Introduction: The newly developed Optical Coherence Tomography Angiography (OCT-A) has provided new means to depict the vascular plexus in neovascular age-related maculadegeneration (nAMD). If these images are to be used as a basis for therapeutic decision it is of vital importance to classify choroidal neovascularizations (CNV) as either classic or occult. This study aims at comparing the findings in OCT-A imaging of CNV with the traditional multimodal imaging through Fluorescein Angiography (FLA) and Indocyanin-green angiography (ICGA).
Methods: For this investigation 13 eyes of 13 patients (two female, 11 male, mean age: 79.7 years) with CNV on the basis of untreated nAMD were studied using FLA, ICGA, Spectral-Domain OCT (SD-OCT, Spectralis OCT, Heidelberg Engineering, Heidelberg, Deutschland) and OCT-A (Optovue RTVue XR Avanti, Optovue Inc., Freemont, CA, USA). All CNV were classified on the basis of SD-OCT and OCT-A images by two independet raters. Thereafter FLA and ICG images were analysed to set the gold standard of the classification (5 patients with (mostly) classic CNV, two patients with minimal classic CNV, 6 patients with occult CNV) and the rating were compard to the prior SD-OCT and OCT-A results.
Results: Fundamentally both the segmentation as well as the identification of artifacts is of essential importance when analyzing OCT-A images. Under the given circumstances, 88% of eyes (rater 1: 12 of 13 eyes, rater 2: 11 of 13 eyes) were correctly classified as either classic or occult CNV on the basis of SD-OCT and OCT-A images. Based on the CNV subgroups, 93% of classic CNV were identified using OCT-A images (rater 1: 6 of 7 eyes correct, rater 2: 7 of 7 eyes correct). Occult CNV instead were correctly classified as such in 83% of patients (rater 1: 6 of 6 eyes correct, rater 2: 4 of 6 eyes correct). The interrater agreement was 77% (10 of 13 eyes).
In general it was noted that the more the retina was pathologically altered, e.g. by edema or vascular pigment epithelium detachment, the harder it got to correctly classify the CNV. The longer time needed for image acquisition in OCT-A compared to FLA and ICGA also causes more movement artefacts, which sometimes cannot easily be distinguished from pathologies.
Discussion: These results show that OCT-A can be used as an interesting addition in the diagnosis of CNV in nAMD. All CNV could be visualized using OCT-A and especially classic CNV could be clearly recognised in most cases. Occult CNV by contrast could be identified in slightly fewer cases. By further improving the three-dimensional presentability, the reduction of the time needed for image acquisition and an improved eye-tracking to reduce motion artefacts the diagnostic potential of OCT-A technology will certainly be improved even more.
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