Purpose: The purpose of this study was to determine whether optical density ratio (ODR) of subretinal fluid (SRF) on optical coherence tomography (OCT) differs between choroidal naevi and melanomas.
Methods: One hundred ninety-nine patients (one eye per patient) presenting choroidal melanoma or choroidal naevus with SRF on OCT, evaluated between February and June 2019, were retrospectively included. Other retinal conditions, opaque media, and low-quality OCT were excluded. Mean pixel intensity of SRF (range = 0-255) was quantified using a semi-automated procedure by a masked observer on standard horizontal OCT sections. Mean vitreous intensity served as the reference for ODR.
Results: One hundred twenty-eight patients with choroidal melanoma and 71 patients with choroidal naevus were included in this study. ODR (mean ± SD) was higher in melanomas (181 ± 64) than in naevi (78 ± 48, P < 0.0001). ODR was correlated to lesion thickness (P < 0.0001, r = 0.27), largest basal diameter (P = 0.028, r = 0.16) and, among naevi, to the number of risk factors for growth into melanoma (P = 0.032, r = 0.22). Among 110 patients with naevi or melanoma who underwent fluorescein angiography, ODR was 120.7 ± 550.1 in eyes presenting angiographic pinpoints versus 14.19 ± 26.0 in eyes that did not (P = 0.06). Fourteen eyes with naevi that transformed into melanoma over 3 years had a mean baseline ODR of 94.7 ± 243.5 compared to 4.01 ± 9.74 in 28 matched naevi eyes of similar size that did not transform (P = 0.027).
Conclusions: SRF ODR is higher in choroidal melanoma compared to choroidal naevi. This OCT-derived imaging marker is also higher in choroidal naevi with the potential to transform into melanoma, compared to stationary naevi.