Sir,

Choroidal osteoma is a rare benign osseous tumor of the choroid, typically affecting healthy eyes of young female subjects.1 It is a clinical diagnosis, classically confirmed by the presence of high reflectivity and acoustic shadowing on B-scan ultrasonography (B-scan) and/or hyperdense plaques at the level of the choroid on computerized tomography scan.1 Here we report a case of a predominantly decalcified choroidal osteoma and the use of enhanced depth imaging optical coherence tomography (EDI-OCT) to confirm the diagnosis.

Case report

A 16-year-old girl presented with a 1 year history of flashing lights in her right eye associated with a yellow-white lesion in the superior juxtapapillary region (Figure 1). B-scan of the lesion showed nonspecific, mild choroidal thickening with no hyper-reflective areas or posterior shadowing (Figure 2). EDI-OCT revealed a small area of subretinal fluid superior to the optic nerve and a discrete choroidal mass measuring 387 μm in thickness, with variable intrinsic reflectivity adjacent to areas of choroidal atrophy (Figures 3a and b). These findings are consistent with a predominantly decalcified choroidal osteoma.

Figure 1
figure 1

Right fundus photograph showing large superior juxtapapillary choroidal lesion.

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Figure 2
figure 2

B-scan showing mild thickening but no hyperreflectivity or posterior acoustic shadow.

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Figure 3
figure 3

(a) EDI-OCT section illustrating choroidal mass with variable intrinsic reflectivity. Note the intrinsic hyper-reflective dots (red arrow) and isoreflective areas and well-defined scalloped posterior border. Adjacent to this mass is atrophic choroid (white arrow). (b) EDI-OCT section below Figure 3a illustrating thickened outer retina (black arrow) and underlying subretinal fluid. Note that there is increased transmission of light through the atrophic choroid.

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Comment

Classically described by Gass et al in 1978,1 choroidal osteoma is typically a unilateral, well-demarcated yellow-white to orange juxtapapillary or macula lesion located within the choroid. Using spectral domain OCT, Navajas et al described a distinctive lattice work pattern of reflectivity in some choroidal osteomas,2 similar to the intratumoral channels described histopathologically by Gass.1 However, choroidal osteoma change over time and can undergo decalcification,3 losing their typical appearance on B-scan. Decalcification is often associated with shrinkage of the tumor, resulting in RPE and choriocapillaris atrophy.3 In our case, the residual tumor measured only 387 μm in thickness on EDI-OCT, making it undetectable by B-scan. The characteristic features of the residual tumor, demonstrated on EDI-OCT, confirmed the clinical suspicion of choroidal osteoma, albeit predominantly decalcified.

EDI-OCT has recently emerged as a noninvasive technique to visualize the choroid in greater detail,4 capable of measuring choroidal tumors up to 1 mm in thickness.5 This technique can serve as an adjunctive modality to distinguish predominantly decalcified choroidal osteomas from other choroidal lesions and enable assessment of the overlying retina and future monitoring.