Three Dimensional Retinal Imaging of the Macular Ganglion–Cell Layer With a HR–OCT in Patients With Glaucoma and Correlation With Visual Field Sensitivity

Abstract

Purpose: : High–resolution–OCT (HR–OCT) enables enhanced visualization of the retinal layers, including the ganglion–cell layer in most cases. Together with the rapid scan capability of a frequency–domain OCT a complete macular measurement of the ganglion–cell layer becomes a target for glaucoma diagnosis. The aim was to analyse the thickness of macular retinal ganglion cell layer and to compare it to the sensitivity of visual field (VF).

Methods: : Three dimensional retinal imaging is performed using a second generation frequency domain HR–OCT system with a high axial resolution of 6 microns and up to 20kA–scans/second resulting in 256x256x1024 or 128x512x1024 voxels per volume. 20 eyes of 20 patients with glaucomatous optic neuropathy and paracentral scotomas of different degree were evaluated using 3D HR–OCT retinal imaging. Raster scanning of a 20 by 20 degree field and a depth of 2 mm was performed to cover all locations and provide a complete information about the macular ganglion cell layer. The thickness of (1) the retinal ganglion cell layer (RGCL) and (2) the inner plexiform layer together with the RGCL (compound layer) of the tomograms were correlated with the differential light sensitivity of a 10–2 HFA VF.

Results: : In a preliminary analysis of 8 eyes we compared the VF sensitivity at 3 deg nasal/temoporal/superior/inferior with the corresponding locations of the OCT images. All together we were able to clearly identify all relevant layers of the retina in 28/32 test locations. The corresponding VF sensitivity at the remaining 4 OCT–locations was 17.5 dB (0–26 dB). 6/32 VF test locations showed zero sensitivity. The mean RGCL and compound layer thicknesses of the corresponding OCT locations were 14.2 (±;4.5) and 34.5 (±;6.8) pixels. At 6/32 VF locations the sensitivity was between 1 and 29 dB. The corresponding RGCL and compound layer thicknesses were 18.8 (±;5.3) and 39.1 (±;11.7) pixels. For those VF test locations showing normal sensitivity (>30 dB) the RGCL and compound layer thicknesses were 24.8 (±;5.5) and 49.5 (±;6.9) pixels. Exemplaric data showing the topographic correlation of the thicknesses of the RGCL and the compound layer with the VF will be presented.

Conclusions: : We were able to demonstrate the capability of rapid frequency–domain HR–OCT to measure the retinal ganglion cell layer of the whole macula with one single measurement allowing a topographic correlation to the visual field of glaucoma patients.

Keywords: ganglion cells • imaging/image analysis: clinical • macula/fovea