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Ultra-widefield fluorescein angiography may help improve treatment in patients with recalcitrant diabetic macular oedema by visualizing areas of peripheral nonperfusion that can benefit from targeted photocoagulation.
To determine this finding, Dr Patel and his colleagues conducted a retrospective, observational case series of patients with recalcitrant DME for a minimal period of 2 years.
All patients underwent ultra-widefield FA with an imaging system (C200 MA, Optos, Dunfermline, UK) and optical coherence tomography (OCT) (Cirrus, Carl Zeiss Meditec, Jena, Germany) on day 1 of the study.
Before the ultra-widefield FA images were obtained, patients received a standard intravenous infusion of sodium fluorescein. The macular thickness was measured on spectral domain-OCT images.
The mean outcome measures were the mean ischaemic index, mean change in the central macular thickness (CMT), and mean number of focal photocoagulation treatments applied to the macula over the 2-year study.
Patients with recalcitrant DME were divided into 4 cohorts based on the severity of their DR:
The mean overall ischaemic index in all patients was 47%, Dr Patel noted. The mean ischemic indexes based on the severity of the DR were 0%, 34%, 53% and 65%, respectively.
The mean respective decreases in CMT values were 25.2%, 19.1%, 11.6% and 7.2%, and mean number of application of focal photocoagulation were 2.3, 4.8, 5.3 and 5.7.
Disseminating the results
The investigators commented that areas of retinal vascular nonperfusion that are untreated may be associated with recalcitrant DME and the study results supported that premise, in that 80% of patients with recalcitrant DME in this study had evidence of untreated nonperfusion.1
"Calculating the ischaemic index allowed us to quantify nonperfusion and place a ratio of nonperfused to perfused retina," he said. "Our results demonstrate that the most recalcitrant DME existed in patients with the largest areas of retinal nonperfusion. As a result, these patients had the least amount of reduction in the CMT, requiring the greatest amount of macular photocoagulation treatments."
Dr Patel underscored the role of ultra-widefield FA in visualizing the pathology in the peripheral retina in patients with DR, and said he believed that detection and delineation of areas of retinal vascular nonperfusion may be clinically valuable.
"The association between retinal capillary nonperfusion and recalcitrant DME found in this study supports the hypothesis that zones of untreated retinal nonperfusion may stimulate production of biochemical mediators leading to recalcitrant DME and a suboptimal response to therapeutic treatments," he said. "Therefore, ultra-widefield FA may be a valuable tool to identify therapeutic target areas for photocoagulation, allowing for efficient treatment of ischaemic retina and potentially decreasing the production of vascular endothelial growth factor and cytokines that play a role in recalcitrant DME."
1. R.D. Patel et al., Am. J. Ophthalmol., 2013;155:1038–1044.