Evaluation of microvascularization pattern visibility in human choroidal melanomas: comparison of confocal fluorescein with indocyanine green angiography

Background: The presence of specific microvascularization patterns (network s, parallel with and without crosslinking, silent) in histological sections of human choroidal melanomas has prognostic significance for survival. We showed previously in selected patients that the identification of these mic rovascularization patterns is possible in vivo by using confocal scanning l aser indocyanine green angiography and that this technique is superior to f luorescein angiography using a conventional acquisition technique with a fu ndus camera. We now routinely use simultaneous confocal fluorescein/indocya nine green angiography to study microvascularization patterns in choroidal melanomas. The purpose of this study was to compare the visibility of tumor vessels and microvascularization patterns in fluorescein and indocyanine g reen angiography in simultaneous confocal series taken with the same instru ment in a large prospective series of patients. Patients and methods: The simultaneously procured confocal fluorescein and indocyanine green angiograms of 50 patients with untreated choroidal melano mas (maximal apical height according to standardized A-scan between 2 and 8 mm) were studied for the visibility of tumor vessels and microvascularizat ion patterns. At least one simultaneous confocal optical series (32 images in sequential depth order) during the early arterial venous phase was obtai ned per patient. Results: Confocal forescein angiography disclosed signs of tumor vasculariz ation in 12 (24%) of the 50 patients examined. However, in only 3 patients (6%) could microvascularization patterns be identified using confocal fluor escein angiography, and only in the very early arterial phase, which is oft en difficult to capture. In contrast, simultaneously obtained confocal indo cyanine green angiograms disclosed tumor vessels in 47 (94%) of the examine d 50 patients and microvascularization patterns could be identified in all of these cases. In 3 patients (6%) no tumor vessels could be detected withi n the tumor borders. Conclusion: This study demonstrates that confocal indocyanine green angiogr aphy images microvascularization patterns in choroidal melanomas better tha n fluorescein angiography, even when the images are acquired with the same technique. This can be explained with the different absorption, fluorescenc e and exudation characteristics of these dyes. In vivo imaging of these mic rovascularization patterns using confocal indocyanine green angiography off ers the possibility of assessing the prognosis of choroidal melanomas witho ut the removal of tissue.