A Study of Retinal Venous Blood Oxygen Saturation in Human Subjects by Photographic Means

OUR UNDERSTANDING of events in the normal and diseased optic fundus would be aided if it were possible to measure the retinal oxygen tension. The retina has a high rate of oxygen consumption. Its vessels normally change caliber in response to a change in arterial blood oxygen tension, dilating wrhen the tension falls and constricting when it rises." 2 This suggests that shifts in retinal oxygen tension are opposed by appropriate changes in blood flow. In patients with hypertension or diabetes the retinal vessels are generally less responsive to change in arterial blood oxygen.3-5 Some of the retinal changes that occur in these and other disorders, such as hemorrhages, cotton-wool exudates, and neo-vascularization, appear to be caused by retinal hypoxia or ischemia. To facilitate the study of such phenomena we have d'evised a photographic method for estimating in man the per cent oxygen saturation of retinal venous blood, as an index of the over-all retinal oxygen tension. It is the purpose of this report to describe the method and its validation, and to present information obtained from its use in normal subjects. Certain of the early results obtained with early versions of the method have been summarized briefly elsewhere.6 Method

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