Detection of retinal neovascularizations using 45 ° and 60 ° photographic fields with varying 45 ° fields simulated on a 60 ° photograph

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Abstract
To compare the effectiveness of one- and two-field 45 degrees and 60 degrees fundus photography for detection of retinal neovascularizations (NVEs); to compare the detection of NVEs in macular 45 degrees fields centred on the fovea, between the fovea and the disc and with the nasal border along the nasal disc margin with that in standard 60 degrees one- and two-fields. Two ophthalmologists assessed red-free, black and white screening and follow-up photographs of 58 out of a total 72 patients referred for treatment for NVEs over the 3 year period 1997-99. The assessment included analysis of the numbers, sizes and locations of NVEs identified in different photographic fields defined by a transparent grid placed over two standard 60 degrees fields. Testing of 45 degrees macular fields disclosed 59/81 (73%), 50/81 (62%) and 64/81 (79%), respectively, of NVEs detected in a 60 degrees fovea-centred photograph. Kappa values for detecting at least one NVE, when present, were 0.62 (95% CI 0.40-0.83), 0.38 (95% CI 0.19-0.57) and 0.83 (95% CI 0.62-0.99). The corresponding figures when compared with two-field 60 degrees photography were 59/111 (53%), 50/111 (45%) and 64/111 (58%), respectively. One macula-centred 60 degrees field disclosed 81/111 (73%) of NVEs detected by 60 degrees two-field photography with an additional optic disc-centred field. Two-field 45 degrees photography disclosed 86/111 (77%) of NVEs detected by two-field 60 degrees photography. A total of 90% of NVEs detected in the optic disc-centred 60 degrees field only were also detected in the corresponding 45 degrees field. One-field 45 degrees photography cannot be recommended as a screening method for diabetic retinopathy. Two-field 45 degrees photography (macula-centred and disc-centred fields) disclosed 77% of NVEs detected by the corresponding two-field 60 degrees photography.