Autoregulation of optic-disk oxygen tension.

A micro-oxygen sensor was used to monitor the optic-disk oxygen tension in vivo in the cat. The perfusion pressure of the eye, defined as the systemic arterial blood pressure minus the intraocular pressure, was decreased. This was accomplished both by lowering the systemic arterial blood pressure by increasing the expiratory resistance and by elevating the intraocular pressure. The result of lowering the perfusion pressure of the eye was an initial decrease in the optic-disk oxygen tension and then a return to normal within approximately one minute. This autoregulation of the optic-disk oxygen tension was decreased by hypoxia and eliminated by hypercapnia. It was concluded that this autoregulation is a physiologic adjustment for homeostasis of the optic-disk tissue.