Enhanced depth imaging optical coherence tomography of small choroidal melanoma: Comparison with choroidal nevus

Objective: To evaluate characteristics of small choroidal melanoma using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT). Design: Retrospective comparative analysis. Results: Of 37 eyes with small choroidal melanoma imaged using EDI-OCT, the mean tumor thickness was 1025 μm by EDI-OCT compared with 2300 μm by ultrasonography. By EDI-OCT, choroidal features included optical shadowing in 36 (100%) and overlying choriocapillaris thinning in 37 (100%). Outer retinal features included shaggy photoreceptors in 18 (49%), as well as absence (structural loss) of photoreceptors in 9 (24%), inner segment-outer segment junction in 24 (65%), external limiting membrane in 16 (43%), outer nuclear layer in 6 (16%), and outer plexiform layer in 4 (11%). Inner retinal features included irregularity of inner nuclear layer in 3 (8%), inner plexiform layer in 3 (8%), ganglion cell layer in 3 (8%), and nerve fiber layer in 2 (5%). Also identified were subretinal fluid in 34 (92%), subretinal lipofuscin deposition in 35 (95%), and intraretinal edema in 6 (16%). Using EDI-OCT, a comparison with similarsized choroidal nevus revealed that small choroidal melanoma showed increased tumor thickness, subretinal fluid, subretinal lipofuscin deposition, and retinal pigment epithelium atrophy. Statistically significant EDI-OCT features for small choroidal melanoma included intraretinal edema (P=.003), shaggy photoreceptors or loss of photoreceptors (P=.005), loss of external limiting membrane (P=.008), loss of inner segment-outer segment junction (P=.02), irregularity of inner plexiform layer (P=.04), and irregularity of ganglion cell layer (P=.04) (t test and χ ² test). Shaggy photoreceptors were found overlying small choroidal melanoma in 18 (49%) but were not observed overlying choroidal nevus (P<.001). Conclusions: Small choroidal melanoma tumor thickness was overestimated by 55% on ultrasonography compared with EDI-OCT. The EDI-OCT features of small choroidal melanoma compared with choroidal nevus include increased tumor thickness, subretinal fluid, subretinal lipofuscin deposition, and retinal irregularities, including shaggy photoreceptors.