Importance: Recognition of posterior scleral bowing with choroidal nevus is essential to avoid an underestimation of tumor thickness.
Objective: To describe a particular observation of posterior scleral bowing associated with choroidal nevus on enhanced-depth imaging (EDI) optical coherence tomography (OCT).
Design, setting, and participants: 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.
Interventions: Retrospective medical record review and multimodal imaging including fundus photography, autofluorescence, infrared reflectance, ultrasonography, and EDI-OCT.
Main outcomes and measures: Clinical and imaging characteristics.
Results: 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).
Conclusions and relevance: 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.