Performance of OCT segmentation procedures to assess morphology and extension in geographic atrophy

. Purpose:  Investigating segmentation procedures and morphological findings in time domain (TD) and current spectral domain (SD) optical coherence tomography (OCT) devices in patients with geographic atrophy (GA). Methods:  Fifty eyes of 46 patients with GA secondary to AMD and 15 control eyes were examined in this prospective noninterventional comparative case series. All patients underwent Stratus (model 3000), Cirrus (Carl Zeiss Meditec), Spectralis (Spectralis HRA+OCT; Heidelberg Engineering) and 3D-OCT-1000 (Topcon). Automated segmentation analyses were compared. An overlay of scanning laser ophthalmoscope (SLO) and three-dimensional retinal thickness (RT) maps were used to investigate whether areas of retinal thinning correspond to areas of retinal pigment epithelium (RPE) atrophy. Results:  Geographic atrophy areas identified in SLO scans were significantly larger than areas of retinal thinning in RT maps. No convincing topographic correlation could be found between areas of retinal thinning and actual GA size as identified in SLO and fundus photography. Spectralis OCT showed significantly more mild and severe segmentation errors than 3D and Cirrus OCT. Conclusion:  This study showed substantial limitations in identifying zones of GA reliably when using automatic segmentation procedures in current SD-OCT devices. This limitation should be addressed to visualize and document RPE loss realistically in a frequent disease like GA.