Facilitating glaucoma diagnosis with intereye neuroretinal rim asymmetry analysis using spectral-domain optical coherence tomography

Purpose—To determine whether intereye asymmetry of a three-dimensional neuroretinal rim parameter, the minimum distance band, is useful in differentiating normal eyes from those with open-angle glaucoma. Materials and Methods—This is a cross-sectional study of 28 normal subjects and 33 glaucoma sub-jects. Subjects underwent spectral domain optical coherence tomography imaging of both eyes. From high-density raster scans of the optic nerve head, a custom-designed segmentation algorithm calculated mean minimum distance band neuroretinal rim thickness globally, for four quadrants, and for four sectors. Inter-eye minimum distance band thickness asymmetry was calculated as the absolute difference in minimum distance band thickness values between the right and left eyes. Results—Increasing global minimum distance band thickness asymmetry was not associated with increasing age or increasing refractive error asymmetry. Glaucoma patients had thinner mean neuroretinal rim thickness values compared to normal patients (209.0 μm vs 306.0 μm [P < 0.001]). Glaucoma subjects had greater intereye thickness asymmetry compared to normal subjects for the global region (51.9 μm vs 17.6 μm [P < 0.001]) as well as for all quadrants and all sectors. For detecting glaucoma, a thickness asymmetry value >28.3 μm in the inferior quadrant yielded the greatest sum of sensitivity (87.9%) and specificity (75.0%). Globally, thickness asymmetry >30.7 μm yielded the greatest sum of sensitivity (66.7%) and specificity (89.3%). Conclusions—This study indicates that intereye neuroretinal rim minimum distance band asymmetry measurements, using high-density spectral domain optical coherence tomography volume scans, may be an objective and quantitative tool for assessing patients suspected of open-angle glaucoma.