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S Muscat, S Parks, E Kemp, D Keating; The Wide-field Multifocal Electroretinogram and Optical Coherence Tomography in the Assessment of Choroidal Nevi and Melanomas . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1155.
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Purpose: To investigate the potential of the wide-field multifocal electroretinogram (mfERG) and optical coherence tomography (OCT) in differentiating between choroidal nevi and melanomas. Methods: 65 patients presenting with choroidal nevi or melanomas were divided into 4 groups. Group 1: patients with nevi under 2mm in height; Group 2: patients with nevi over 2mm; Group 3: patients with choroidal melanoma pre-treatment at the time of testing; Group 4: patients with choroidal melanoma post-radiation therapy. OCT was performed on all these patients and mfERG was performed on a subgroup of 20 patients. Results: Areas of sub-retinal fluid (SRF), retinal detachments and structural changes in the retina overlying the tumour were clearly shown with OCT even in cases where these were not observed clinically. The mfERG showed delays in P1 latencies in areas corresponding to the tumour site in all patients in groups 3 and 4. The waveform amplitudes were reduced in all but one of these patients. In groups 1 and 2, 6 patients had reduced amplitudes but no delays and 1 patient had delayed P1 latencies at the site of the lesion. Conclusion: Differentiation between benign choroidal nevi and choroidal melanomas presents the clinician with a diagnostic dilemma. A number of clinical factors predictive of growth of small melanocytic tumours have been identified. Amongst these are visual symptoms and the presence of SRF. We have shown that OCT is able to identify SRF before it becomes clinically apparent. The wide-field mfERG can localise areas of retinal dysfunction over the central 90º. This is important in cases where the tumour is peripheral thus patients may be unaware of any associated visual symptoms. mfERG testing showed delayed implicit times with or without reduced amplitudes in all patients with choroidal melanoma and detected abnormalities in several patients with suspicious nevi. Our study indicates that OCT and wide-field mfERG can identify two of the risk factors associated with growth of suspicious nevi before they become clinically apparent. A long-term study to establish the risk of growth associated with early detection of SRF and abnormalities on the mfERG is required.
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