Identification of individual microaneurysms: a comparison between fluorescein angiograms and red-free and colour photographs.

Abstract

To evaluate how often a microaneurysm (MA) seen in a fluorescein angiogram (FAG) is visualized in colour or red-free photographs, and conversely how often a red dot seen in a colour photograph or a red-free photograph is found in an FAG as an MA. Sixty-degree FAGs, colour photographs and red free fundus photographs of 24 patients with mild background retinopathy were analysed using a computer-assisted fundus lesion localization system. Only lesions identified similarly in two separate sessions were processed further. The presence of lesions identified by their position was compared in FAGs and colour and red-free photographs. In the whole material 394 MAs were detected in FAGs, 95 in red-free and 62 in colour photographs. Of the MAs in FAGs 26 (6.6%) were seen as a red dot in a colour photograph and 52 (13%) were found in red-free photographs. Of the 95 MAs found in red-free images 52 (55%) were detected in FAGs. Of the 62 MAs in colour photographs, 26 (42%) were seen as a MA in a FAG. A significant correlation existed between MA counts in FAGs and red dot counts in colour or red-free photographs of individual patients. Although MAs in FAG and red spots in colour or red-free photographs all reflect the degree of retinopathy, about half of the red dots in photographs do not represent open MAs in FAGs.