Validation of mobile-based funduscope for diabetic retinopathy screening in Estonia

Aim: To validate mobile-based funduscope for diabetic retinopathy screening in Estonia. Methods: Quality validation comparison of HEINE(R) iC2 funduscope and Zeiss Visucam camera with image scoring and diagnostic test accuracy measurement by sensitivity and specificity. Study took place from January 2020 until March 2020 in East-Tallinn Central Hospital's eye clinic. Results: Based on 90 patients, the Zeiss Visucam showed 35.6% DR prevalence while iC2 had 18.9% for images and 17.8% for videos. The average Likert score was 4.7 for Zeiss Visucam and 2.4 for both iC2 images and iC2 videos. The sensitivity of iC2 images was 72.7% (95%CI 49.6-88.4) for grader 1 and 61.9% (95%CI 38.7-81.0) for grader 2, iC2 video sensitivity was 57.1% (95%CI 37.4-75.0) and 65.4% (95%CI 44.4-82.1), respectively. The grader-based specificity for iC2 images was 96.7% (95%CI 80.9-99.8) and 93.5% (95%CI 77.2-98.9). iC2 videos had a 100% (95%CI 91.7-1.0; 92.0-1.0) specificity by both graders. Cohen's kappa agreement was 0.82 and 0.96 for images and videos. Conclusion: Mobile-based funduscope iC2 is not valid for DR screening with non-dilated pupils and thus not suitable for clinics that do not have experienced specialist present. Moreover, the screening specialist needs to be experienced fundus photographer with extra multiple day training for funduscope use. As main resolution, mobile-based funduscope was not validated for DR screening in Estonia based on pre-set study criteria. Additional research and development of funduscope algorithm for image stripping from videos is needed for validation as iC2 benefits do not offset the gold standard at the moment.