have performed a further analysis on 36 retinal videos for compression to evaluate the compression time and diagnostic accuracy of compressed retinal videos in detecting any grade of DR using the video compression software, Xilisoft Video Converter Ultimate 6.0, and all videos were also viewed on 27-in. iMac (Apple, USA).

4.2.1Main Outcome Measures

We evaluated the sensitivity, specificity, and Kappa statistics of retinal video recording and retinal still photography in detecting any grade of DR and sight-threatening DR, with reference to slit lamp examination by a consultant ophthalmologist. In addition, we also evaluated the technical failure rate, defined as the proportion of ungradable retinal videos and retinal images, for retinal video recording and retinal still photography, respectively. In addition, we compared the sensitivity, specificity, and Kappa statistics for the compressed retinal videos at 20 and 5 MB in diagnosing DR grading, with reference to the uncompressed retinal videos.

4.3Results

Of the 100 patients (200 eyes), the mean age of participants, duration of diabetes, and HbA1c were 13.7 ± 15.1 years, 13.7 ± 9.7 years, and 8.0 ± 1.7%, respectively. About 70% of patients were Caucasian and had type II diabetes. Eighteen eyes (9%) had cataracts diagnosed on slit lamp examination. Table 4.2 shows the number of

Table 4.2 The diabetic retinopathy severity level of the participated eyes (total eyes = 200)

patients with different DR severity levels. As expected, more patients suffered more microvascular complications than macrovascular complications with diabetic neuropathy (20%) being the leading cause of all, followed by diabetic nephropathy (20%), and other macrovascular complications such as ischemic heart disease (16%), peripheral vascular disease (10%), and cerebrovascular disease (6%).

4.3.1Retinal Video Recording Versus Retinal Still Photography

For retinal video recording, both ophthalmologists had sensitivity and specificity of more than 90% in detecting any grade of DR, with reference to the slit lamp examination (ophthalmologist 1: sensitivity

– 94%, specificity – 99%; ophthalmologist 2: sensitivity – 93% and specificity – 95%). Similarly, the sensitivity and specificity of retinal still photography were also more than 90% for both of the readers (ophthalmologist 1: sensitivity – 92%, specificity – 98%; ophthalmologist 2: sensitivity – 92%, specificity – 97%). In detection of sightthreatening DR, both imaging methods had 100% sensitivity and specificity as graded by both ophthalmologists. On the other hand, the Kappa coefficient for retinal video recording and retinal still photography in diagnosing DR grading and lesions (microaneurysms, retinal hemorrhages, cotton wool spots, intraretinal microvascular abnormalities, new vessels formation, venous beading, and hard exudates) were all more than 0.80.

4.3.2Video Compression Analysis

With the video compression analysis, the sensitivity and specificity of the 20 MB group was shown to be 94.4% and 100%, respectively, by ophthalmologist and 100% and 93.8%, respectively, for the medical officer. On the other hand, the sensitivity and specificity of the 5 MB compressed retinal videos were 70.6% and 94.7%, respectively for ophthalmologist and 80% and 72.2% for medical officer. The conversion timing for a retinal video from 1 GB to 20 MB took approximately 20 s.