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R. E. Coffee, S. C. Oliver, S. D. Schwartz, T. R. Friberg; The Development of an Ischemic Index for Assessing Diabetic Macular Edema with Scanning Laser Ophthalmoscopic Ultra Wide Field Angiographic Imaging. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5271.
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© ARVO (1962-2015); The Authors (2016-present)
Clinical characteristics have traditionally been used to classify diabetic retinopathy and the risk of disease progression. In an attempt to find angiographic predictors of disease progression, disease severity or likely treatment response, we studied biologically plausible angiographic surrogates of retinal hypoxia, LPVL and capillary non-perfusion. Using ultra wide angle angiography, we measure the extent of late peripheral vascular leakage (LPVL) and capillary nonperfusion in eyes with diabetic retinopathy.
We retrospectively reviewed 10 consecutive ultra wide field digital angiograms (Optos P200A, Dunfermine, Scotland) in eyes with clinically evident diabetic diabetic macular edema. One eye per patient was included in this analysis. We calculated an ischemic index (ISI) for each eye in three ways: 1) by dividing the total area of LPVL observed by the total area of the image; 2 ) by dividing the total area of capillary non-perfusion found on their arteriovenous phase images by the total image area; 3) by adding the area of LPVL and the total area of capillary non-perfusion and dividing the total image area. Digital image analysis was performed using the total pixels showing a given feature by the total number of pixels in the image. No corrections for area artifacts created by imaging device were made.
Eyes with a higher ischemic index demonstrated more extensive capillary dropout, had more extensive late peripheral vascular leakage, and were associated with various stages of diabetic macular edema.
The extent of theoretical retinal hypoxia may be evidenced by an ischemic index. Ideally, a clinically useful ischemic index should represent the percent of the fundus area falling somewhere on the pathological hypoxia-ischemia spectrum. Ultra-wide field fluorescein angiographic findings calculated into an ischemic index are indeed associated with the presence and severity of macular edema. These associations may be due to the retina’s biochemical response to hypoxia, such as upregulation of VEGF. Further studies regarding the predictive value of these indices and the potential to modify treatment strategies need to be validated in prospective clinical trials prior to widespread adoption.
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