Choroidal osteomas

Choroidal osteomas are rare benign calcific masses of the globe.

Epidemiology

Choroidal osteomas are typically found in young Caucasian women . A number of familial cases have been reported .

Clinical presentation

These lesions are usually unilateral (75%), and result in painless and gradual visual loss, although in some instances rapid central visual loss may occur .

Fourier-domain optical coherence tomography (FD-OCT)

FD-OCT imaging may show a distinctive latticework pattern of reflectivity resembling the spongy bone structure seen histopathologically.

Blue-light fundus autofluorescence (bAF)

Relatively well spared .

Pathology

Choroidal osteomas are composed of mature bone including marrow like spaces. They are located in the peripapillary choroid .

Their etiology remains unknown. Some consider them to be benign neoplasms . Others define them as choristomas, whilst others still think of them as secondary ossification of another underlying process (e.g. trauma, inflammation) .

Radiographic features

Choroidal osteomas are typically unilateral (in around 75% of cases) and located on the posterior wall of the globe, near, but usually not involving, the optic disc. They are calcified and plaque-like.

Ultrasound

Plaque-like echogogenic foci, with acoustic shadowing.

CT

Calcific curvilinear regions on the posterior aspect of the globe, usually sparing the optic disc.

MRI orbits

Reported signal characteristics include

T1: hyperintense signal
T2: area of relative low intensity
T1 C+ Gd: shows enhancement

Treatment and prognosis

Choroidal osteomas are benign and in many instances (46-60% of cases) remain unchanged in size . They may be complicated by choroidal neovascularization (CNV) which may lead to loss of vision, and in such cases photocoagulation therapy may be of benefit, although overall response is poor . Some publications report a benefit with intravitreal bevacizumab .

History and etymology

The term ‘choroidal osteoma’ was coined by Gass in 1978.

Differential diagnosis

In general the differential is that of other causes of calcification of the globe including:

drusen
- usually smaller
- located at the optic disc
- usually older individuals
retinoblastoma
- usually a mass with calcification
- protruding into the vitreous body
astrocytic hamartomas
- seen in patients with tuberous sclerosis or neurofibromatosis
- associated with retinal detachment
choroidal melanoma