Quantification of retinal damage during cardiopulmonary bypass

Microembolic ischaemia in the retina, as revealed by fluorescein angiography, has been reported during cardiovascular bypass. Subsequent neurological and intellectual dysfunction have also been observed. Since the eye is an outgrowth of the brain it is possible to assume that similar microemboli occur in that organ. By comparison of pre- and end-bypass operation retinal images, an estimate of the damage in terms of the number of vessel occlusions and the areas of non perfusion can be made by expert human observers. The degree of inter- and intra-observer variability is not yet known. Ideally assessments could be made more objective by using digital image analysis, thus facilitating comparisons between different surgical techniques such as different blood oxygenator types. In this paper, the authors present automatic procedures for the enhancement, geometric registration, and location of regions of vascular occlusion