Purpose: To report the use of optical coherence tomography (OCT) in verifying the specificity of the ultrasonographic "apical double echo" sign in detecting subtle subretinal fluid (SRF) associated with small choroidal melanocytic tumors.
Methods: Retrospective review of consecutive patients demonstrating ultrasonographic "apical double echo," indicative of subtle SRF, who concurrently underwent OCT on initial evaluation of untreated small choroidal melanocytic tumors. Ultrasonography was performed with eyecubed version 3, ophthalmic ultrasound system (Ellex/Innovative Imaging, Inc, Adelaide, Australia) and OCT with spectral-domain OCT, Cirrus HD-OCT, model 4000 (Carl Zeiss; Meditec, Dublin, CA). Optical coherence tomographic images were examined to verify the presence of SRF and to identify other retinal pathology producing apical double echo in the absence of SRF.
Results: The study included 36 patients. With OCT, subtle SRF was present at tumor apex and/or margins in 20 patients (55%) and absent in 16 patients (45%). When SRF was present, it was detected at tumor apex only in 3 of 20 patients (14%), gravitated at the inferior margin only in 13 of 20 patients (64%), and at apex and inferior margin in 4 of 20 patients (22%). When SRF was absent, the retina over the tumor showed degenerative cystic changes in 10 of 16 patients (65%), retinal thickening in 4 of 16 patients (25%), and retinal pigment epithelium detachment in 2 of 16 patients (10%), accounting for the ultrasonographic apical double echo.
Conclusion: Ultrasonography showed limited specificity for detecting subtle SRF related to small choroidal melanocytic tumors, with 45% of patients showing ultrasonographic apical double echo in the absence of SRF with OCT. The retinal changes that yielded false-positive results included retinal cystic degenerations, retinal thickening, and retinal pigment epithelium detachment. Optical coherence tomography is preferred to verify the presence of subtle SRF over small choroidal melanocytic tumors, provided that the inferior tumor margin is included in imaging.