Optic nerve head melanocytoma: Optical coherence tomography/angiography features.

Purpose: The objective of this study was to identify the diagnostic features of optic nerve head melanocytoma (ONH-MCT) on spectral domain optical coherence tomography (SD OCT) and OCT angiography (OCT-A). Methods: Retrospective study of 11 patients for their demographic, clinical features and imaging including SD OCT (tumour location, extent and interface) and OCT-A (surface and intrinsic vascularity) were reviewed. Flow rate percentage (FR %) was calculated over the lesion and compared to fellow eye and similar pigmented lesions. Results: The average age was 52.8 ± 10.9 years. ONH-MCT tumors occupied 3-tissue spaces- optic disc (n = 2), retinal layer (n = 5) and retina-choroidal layers (n = 4). SD OCT (11 eyes) showed elevated hyper reflective disorganized retinal layers with posterior shadowing (9 eyes) and hyper reflective dots within the tumor (all eyes). Microvascular features on OCT-A (8 eyes) in radial peripapillary capillary slab showed surface vascularization (7 eyes) and intrinsic vascularity in choroidal slab (8 eyes) with surrounding hypo reflective boundary. The mean FR % was higher at 65.1 ± 3.77% (CI: 61.9-68.2) compared to mean FR at 60.4 ± 1.06% (CI: 59.5-61.2) in the fellow eye (p = 0.01). Comparison with nevus and melanoma SD OCT showed a high reflective choroidal layer with normal or irregular outer retinal layers respectively; OCT-A showed hypo reflective area at the center with hyper reflective boundary and iso reflective area at center with hyper reflective boundary respectively. Conclusion: SD OCT and OCT-A features may help to differentiate ONH-MCT from clinically similar looking pigmented lesions like nevus and melanoma.