Imaging of the Retinal Nerve Fibre Layer with Spectral-domain Optical Coherence Tomography in Patients with Glaucoma

Evaluation of the retinal nerve fibre layer (RNFL) is key to diagnosing and monitoring changes in glaucoma. Optical coherence tomography (OCT) is a non-invasive, objective, quantitative method that provides realtime in vivo images of the retina. The new spectral-domain OCTs have increased resolution and acquisition speed compared with earlier time-domain OCTs, enabling the generation of highly detailed 3D images. Axial resolution has also been improved from 10 to 3–5μm. Thus, spectral-domain OCT is a promising new clinical tool for evaluating the RNFL in glaucoma and other retinal diseases. Recent studies report that spectral-domain OCT provides peri-papillary RNFL measurements with excellent repeatability and reproducibility. The reduced variability compared with time-domain OCT may improve detection of disease progression in glaucoma patients. In cross-sectional studies, most authors suggest that the two OCT systems have similar diagnostic potential to discriminate between healthy and glaucoma patients. Nevertheless, the Cirrus HD-OCT (spectral-domain) tends to yield a slightly higher sensitivity at fixed specificities than the Stratus OCT (time-domain) for glaucoma diagnosis. In healthy subjects and patients with glaucoma, RNFL thickness measurements acquired with the two OCT systems correlated well, but their values cannot be used interchangeably.