Reproducibility of SD-OCT-based ganglion cell-layer thickness in glaucoma using two different segmentation algorithms.

PURPOSE: To compare the reproducibility of spectral-domain optical coherence tomography (SD-OCT)-based ganglion cell-layer-plus-inner plexiform-layer (GCL+IPL) thickness measurements for glaucoma patients obtained using both a publicly available and a commercially available algorithm.
METHODS: Macula SD-OCT volumes (200 × 200 × 1024 voxels, 6 × 6 × 2 mm(3)) were obtained prospectively from both eyes of patients with open-angle glaucoma or with suspected glaucoma on two separate visits within 4 months. The combined GCL+IPL thickness was computed for each SD-OCT volume within an elliptical annulus centered at the fovea, based on two algorithms: (1) a previously published graph-theoretical layer segmentation approach developed at the University of Iowa, and (2) a ganglion cell analysis module of version 6 of Cirrus software. The mean overall thickness of the elliptical annulus was computed as was the thickness within six sectors. For statistical analyses, eyes with an SD-OCT volume with low signal strength (<6), image acquisition errors, or errors in performing the commercial GCL+IPL analysis in at least one of the repeated acquisitions were excluded.
RESULTS: Using 104 eyes (from 56 patients) with repeated measurements, we found the intraclass correlation coefficient for the overall elliptical annular GCL+IPL thickness to be 0.98 (95% confidence interval [CI]: 0.97-0.99) with the Iowa algorithm and 0.95 (95% CI: 0.93-0.97) with the Cirrus algorithm; the intervisit SDs were 1.55 μm (Iowa) and 2.45 μm (Cirrus); and the coefficients of variation were 2.2% (Iowa) and 3.5% (Cirrus), P < 0.0001.
CONCLUSIONS: SD-OCT-based GCL+IPL thickness measurements in patients with early glaucoma are highly reproducible.