Quantification of retinal damage during cardiopulmonary bypass: comparison of computer and human assessment

A comparison of retinal fluorescein angiograms taken before cardiopulmonary bypass with those taken just before the end of operation, has shown that microvascular occlusions can develop during operation. Quantification of the retinal damage in terms of the area of nonperfusion depends on careful examination by humans. Assessment of these areas is necessarily subjective and digital image analysis would be preferable to make the measurements more objective. Visual or automatic comparison of images is facilitated by prior geometrical alignment. A method for registering retinal images which has been used successfully on 65 image pairs is described. Techniques for automatically detecting changes in the microvascular structure are illustrated. Using a subset of 40 good quality image pairs, good agreement between computer detected occlusions and human assessment of nonperfusing areas is reported.<>