The Correlation Between Neuroretinal Rim Area and Peripapillary Retinal Nerve Fiber Layer Thickness on 12-Clock Hour Sectors in Open Angle Glaucoma and Nonarteritic Ischemic Optic Neuropathy

Abstract

Purpose: : To compare the correlation between neuroretinal rim area of the optic nerve head and retinal nerve fiber layer thickness (rim-RNFL correlation) on 12 clock hour segments between subjects with open angle glaucoma (OAG) and with nonarteritic ischemic optic neuropathy (n-AION).

Methods: : One hundred and thirteen subjects with OAG, and 22 with n-AION were included in this cross sectional study. The rim-RNFL correlation of OAG patients on clock hour, quadrant, and global area basis measured with Heidelberg Retina Tomograph (HRTII; Heidelberg Engineering) and optical coherence tomography (CirrusOCT: Carl Zeiss Meditec, Inc.) was examined with linear and nonlinear regression fits including second order polynomial and logarithmic regressions. We tested whether subjects with n-AION were out of 95 % prediction interval (PI) of the rim-RNFL correlation of OAG subjects in each defective areas of CirrusOCT.

Results: : Statistically significant rim-RNFL correlation of OAG subjects in both linear and nonlinear regression was observed in all clock hour segments (0.069 < r² < 0.64, P <0.05, respectively) except 4 and 9 o’clock, and linear regression was not inferior to the nonlinear regressions (P >0.05, respectively). 90.3% (range 75 ~100 %) of defective RNFL clock-hour sectors in n-AION subjects were out of the 95 % PI level of linear regression from OAG subjects, compared with 75.0% (range: 0~100 %) on quadrant basis and 59.1% (range: 0~100 %) on global area basis (P = 0.04, and P = 0.0061, respectively; paired t-test).

Conclusions: : Clock hour based linear regression of the rim-RNFL correlation with 95 % PI limit well differentiated n-AION from OAG, and was superior to quadrant and global area based analysis.

Keywords: optic disc • imaging/image analysis: clinical • neuro-ophthalmology: optic nerve