The Tele-Screening Model for Diabetic Retinopathy: Evaluating the Influence of Mydriasis on the Gradability of a Single-Field 45° Digital Fundus Image

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Abstract
The purpose of this article was to study the influence of pupillary dilatation on the gradability of a single-field 45° digital fundus images taken in a telescreening model for diabetic retinopathy. Telescreening camps for diabetic retinopathy were organized in rural south India. Sixty-eight patients with type 2 diabetes were enrolled. Single-field 45° digital fundus images were obtained before (group I) and after pupillary dilatation (group II). Digital fundus images were obtained using nonmydriatic fundus camera and transmitted in real time to the base hospital for grading by a retinal specialist. Various factors that could influence the gradability of images were studied, including patients' age and visual acuity, experience of the photographer, and interobserver variability. After pupillary dilatation, the nongradability of digital fundus images was reduced from 29.1% to 8.6%. With each line of improvement in Snellen's Visual acuity, the gradability improved by 12.1%; likewise, with each year of age, the gradability improved by 5.5% following mydriasis. Interobserver variation was excellent (k = 0.88). The learning curve of photographer had no effect on image gradability. Pupillary dilatation improves the gradability of a single-field 45° digital fundus image during telescreening of diabetic retinopathy.