Background/aims— Digital imaging is widely used for diabetic retinopathy screening. The storage and transmission of digital images can be facilitated by image compression. The authors aimed to assess the e V ect of image compression on the accuracy of grading diabetic retin- opathy. Methods —Forty nine 35 mm transparen- cies (17 with no retinopathy, eight with background, five with preproliferative, and 19 with proliferative retinopathy) were digitised and subjected to JPEG compression by 90%, 80%, 70%, and 0%. The 196 images were randomised and graded on a portable computer. Two masked graders assessed the images for grade of retinopathy and image quality (0–10). The sensitivity and specificity of retinopathy grading were calculated with a weighted kappa for grading agreement between levels of compression. Results —The sensitivity of retinopathy grading was reduced by JPEG compression. At 90%, 80%, 70%, and 0% compres- sion the sensitivities were 0.38, 0.50, 0.65, and 0.72, respectively; the specificity re- sults were 1.00, 1.00, 0.83, and 0.84, respectively; and the weighted kappa scores were 0.60, 0.75, 0.77, and 0.84, respectively. The quality scores for 90%, 80%, 70%, 0% compression were 2.9 (SD 1.1, 95% CI; 2.7–3.2), 4.6 (SD 1.1, 95% CI; 3.0–5.6), 5.8 (SD1.5, 95% CI 5.0–6.6), 6.3 (SD1.4, 95% CI; 5.4–7.2) (p<0.01 for each intergroup comparison).
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PUBLICATION RECORD
- Publication year
1993
- Venue
Diabetes Care
- Publication date
1993-05-01
- Fields of study
Not labeled
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