Measurements of linear dimensions on fundus photographs: comparison between photographic film and digital systems.

Abstract

The aim of this study is to compare linear fundal landmarks measurements of standard photographic film with colour digital fundal images. Pairs of fundus fluorescein images were acquired with a digital system and photographic film on 10 patients. Each pair of images was assessed independently by two observers who calculated the distance between two selected points on each image using easily identifiable landmarks. Measurements made using film images were compared to measurements made using the corresponding digital images. Agreement between the two methods of measurements was assessed using a linear correlation and graphical method. The patients were divided into two groups based on the field setting on the digital software. In Group 1, the correlation coefficient was 0.99 and in Group 2 it was 0.98, indicating a high level of agreement between measurements with the computer measuring tool for digital images compared to photographic films using a standard reticule. On the basis of the strong correlation between linear fundal landmark measurements between standard photographic film and colour digital fundal images, we conclude that the measurements from the digital images are acceptable for diagnostic and therapeutic purposes. Although there was a tendency for the measurements to be less accurate with increasing distances measured.