Purpose
Swept Source optical coherence tomography (SS-OCT) is a new imaging technology, which has shown promise to visualize the lamina cribrosa (LC), a principal site of glaucomatous optic nerve damage. In this study, we compared SS-OCT to Spectral Domain optical coherence tomography (OCT) with Enhanced Depth Imaging (EDI-OCT) in order to assess inter-observer variability of LC defects in glaucoma patients. Furthermore, we assessed ophthalmic features associated with LC defects detected by both devices.
Methods
38 eyes of 19 patients with open angle glaucoma underwent radial and horizontal optic nerve serial scans using the EDI-OCT (Heidelberg) and the SS-OCT (Topcon) in a single visit. Two glaucoma specialists performed interpretation of the images and classified eyes into four categories: no defect, pre-laminar defects, focal laminar defects and laminar disinsertions. Disc photographs were used to rule out artifact from vascular shadowing. Characteristics related to glaucoma, such as history of disc hemorrhage, intraocular pressure, Humphrey Visual Field mean deviation, were compared among eyes in those categories. Spearman’s rank test was performed for correlated measurements and Kappa agreement was used to assess the inter-observer variability.The one-way analysis of variance test was used to determine clinical factors associated with LC defects.
Results
32 (84%) serial scans from SS-OCT and 29 (76%) serial scans from EDI-OCT were included in the analysis. The interpretation of the LC images was significantly correlated between the two observers using SS-OCT (r=0.756,p<0.0001) and EDI-OCT (r=0.655,p<0.001), with comparable inter-observer agreements (k=0.537 vs. k=0.521, respectively). In 8 (23%) eyes with laminar abnormalities, detected by both observers, the incidence of pre-laminar defect (fig 1A), focal laminar defect (fig 1B) and laminar disinsertion (fig 1C) was 37,5%, 37,5% and 25%, respectively. None of the clinical factors analyzed had correlation with LC abnormalities (ANOVA: p>0.1).
Conclusions
Preliminary results suggest that SS-OCT and EDI-OCT images are consistent and both OCTs exhibit good inter-observer agreement when imaging the LC in glaucoma patients. The clinical significance of these defects in glaucoma detection and management remains to be elucidated.
Keywords: 550 imaging/image analysis: clinical •
577 lamina cribrosa •
629 optic nerve