Choroidal osteoma (choroidal osseous choristoma) is an unusual benign bony tumor that has received much attention in the literature (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53). Its etiology and pathogenesis are unknown, but it has typical clinical and histopathologic features. It is unilateral in 79% of cases, is bilateral in 21% of cases, and is most often diagnosed in young adult women (67%) (8). More than one family member has been affected in 5% of cases (8, 9, 10). The mean age at diagnosis is 26 years, the median age is 25 years, and it has been diagnosed in young children (17,36). Most cases are not strictly congenital: We have noted the development of choroidal osteoma in previously normal choroid. Bilateral total blindness from bilateral atypical choroidal osteoma has been recognized (15). In that case, the mother eventually had a daughter who had bilateral choroidal osteoma.

Choroidal osteoma typically appears as a yellow-orange placoid, juxtapapillary or macular lesion with well-defined margins that may show pseudopodia-like projections. One study of 74 eyes with choroidal osteoma disclosed that at 10 years, tumor growth was documented in about 50%, tumor decalcification in about 50%, visual loss greater than three lines in 50%, vision of 20/200 or worse in 50%, and development of choroidal neovascular membrane in 30% (figures rounded to nearest 5%) (8). Lesions presumed to be choroidal osteoma have been associated with other ocular abnormalities, including Rieger anomaly, histiocytosis X, and others, but these associations are possibly coincidental (18,29).

The differential diagnosis includes several conditions, including sclerochoroidal calcification (21), intrascleral cartilage associated with organoid nevus syndrome (52), choroidal metastasis, amelanotic choroidal nevus and melanoma, choroidal granuloma, posterior scleritis, subretinal fibrosis, and other nonpigmented fundus lesions. The first two can be highly echogenic with ultrasonography and be indistinguishable from choroidal osteoma using that technique. However, the ophthalmoscopic features are different (21,52).

Fluorescein angiography shows patchy early hyperfluorescence and intense late staining of the lesion (1, 2, 3, 4, 5). Vascular tufts are sometimes seen emerging through the bone. A-scan and B-scan ultrasonography show a highly reflective echo that persists at lower sensitivity. CT reveals a choroidal plaque with bone density. MRI shows the tumor to be hyperintense to vitreous on the T1-weighted image and hypointense to vitreous on the T2-weighted image, similar to most other choroidal tumors (51). The pathogenesis of choroidal osteoma is unknown. Serum calcium, phosphorus, and alkaline phosphatase levels are generally normal.

Histopathologically, choroidal osteoma is composed of mature bone at the level of the choroid. The overlying retinal pigment epithelium is usually intact, a finding quite different from that in osseous metaplasia or the retinal pigment epithelium in which case there is no normal RPE in the affected area (1, 2, 3).

Choroidal osteoma has traditionally been managed by observation because no specific treatment was believed to be effective. If subretinal neovascularization threatens vision, laser photocoagulation can be employed to obliterate the neovascularization and prevent extensive hemorrhage (13,14). The visual prognosis is often unpredictable. However, we have observed that if the osteoma is pure orange-yellow in color, the overlying sensory retina is more normal with optical coherence tomography, and if it is subfoveal in location, the vision remains fairly good. In contrast, if the lesion has overlying black patches of RPE proliferation, suggesting spontaneous decalcification, the retina is more damaged and vision is likely to be worse.

These observations may have therapeutic implications. If it were possible to maintain intact bone beneath the fovea or to prevent decalcification from progressing to the fovea, then better vision might be maintained. Methods for achieving this may not yet be available, but it is possible that the use of a barrier laser to prevent progressive decalcification may prove to be of some benefit is preserving better vision. Photodynamic therapy has been recently shown to induce dramatic resolution of a choroidal osteoma and associated choroidal neovascular membrane (53). This method deserves further investigation (53). The associated subretinal neovascular membrane has rarely been removed surgically (20).

Some clinical variations of choroidal osteoma are shown. All patients had ultrasonographic support of the diagnosis, and many also had computed tomography performed, which also supported the diagnosis.

1. Joffe L, Shields JA, Fitzgerald J. Osseous choristoma of the choroid. Arch Ophthalmol 1978;96:1809-1812.

2. Shields JA, Shields CL, DePotter P, et al. Progressive enlargement of a choroidal osteoma. Arch Ophthalmol 1995;113:819-820.

3. Shields CL, Sun H, Demirci H, et al. Factors predictive of tumor growth, tumor decalcification, choroidal neovascularization and visual outcome in 74 eyes with choroidal osteoma. Arch Ophthalmol 2005;123:658-666.

1. Morrison DL, Magargal LE, Ehrlich DR, et al. Review of choroidal osteoma: successful krypton red laser photocoagulation of an associated subretinal neovascular membrane involving the fovea. Ophthalmic Surg 1987;18:299-303.

2. Shields JA, Shields CL, Ellis J, et al. Bilateral choroidal osteoma associated with bilateral total blindness. Retina 1996;16:445-447.

Ancillary studies like fluorescein angiography and OCT have no pathognomonic features in choroidal osteoma, but they can be helpful in detecting choroidal neovascularization and effects of the adjacent, respectively.

Shields CL, Materin MA, Mehta S, et al. Regression of extrafoveal choroidal osteoma following photodynamic therapy. Arch Ophthalmol. In press.

1. Gass JDM, Guerry RK, Jack RL, et al. Choroidal osteoma. Arch Ophthalmol 1978;96:428-435.

2. Williams AT, Font RL, Van Dyk HJ, et al. Osseous choristoma of the choroid simulating a choroidal melanoma. Arch Ophthalmol 1978;96:1874-1877.