Stability of 35-mm scanners as used in ophthalmologic research.

BACKGROUND AND OBJECTIVE To assess the consistency of digitization of 35-mm slides as practiced in ophthalmologic research and estimate the impact of variation on semi-automated retinal vessel width measurements. PATIENTS AND METHODS A single retina slide was repeatedly digitized under various conditions on three scanner models. Average color levels were extracted from the resulting images, from which vessel widths were graded. The color channel level variations and possible correlation with width were analyzed. RESULTS The Nikon 5000 scanner (Nikon Corp., Tokyo, Japan) had average coefficients of variation of 0.4, 2.3, and 0.5 for the red, green, and blue channel levels across all runs. The P values of the correlation between the red, green, and blue color channel levels and the width of the large retinal arteriole were .89, .27, and .58, respectively. CONCLUSION The results suggest that the tested scanners digitize the 35-mm slides in a reliable manner without biasing the retinal vessel measurements.