Abstract
Purpose: :
Fast scanning high resolution optical coherence tomography (HR-OCT) enables quantitative analysis of histological retinal layers. Aim of the study was to test the diagnostic value of overall macular thickness of retinal ganglion cell plus inner plexiform layers (RGIPL) and of the macular retinal nerve fiber layer (RNFL), in comparison with scanning laser polarimetry (SLP).
Methods: :
Macular HR-OCT scans (Cirrus, Carl Zeiss Meditec) were obtained in 24 glaucoma patients (mean deviation -7.1 +/6.6 dB) and 44 age-matched healthy subjects using raster scanning of a 20x20 field at a resolution of 512x128x1024 voxels. The scans were analysed using a software algorithm for automated segmentation and quantification of retinal layers. In this study the overall thicknesses of the RGIPL and the RNFL as well as the retinal thickness (RT) within the central 8deg radius were analysed. Additionally all participants were scanned with SLP (GDx VCC, Carl Zeiss Meditec). The diagnostic value of RNFL, RGIPL, RT and the NFI of GDx VCC were tested using ROC. Additionally t-tests were performed for group comparison.
Results: :
Mean macular 8deg radius RNFL, RGIPL and RT were significantly thinner in glaucoma than in healthy subjects (16.0 +/-5.5 µm vs. 27.8 +/-4.8 µm; 57.4 +/-8.6 µm vs. 72.6 +/-6.9µm; 253.0 +/- 15.4 vs. 281.6 +/-15.8 µm; all comparisons p<0.001). The NFI was higher in glaucoma compared to healthy volunteers (49.4 +/-23.6 vs. 15.1 +/-5.4; p<0.001). ROC values were 0.962 (RNFL), 0.934 (NFI), 0.902 (RGIPL), 0.893 (RT).
Conclusions: :
We demonstrate good diagnostic separation for the 8deg radius mean macular RNFL and RGIPL analyses between glaucoma patients with moderate glaucomatous damage and healthy volunteers. However RT and also the NFI displayed a similar diagnostic value. Analysis of mean macular 8deg radius thickness of the inner retinal layers might not be superior comparing to standard tests like the GDx or the analysis of the mean macular 8deg radius retinal thickness.
Keywords: imaging/image analysis: clinical • nerve fiber layer • macula/fovea