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Abstract
Because of the small blood flow and unusual vascular distribution patterns, it is difficult to measure blood flow directly through the arteries and veins of the eye. The ophthalmoscopic technique of reflective densitometry avoids these problems by measuring blood flow through the pupil in a known portion of the eye. Normal values of flow and volume have been determined as have changes with different experimental conditions. The advantages of the method may be summarized. First, it does not require surgical intervention anywhere near the eye. The eye is left in a relatively undisturbed state during the measurements. Second, continuous monitoring of the choroidal blood volume is made. Then, multiple measurements of blood flow can be made which require very short sampling times. Finally, the exact area being studied is known. The chief limitation of the method is the maximum of about five serial measurements of blood flow that are possible for each experiment. Other problems arise from the necessity for rigidly supporting the animal and his eye to align the optical bench properly. In these experiments we have extended ophthalmoscopic studies of the posterior pole of the eye to obtain quantitative information about its vascular layers. The usefulness of this approach has been demonstrated by the experiments performed which investigate the reactivity of the choroid