Digital fluorescein fundus angiography with DFC-512 and IMAGEnet systems

Image processing with direct acquisition digital fundus fluorescein angiography using the OIS DFC-512 and Topcon IMAGEnet were assessed. Fundus diseases included central and branch retinal vein occlusion, diabetic retinopathy, age-related macular degeneration, central serous choroidopathy and angioid streaks. Analogue images were taken with Kodak Tri-X 35 mm film as well. Although the resolution of the original image was less than that of 35 mm film, it was improved by image processing, particularly contrast enhancement. One type of contrast enhancement, available in both systems, exaggerated lack of light at the peripheral area of the original image. This drawback was not seen with another type of enhancement processing, available in IMAGEnet. However, the latter produced an artificial hypofluorescent area around an intensely hyperfluorescent lesion and also exaggerated hyper- and hypo-fluorescent patches of the background. Nevertheless, these processing methods were particularly useful in case of media opacity like cataract, even when the 35 mm film picture is not clear. Other processing techniques like pseudocolor and relief, etc. were used just for different ways of presentation. The two systems are basically equivalent, except for contrast enhancement. There was no problem for diagnosis in both systems, but the artificial effects must be borne in mind when interpreting the image.