Resolution of nidek 3-dx, zeiss, canon, and topcon fundus cameras.

The limiting factor in resolution in modern fundus photography may be the fundus camera itself. We therefore wanted to measure the ideal resolution of several popular brands of fundus cameras. A standard U.S. Air Force high-contrast resolution test target was photographed in-air with the Nidek 3-Dx, Zeiss FF3, Canon CF-60U, Canon CF-60UV, and Topcon TRC-50X fundus cameras. Resolution was determined after correction for magnification. Resolution was similar on all properly aligned cameras we tested. Presumably because of the fundus camera's prism optics, resolution of vertically oriented targets with all cameras was consistently worse than those directed horizontally. Processing of the simultaneous stereo image from the Nidek 3-Dx camera into a 3.5 x 5-in lenticular transparency (LenTec Corporation, Duluth, GA, U.S.A.) not requiring a stereo viewer caused minor additional degradation in resolution of vertically oriented targets. Fundus camera users may easily check the resolving power of their camera using the method described, to detect deficiencies that could adversely affect the quality of clinical fundus photographs. They should be aware of orientational differences in resolution, especially in lenticular transparencies.