Diagnosis of Uveal Melanoma

Abstract

The diagnosis of uveal melanoma is based on clinical examination with the slit lamp and indirect ophthalmoscope together with ultrasonography of the eye. Large to medium-sized melanomas are reliably diagnosed using these methods. The challenge lies in early detection. Small melanomas are more difficult to tell from presumed naevi. A useful mnemonic 'to find small ocular melanomas' reminds the general ophthalmologist to look for tumour thickness of more than 2 mm, subretinal fluid, visual symptoms, orange pigment and location of the tumour margin at the optic disc. Optical coherence tomography and fundus autofluorescence imaging help in identifying subretinal fluid and orange pigment and in measuring the thickness of thin choroidal tumours. Each of the risk characteristics roughly doubles the likelihood of growth so that the risk for growth is about 30 times higher when all five characteristics are present as compared to their absence. In addition, a low acoustic profile, the absence of a halo around the tumour and the absence of drusen over it increase the likelihood of growth. Patients with a choroidal melanocytic tumour with at least one risk characteristic benefit from referral to an ocular oncologist. We recommend that the rest of the patients be made aware of their presumed naevus and that they should be observed periodically. The patients should also be told to return immediately if they develop new visual symptoms. Finally, the trend is toward taking a biopsy of suspicious small choroidal tumours as an alternative to documenting growth before treating them as melanomas.