Choroidal osteomas are rare benign calcific masses of the globe.
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Epidemiology
Choroidal osteomas are typically found in young Caucasian women 1. A number of familial cases have been reported 3.
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 1,3.
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 6.
Blue-light fundus autofluorescence (bAF)
Relatively well spared 6.
Pathology
Choroidal osteomas are composed of mature bone including marrow like spaces. They are located in the peripapillary choroid 1,3.
Their aetiology remains unknown. Some consider them to be benign neoplasms 1. Others define them as choristomas, whilst others still think of them as secondary ossification of another underlying process (e.g. trauma, inflammation) 3.
Radiographic features
Choroidal osteomas are typically unilateral (in around 75% of cases 7) 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 echogenic foci, with acoustic shadowing.
CT
Calcific curvilinear regions on the posterior aspect of the globe, usually sparing the optic disc.
MRI
Reported signal characteristics include 5
- 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 3. They may be complicated by choroidal neovascularisation which may lead to loss of vision, and in such cases photocoagulation therapy may be of benefit, although overall response is poor 3. Some publications report a benefit with intravitreal bevacizumab 9.
History and etymology
The term ‘choroidal osteoma’ was coined by Gass in 1978 9.
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 2
- choroidal melanoma