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A quantitative system to evaluate diabetic retinopathy from fundus photographs
S S Feman1, T C Leonard-Martin, J S Andrews
1Department of Ophthalmology and Visual Sciences, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-8808.
Purpose:
To evaluate a quantitative system to measure the early lesions of diabetic retinopathy seen in stereoscopic fundus photographs.
Methods:
Using a quantitative classification system, photographs of 4657 eyes (7 stereo pairs of 35-mm slides per eye) were scored for 16 diabetic lesions. A single severity level (identical to the ETDRS Interim Scale) was calculated for each eye. The reliability of this technique, and its reproducibility by independent examiners, was evaluated for individual lesions and severity levels using percent agreement, kappa, and weighted kappa statistics.
Results:
This quantitative technique demonstrated an "almost perfect" agreement (weighted kappa > or = 0.810) on all but one lesion by independent observers. For the severity levels, there was a 95.7% perfect agreement (kappa = 0.9428). The reproducibility of agreement over time was "almost perfect" on all but four lesions; with 88% perfect agreement (kappa = 0.8394) for severity levels.
Conclusions:
When used to evaluate the early lesions of diabetic retinopathy, the Vanderbilt Classification System is highly reliable between graders and over time. This system can gather quantitative data and evaluate incremental changes in an accurate, reproducible manner.