Shortcomings and pitfalls of ocular MRI.

MRI was performed in 41 patients with ocular lesions: 27 cases of malignant melanoma, 5 of haemorrhage, 3 of choroidal metastasis, 3 of senile disciform macular degeneration, 2 retinoblastomas and 1 hamartoma. On MRI 5 small lesions (less than 2 mm thick): 1 melanoma, the 3 metastases and the hamartoma, were not seen. All the malignant melanomas visualised were hyperintense compared to the vitreous on T1-weighted images. On T2-weighted images 24 of 26 lesions were hypointense compared to the vitreous. The remaining two lesions were almost isointense, corresponding to amelanotic lesions. These MRI features did not differ significantly from those of retinoblastomas, senile disciform macular degeneration or subacute choroidal haemorrhage. Major shortcomings of MRI in lesions of the globe lie in a lack of spatial resolution and poor specificity of the findings.