Comparing 3 Imaging Systems

The images captured within the 7 standard fields on each camera will be graded using the ETDRS severity scale. The total range of possible scores for severity level is from 10 (no DR) to 80 (PDR with vitreous hemorrhage); higher scores indicate increasing severity.

Details of ETDRS severity scale: 10-No DR, 15-Probable DR, no MAs, 20-MAs only, 35-Mild NPDR, 43,47-Moderate NPDR, 53-Severe NPDR, 60-PDR status post scatter photocoagulation, 61,65,71-PDR, 80-PDR with vitreous hemorrhage, 90,95-Ungradable.

ETDRS level agreement will be cross-tabulated and κ statistics calculated and assessed: <0.20, poor; 0.21-0.40, fair; 0.41-0.60, moderate; 0.61-0.80, substantial; and 0.81-1.00, almost perfect strength of agreement. Unweighted κ will be used to avoid potential bias by weighting. Agreement will also be tested for each severity level and k statistics analyzed.

The images captured within the 7 standard fields on each camera will be graded using the ETDRS severity scale. The proportion of ungradable images will be documented. On all tests, P < 0.05 will be considered significant, and nonparametric testing will be applied where appropriate.

The images captured on each camera will be graded using the ETDRS severity scale. The total range of possible scores for severity level is from 10 (no DR) to 80 (PDR with vitreous hemorrhage); higher scores indicate increasing severity.

Details of ETDRS severity scale: 10-No DR, 15-Probable DR, no MAs, 20-MAs only, 35-Mild NPDR, 43,47-Moderate NPDR, 53-Severe NPDR, 60-PDR status post scatter photocoagulation, 61,65,71-PDR, 80-PDR with vitreous hemorrhage, 90,95-Ungradable.

ETDRS level agreement will be cross-tabulated and κ statistics calculated and assessed: <0.20, poor; 0.21-0.40, fair; 0.41-0.60, moderate; 0.61-0.80, substantial; and 0.81-1.00, almost perfect strength of agreement. Unweighted κ will be used to avoid potential bias by weighting. Agreement will also be tested for each severity level and k statistics analyzed.

The images captured within the global fields of the Clarus and Optos cameras and the 7 standard field image will be graded using the ETDRS severity scale. The proportion of ungradable images will be documented. On all tests, P < 0.05 will be considered significant, and nonparametric testing will be applied where appropriate.

The images captured on each camera for each participant will be assessed for quality using the Wisconsin Reading Center's 3-step confidence score. 1-High (image can be graded for both 7 field ETDRS and global severity level); 2-Adequate (image cannot be graded for global severity level); 3-Inadequate (image cannot be graded for ETDRS and global severity level).

If Wisconsin Reading Center Confidence score of 2 or 3, a reason is selected (technical, patient, both patient and technical, unknown, or N/A). Eyes with photographs classified as ungradable will be excluded from agreement tables.