Posterior scleral bowing with choroidal nevus on enhanced-depth imaging optical coherence tomography.

Abstract

Recognition of posterior scleral bowing with choroidal nevus is essential to avoid an underestimation of tumor thickness. To describe a particular observation of posterior scleral bowing associated with choroidal nevus on enhanced-depth imaging (EDI) optical coherence tomography (OCT). Retrospective observational case series at a referral center involving 17 eyes of 17 patients. Patients were seen from June 2013 to July 2014, with all data collected and analyzed from June 2014 to July 2014. Retrospective medical record review and multimodal imaging including fundus photography, autofluorescence, infrared reflectance, ultrasonography, and EDI-OCT. Clinical and imaging characteristics. Analysis of 318 consecutive patients with choroidal nevus imaged over a 1-year period revealed that 17 cases (5%) demonstrated the EDI-OCT feature of posterior scleral bowing. Of these 17 cases, the mean patient age was 58 years (median, 58 years; range, 36-75 years) and there were 6 men (35%) and 11 women (65%). The nevus was classified as pigmented (n = 3; 18%), nonpigmented (n = 2; 12%), and mixed pigmentation (n = 12; 71%), and with no surrounding halo (n = 7; 41%). Associated features included overlying drusen (n = 9; 53%), retinal pigment epithelial alterations (n = 9; 53%), subretinal fluid (n = 5; 29%), and orange pigment (n = 3; 18%). The nevus was clinically estimated to be of 4.91-mm basal dimension and measured ultrasonographically at 1.59-mm thickness. By EDI-OCT, the nevus mean thickness was 628 µm (0.63 mm). All cases demonstrated posterior scleral bowing with mean scleral excavation of 398 µm (median, 377 µm; range, 134-739 µm). Underlying the nevus, the scleral thickness was not measurable; however, at the nevus margin, the choroid and sclera appeared normal. Clinical features correlated with posterior scleral bowing included reduced distance to the optic disc (difference, 1.3 mm; 95% CI, -2.95 mm to 5.51 mm; P = .01) and the foveola (difference, 2.14 mm; 95% CI, 0.80 mm to 3.48 mm; P < .001), as well as the presence of surrounding halo (difference, 36%; 95% CI, 16.86% to 59.27%; P < .001). Choroidal nevus can show focal posterior scleral bowing on EDI-OCT in 5% of cases. This finding was related to more posterior location of nevus, less/mixed pigmentation, and surrounding halo. This finding could lead to underestimation of tumor thickness as the tumor bows backward rather than forward.