Abstract
Abstract: :
Purpose: To define arc-pattern nasal retinal ischaemia on fluorescein angiography (FFA) and explore its temporal relationship with development of proliferative diabetic retinopathy (PDR) Methods: We analysed FFA of 30 Type 2 diabetic eyes with peripheral retinal ischaemia in 4 quadrants. Areas of ischaemia were identified when crossing arterioles and venules stained in late-venous phase angiograms. Tracing disc and main vessels on to overlaid acetate sheets created a retinal montage of each eye and the posterior limit of vessel staining was marked on the montage. This produced a centripetal arc-pattern around the disc in the nasal retina. The anterior limit of the arc was marked if present. The best fit 'centre' of the posterior arc was determined by comparison with overlaid concentric circles and distance from arc to nasal disc was measured in disc diameters (dd). The onset of subsequent PDR in these eyes was determined from clinical records. Results: All eyes that developed PDR within a year of the FFA date (n=8) had nasal retinal ischaemia almost up to (<1dd) the disc margin. Those developing PDR within 1-2years (n=11) had 1-2dd of nasal retina between posterior limit of ischaemia and disc and in both these groups the arc-pattern centred on the optic disc. One eye developed PDR after 4 years' follow up with 2+ dd arc distance. In the remainder (n=10), PDR had not developed an average of 1.7 years (range 1-4y) since the FFA. Although the majority had arc distances 1 - 2dd from the disc, 3 of these non-proliferative eyes had ischaemia within1dd of the nasal disc margin. Conclusion: We report an observed trend between proximity of retinal ischaemia to the nasal disc margin and onset of PDR in Type 2 diabetes. If this simple formula were to be validated by larger numbers, it would be a useful guide for planning prophylactic and macular laser treatment. Although the majority of eyes examined conformed to the observed trend, the exceptions warrant further analysis to try to identify local and systemic features that may have delayed onset of PDR.
Keywords: 448 ischemia • 523 proliferation • 388 diabetic retinopathy