Purpose:
To test the hypothesis that, in early glaucoma, retinal ganglion cell layer (GCL) damage is accompanied by optic nerve head (ONH) neural rim loss using spectral domain optical coherence tomography (SD-OCT).
Methods:
Macular and peripapillary OCT scans (200 × 200 × 1024 voxels, 6 × 6 × 2 mm3) were obtained from left eyes of 58 glaucoma patients and suspects (62.9 ± 14.8 years, 34.5% male) using a CirrusTM HD-OCT machine (Carl Zeiss Meditec, Inc., Dublin, CA). OS images were flipped in a standard fashion. The ganglion cell layer was automatically detected in macular scans by a graph-theoretic approach. Optic disc was segmented from peripapillary scans using a voxel-column classification method. The mean macular GCL thickness in 68 square regions and the neuroretinal rim area in 12 wedge-like regions were measured in the macular and peripapillary scans which were mutually registered in the en-face plane. Each regional GCL thickness was correlated with 12 regional rim areas so that the regional rim area with the highest squared Pearson’s correlation coefficient (r2) was identified.
Results:
The regional GCL thickness across all macular regions had mean (± SD) highest r2 correlation coefficient of 0.178 ± 0.105 with the regional rim area of the ONH. Figures 1C, D show the correspondence of the regional GCL thickness and the regional rim area with the maximum correlation and their highest r2 correlation coefficient, respectively.
Conclusions:
In pre- and early glaucoma, retinal ganglion cell body damage is accompanied by corresponding optic nerve head axonal loss, and this structural damage can be detected using automated image analysis of SD-OCT.
Figure 1. (A) En-face registration of macular and peripapillary OCT projection images. (B) Macular grid including 68 regions (regions 1 - 68) and neuroretinal rim grid including 12 regions (regions a - l). (C) Color-coded correspondence map between regional mean macular GCL thickness and regional rim area. (D) Color-coded highest r2 correlation coefficient map between regional mean macular GCL thickness and regional rim area.
Keywords: image processing • imaging/image analysis: clinical • imaging/image analysis: non-clinical