[The sensitivity of computed tomography in the detection of malignant melanomas of the choroid]

193 patients with the ophthalmic diagnosis of a primary choroidal melanoma were studied by computed tomography (CT) in relation to the ultrasound (US) prominence. The location and size as well as the density of the tumour and the vitreous body were measured. The tumour was observed most frequently in the fifth, sixth, and seventh decades of life, with a female preponderance in our series. There was a high correlation between CT and US in the average tumour thickness. But we measured a greater thickness in tumours with US prominence less than 3.5 mm and a smaller thickness in tumours with a US prominence greater than 6 mm. 79% of the melanomas could be distinguished by CT. Especially melanomas with an US prominence of less than 3 mm failed to be detected. The smallest tumour that could be differentiated by CT had a prominence of 2 mm, the largest missed had a prominence of 3.5 mm. In 75% of our contrast CT in patients with 2.5 and 3 mm prominence we could diagnose the tumour, in the noncontrast CT it was only possible in 34%. The enhancement of the vitreous body and the tumour were noted in all patients with contrast CT, the average density increased in the vitreous body for 22% and in the melanoma for 30%. Hence, it is essential to use intravenous contrast media in small choroidal melanomas.