A 24-year-old woman presents with gradual blurring of central vision in the left eye for 3 months. Funduscopic examination reveals a yellow-white, flat lesion adjacent to the optic disc measuring 6 mm with sharply scalloped margins. The structure marked **A** in the diagram represents the ossified plaque characteristic of choroidal osteoma. Which of the following imaging findings would be MOST SPECIFIC for confirming the diagnosis of this lesion?
A. Fluorescein angiography demonstrating early patchy hyperfluorescence with late staining
B. Computed tomography scan showing radiopacity consistent with calcium density
C. B-scan ultrasonography showing a highly reflective plaque with posterior acoustic shadowing
D. Optical coherence tomography revealing lamellar bone with horizontal high-reflectivity lines
Explanation
Why B-scan ultrasonography showing a highly reflective plaque with posterior acoustic shadowing is right
The yellow-white ossified plaque (marked A) in choroidal osteoma is composed of mature lamellar bone with Haversian canals. This bone structure is pathognomonic on B-scan ultrasonography, which demonstrates a highly reflective plaque with characteristic posterior acoustic shadowing (orbital shadow) — a finding that is virtually diagnostic of choroidal osteoma and distinguishes it from other choroidal lesions. This imaging modality is the gold standard for identifying the ossified nature of the plaque and confirming the diagnosis (Shields CL et al. Surv Ophthalmol 1988; AAO BCSC Section 4).
Why each distractor is wrong
Fluorescein angiography demonstrating early patchy hyperfluorescence with late staining: While FA may show these findings in choroidal osteoma, this pattern is not specific — it can occur with other choroidal lesions and does not directly demonstrate the ossified nature of the plaque marked A.
Optical coherence tomography revealing lamellar bone with horizontal high-reflectivity lines: Although OCT can show lamellar bone architecture, this finding is not as specific or pathognomonic as the acoustic shadowing on B-scan. OCT is better for assessing overlying RPE/photoreceptor atrophy and complications like CNV.
Computed tomography scan showing radiopacity consistent with calcium density: CT demonstrates the calcification/ossification but is not the first-line or most specific imaging modality. B-scan ultrasonography with posterior acoustic shadowing is more characteristic and readily available in clinical practice.
High-YieldNEET PG
Posterior acoustic shadowing on B-scan ultrasonography is the pathognomonic imaging finding that confirms choroidal osteoma and distinguishes it from amelanotic melanoma, hemangioma, and other choroidal lesions.
