A comparison between one- and two-field 60° fundus photography when screening for diabetic retinopathy

Abstract

To compare the severity level of diabetic retinopathy obtained when assessed from two versus only one 60 degrees photographic field using colour transparencies and red-free, black-and-white photographs. To compare the areal coverage of these two photographic strategies to that of seven-field 30 degrees photography. Two ophthalmologists graded photographs of 74 eyes of 74 type I and II diabetes patients. Inter-method agreement was expressed in percentages and using kappa statistics and scatter-diagrams. The comparison of the approximate photographic areal coverage was done from diagrams using planimetry. The severity level of retinopathy when judged from two photographic fields was more severe in 13.5% (Grader 1) and in 16.2% (Grader 2) from colour transparencies and in 13.5% (Grader 1) and in 14.9% (Grader 2) from red-free black-and-white prints, as compared to assessments from only one field. Kappa values (0.84-0.86) for inter-method agreement for five pooled retinopathy levels revealed good agreement. Neither grader missed retinopathy requiring clinical assessment or treatment (levels > or = 47) when minimal retinopathy (levels 14-20) was detected using only one 60 degrees colour slide or red-free photograph. A second optic disc-centred field provided valuable additional information when more severe retinopathy lesions (levels > or = 30) were detected in the macula-centred field. One macula-centred 60 degrees photograph covered 60% and two 60 degrees photographs 80% of the area covered by seven-field 30 degrees photography. Two-field 60 degrees photography covers areas left outside seven-field 30 degrees photography. We propose the use of one macula-centred 60 degrees photograph when screening for the first lesions of diabetic retinopathy. After they have been found two-field 60 degrees photography is recommended.