Optical coherence tomography angiography in choroidal melanoma and nevus

Fariba Ghassemi,1,2 Reza Mirshahi,1,2 Kaveh Fadakar,1,2 Siamak Sabour3 1Retina & Vitreous Service, 2Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, 3Safety Promotion and Injury Prevention Research Centre, Department of Clinical Epidemiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran Synopsis: In optical coherence tomography angiography, the choroidal vascular flow rate in choroidal melanoma is significantly lower than that in choroidal nevus.Objective: The objective of this study was to describe the choriocapillaris and retinal features imaged by optical coherence tomography angiography (OCTA) in eyes with choroidal nevus from small malignant choroidal melanoma.Methods: In this retrospective, noninvasive, observational study, 11 patients diagnosed with small choroidal mass (five with choroidal nevus and six with malignant melanoma) who underwent dilated fundus examination, ocular ultrasonography and OCTA images were compared.Results: In choroidal nevus of all patients, OCTA demonstrated a hyporeflective mass with no significant deformity of choroidal vasculature and an intact retinal pigment epithelium (RPE)–Bruch’s membrane complex. The flow void mass was surrounded by an intense vascular rim named as surface microvasculature (SMV) that had an approximately similar flow rate median of 63.68 mm2 (60.42–67.62 mm2), comparable with the median of the contralateral normal eye of 61.77 mm2 (60.42–64.53 mm2; P>0.09) for nevi. OCTA showed an obscured Bruch’s membrane–RPE–Bruch’s membrane complex and outer retinal layer in choroidal melanomas. Choriocapillaris flow rate over the melanomas was 55.73% (41.93%–60.82%), and the corresponding normal areas had a flow area of 62.75% (61.99%–63.10%; P=0.01). A flow rate difference between choroidal melanoma and nevus was significant (P=0.006). Axial and peripheral feeding vessels were more dilated and tortuous compared with benign nevi.Conclusion: Decreased flow rate of SMV of choroidal melanoma cases compared with nevi was a significant finding. Detection of characteristic vascular features of choroidal melanoma by OCTA could make OCTA an assuring diagnostic modality to differentiate malignant lesions. Keywords: melanoma, choroidal nevus, OCT, OCTA, uveal melanom