In vivo micropuncture of retinal vessels

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Abstract
Micropuncture has proven to be a valuable tool for the local study of vascular parameters in many organ systems; however, it has not been applied to the study of the circulation of the retina. We report here our extension of micropuncture techniques [4] to use in the intact retina of the anesthetized cat. We use extremely sharp micropipettes with tip sizes much smaller than the diameter of erythrocytes to avoid hemorrhage. The micropipette is held by a microdrive which in turn is mounted on a precision goniometric micromanipulator. We micropuncture retinal arteries and veins with diameters ranging from 20 to 130 μm with no apparent damage to the vessel wall and no observed hemorrhage. During micropuncture we routinely inject nanoliter quantities of dyed saline, which we observe flowing in a plume from the micropipette tip within the lumen of the vessel. Micropuncture techniques may be used in the laboratory to study retinal autoregulatory mechanisms by microinfunsion of vasoactive substances and by measuring blood pressure in retinal microvessels. In the clinic micropuncture may be useful for treating disorders such as retinal vascular occlusion.