Comparison of Spectral-Domain Optical Coherence Tomography and Fundus Autofluorescence in Patients With Geographic Atrophy

Abstract

Purpose: : The purpose of this study is to evaluate the capability of spectral-domain OCT (SD-OCT) to provide solid and reproducible parameters for the grading of geographic atrophy (GA) concerning lesion size in comparison to the current gold standard, the fundus autofluorescence (FAF).

Methods: : 81 eyes of 42 patients with severe vision loss due to GA secondary to AMD were enrolled in this prospective study. Patients underwent FAF and SD-OCT imaging(Spectralis^TM HRA-OCT). The images were then separately graded by two independent readers from the Vienna Reading Center (VRC). The FAF images were graded concerning size of atrophy. The SD-OCT B-scans were imported into a proprietary software that allows to mark areas in the B-scans and projects them to an en face image with automated planimetric evaluation.The gradings in the B-scans were: complete and incomplete choroidal signal enhancement, complete and incomplete loss of the retinal pigment epithelium (RPE), subsidence of the outer plexiform layer (OPL), loss of the OPL and loss of the external limiting membrane. These areas were then compared to the area measured in the FAF in order to determine the best fitting parameter in grading SD-OCT B-scans concerning lesion size.

Results: : The mean GA lesion size in the FAF was 8.97± 7.55 mm². measured by grader 1 (G1) and 9.54 ± 8.15 mm² measured by Grader 2 (G2). The best matching and correlating areas in SD-OCT compared to the areas measured in FAF were the area of complete choroidal signal enhancement with an accordance of 98%, area of subsidence of the OPL (84%) and area ELM loss (92%). The FAF area correlated with the area of complete RPE loss in only 40%.

Conclusions: : It can be assumed that the neurosensory layer alteration can be monitored prior to the total loss of RPE in GA and that a differentiation between lost RPE and altered RPE seems to be difficult while grading the grayscale FAF images.SD-OCT appears to be an appropriate imaging modality in monitoring patients with GA, as the area of atrophy can be accurately measured and information concerning all retinal layers can be gained.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • age-related macular degeneration • retina