Posterior Scleral Bowing With Choroidal Nevus on Enhanced-Depth Imaging Optical Coherence Tomography

Abstract

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.

Detecting Progression of Melanocytic Choroidal Tumors by Sequential Imaging: Is Ultrasonography Necessary?

“…With small, posterior tumors, enhanced depth imaging OCT (EDI-OCT) may be a reasonable alternative in community practices. Enhanced depth imaging OCT can detect posterior scleral bowing in 5–14% of choroidal nevi [ 37 , 38 ], especially those with less/mixed pigmentation, posterior location, or a surrounding halo [ 37 ]. In such cases, ultrasonographic measurement may underestimate true tumor thickness although, in most instances, ultrasound overestimates the thickness of minimally elevated choroidal tumors.…”

Photoreceptor Arrangement Changes Secondary to Choroidal Nevus

“…Cone mosaic changes on AO imaging could result from an insidious insult attributed to melanocyte accumulation that potentially disturbs the choriocapillaris flow and consequently disrupts photoreceptor outer segments. Late secondary outer retinal changes, such as retinal pigment epithelial and intraretinal cystic changes, photoreceptor loss, and retinal pigment epithelial detachment, can then be detected by EDI SD-OCT. 15 In fact, researchers 16 showed that similar melanocytedriven mechanical effect could cause scleral bowing. Because AO detected photoreceptor changes, we used microperimetry to check for retinal function.…”

Importance of Optical Coherence Tomography and Optical Coherence Tomography Angiography in the Imaging and Differentiation of Choroidal Melanoma: A Review

“…In the case of nevi presenting with at least three of the features mentioned above, the risk of malignant transformation during the next 5 years is estimated at 50% [ 50 ]. Annual rate of malignant transformation of choroidal nevi in the white population accounts for 1/8.845 [ 51 ].…”