Retinal video recordings at different compression levels: a novel video-based imaging technology for diabetic retinopathy screening

Background To evaluate the optimal compression level of retinal color digital video recordings, a novel video-based imaging technology, in screening for diabetic retinopathy (DR). Design Evaluation of a diagnostic technique. Methods A total of 36 retinal videos, captured using EyeScan (Ophthalmic Imaging System), were compressed from original uncompressed file size of 1GB (gigabyte) to four different compression levels-100MB (megabyte) (Group 1); 30 MB (Group 2); 20 MB (Group 3); and 5 MB (Group 4). The videos were subsequently interpreted by an ophthalmologist and a resident using the International Clinical Diabetic Retinopathy Severity Scales. Main outcome measures The sensitivity, specificity and kappa coefficient for DR grading detected by were calculated for each compression level (Groups 1-4), with reference to the original uncompressed retinal videos. Results Groups 1, 2, and 3 graded by both readers had sensitivity and specificity >90% in detecting DR, whereas for group 4, the sensitivity and specificity were 70.6% and 94.7% for ophthalmologist and 80.0% and 72.2% medical officer, respectively. The kappa correlation in detecting DR for groups 1, 2, and 3 were >0.95, whereas for Group 4, the kappa was 0.76 and 0.66 for ophthalmologist and medical officer, respectively. Conclusion Retinal video recording is a novel and effective DR screening technique with high sensitivity, specificity and kappa correlation. With its compressibility, this is a potential effective technique that can be widely implemented in a routine, mobile, and tele-ophthalmology setting for DR screening services.