods Prospective clinical case-control study. A total of 25 patients (42 eyes) with RP were in the RP group, and 42 age matched healthy subjects (84 eyes) in the control group. All subjects underwent optical coherence tomography (OCT) examination, in which 37 eyes with 3D optic disk scanning and 5 eyes with circle optic disk scanning. The parameters included average thickness of entire CP-RNFL, thickness of nasal, superior, temporal and inferior quadrant of CP-RNFL, disc area, disc cup area, rim area, cup/disc (C/D) area ratio, C/D horizontal diameter ratio, C/D vertical diameter ratio, disc cup volume and disc rim volume. Results The average thickness and the thickness of temporal and nasal quadrants of CP-RNFL in RP group were significantly thicker than the control group (t=2.27, 3.73, 6.44; P=0.027, 0.00, 0.00), while the thickness of inferior and superior areas were the same as control group(t=-1.49, -1.19; P=0.14, 0.24). The disc area, disc cup area, C/D area ratio, C/D horizontal diameter ratio, C/D vertical diameter ratio, disc cup volume in RP group were significantly bigger than control group (P<0.05), while rim area and rim volume were not significant differences (t=1.75, 0.40; P=0.08, 0.59). Conclusion In comparison with the healthy subjects, the average thickness and temporal and nasal areas of CP-RNFL in RP eyes were thicker, and the disc area, disc cup area, C/D area ratio, C/D horizontal diameter ratio, C/D vertical diameter ratio, disc cup volume in RP eyes were bigger. Key words: Retinitis pigmentosa; Optic disk; Nerve fibers; Tomography, optical coherence