Abstract
Abstract: :
Purpose: To evaluate and compare three dimensional morphometric parameters of optic nerve head obtained by optical coherence tomography (OCT) and Heidelberg Retina Tomograph (HRT). Methods: In the study 86 eyes were included (31 normal eyes (#1), 36 eyes with moderate (#2) and 18 eyes with advanced POAG (#3)). Measurements were performed by Stratus OCT (Zeiss, Model 3000, Software Version 2.0) and HRT (Heidelberg Engineering, Software Version 2.02). OCT–Images were scanned in the "optical disc" mode and analyzed with the "optic nerve head" analysis protocol with two different cup offsets: 0 and 150µm. Composite images of 6 equally spaced linear scans through a common central axis placed in the center of the optic disc were used. Rim volume (RV), disc area (DA), cup area (CA), rim area (RA), cup/disc area ratio (CD) were calculated by OCT and HRT (using standard reference plane). For statistics Pearsons linear regression and Bland–Altmann–Analysis were used. Results:Regression analysis of all eyes showed a very high correlation for CA, CD (R>0.9; p< 0.001), a high correlation for DA, RA (R>0.7; p<0.001) and a good correlation for RV (R=0.55; p<0.001) with both cup offsets. In glaucoma patients (#2 and #3) correlation coefficients were higher than in controls. Bland–Altmann analysis of all eyes revealed that OCT–measurements (cup offset 150µm) are lower for DA (–0.02±0.29 mm²), RA (–0.34±0.38mm²) and RV (–0.08±0.2mm³) and higher for CA (0.34±0.32mm²) and CD (0.16±0.12). With regard to a cup offset=0µm the results changed into the opposite: CA (–0.05±0.22mm²), CD (–0.01±0.08), RA (0.03±0.3mm²) and RV (0.16±0.33mm³). Conclusions: The results of the study show a very good correlation between OCT and HRT in glaucoma patients and a good correlation in normal subjects. However, there was no correlation for RA and RV in controls. Correlation seems to be not influenced by cup offset. Bland–Altmann analysis suggests that a cup offset between 0 and 150µm might provide the best concordance between HRT and OCT measurements.
Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • clinical research methodology