Choroidal osteoma (osseous choristoma): an atypical case. A case of choroidal osteoma presenting in a 22-year-old girl is reported. The tumour, unilateral and in a juxtapapillary site, appeared markedly elevated on the retinal plane, not flat or slightly elevated as in previous reports. Visual acuity was not affected, and there was a complete absence of subjective symptoms. Echography, fluorangiography, computerised tomography, and visual field tests were performed. Echography is the best method for identifying and differentiating this lesion from a malignant tumour. 