Small Symptomatic Unilateral Choroidal Osteoma Diagnosed with Enhanced-Depth Imaging Optical Coherence Tomography and Thin-Slice Computed Tomography: 2 Clinical Cases

Background: Choroidal osteoma is a rare, benign, ossifying intraocular tumor of unknown etiology. While patients with choroidal osteoma usually show distinct large yellowish subretinal lesions, some could have small lesions, making the differential diagnosis difficult. We experienced 2 cases of small symptomatic unilateral osteoma approximately 1.0-mm disc diameter in size. Methods: Retrospective medical charts of 2 patients with small symptomatic unilateral osteoma were reviewed. Fundus examination, spectral domain enhanced-depth optical coherence tomography (EDI-OCT), fluorescein angiography, indocyanine green angiography, B-scan ultrasonography (USG), and X-ray computed tomography (CT) were performed. Results: Case 1: a case of a 41-year-old male. Fundus examination revealed a yellowish-white lesion of 1.0-mm disc diameter in size. EDI-OCT of the lesion shows sub-RPE elevation. B-scan USG was not definite for diagnosis. Thin-slice (2 mm) CT scan revealed a choroidal osteoma. Case 2: a case of a 70-year-old male. Fundus examination revealed a yellowish-white lesion of 0.9-mm disc diameter. EDI-OCT showed sub-RPE elevation without serous retinal detachment and horizontal lamellar-like structure within the lesion. B-scan USG suggested acoustic shadowing, but it was unclear. The thin-slice CT scan confirmed bony tissue at the lesion. Conclusions: We report 2 cases of small choroidal osteoma. Diagnosis of small yellowish subretinal lesions is sometimes difficult. Characteristic findings with EDI-OCT may sometimes suggest this disease, and thin-slice CT could help to diagnose choroidal osteoma.