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Karl-Johan Hellgren, Boel Bengtsson, Elisabet Agardh; Limits for Perimetric Change Reveal Retinal Sensitivity Deterioration in Diabetic Subjects. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2868.
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New measures are needed to study early retinal damage in diabetic subjects. It takes several years to detect morphological vascular progression of early retinal damage on fundus photographs, today’s gold standard for change. We have created a new strategy to test functional change based on pointwise test-retest variability to detect deterioration of threshold light sensitivities in 24-2 standard automated perimetry (SAP). With this tool we will evaluate perimetry as an outcome measure for early retinal functional damage in diabetic subjects. Here we present the 18 months results of a five-year longitudinal prospective study.
Consecutively recruited diabetic patients with no or mild/moderate diabetic retinopathy are scheduled for examinations every sixth month for three years and than annually up to five years from baseline. A comprehensive examination including SAP and fundus photography is performed at each visit, and fluorescein angiography at baseline and after 3, 4 and 5 years of follow-up. SAP tests are analyzed with our new limits for perimetric change, indicating both significant deterioration and improvement.
Seventy-six out of 81 subjects completed 18 months of follow-up, twelve with type 1 diabetes and 64 with type 2 diabetes. Diabetes duration at this point was 15±12 years (mean±SD), glycated hemoglobin HbA1c 61±12 mmol/mol and 44 subjects were treated for hypertension. The conventional perimetric indices mean deviation and number of significantly depressed points below normal limits had not changed from baseline. Using the new limits, deterioration in more than 5 test points had occurred in 50 % of the subjects, while almost no improvement was seen. Progression of retinopathy, a two step increase according to the Early Treatment Diabetic Retinopathy Study Scale, had occurred in two subjects only.
Despite stable retinal status, we found deteriorated threshold light sensitivity using new limits for perimetric change. Our results suggest that this approach might be used to evaluate functional change, e.g. in clinical trials, but longer follow-up is needed for validation.
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