Hyperbaric and transcorneal delivery of oxygen to the rabbit and monkey anterior segment

When delivered to the corneal surface of rabbits for 30 minutes, 100% oxygen can significantly increase the mean (± SD) partial pressure of oxygen (PO₂) in the aqueous humor (from 63.5 ± 12.3 mm Hg [n = 12] to 139.5 ± 32.4 mm Hg [n = 8]). Similar elevations were seen in monkeys. Under hyperbaric conditions (2 atm) for 30 minutes the aqueous PO₂ in rabbits breathing room air can be increased to 295.2 ± 132.4 mm Hg (n = 7) by exposing the rabbit cornea to 100% oxygen for 30 minutes. The high PO₂ under these hyperbaric conditions is mediated by both vascular and transcorneal delivery of oxygen. The increase of PO₂ in the rabbit aqueous can prevent or reverse sickling of intracameral human erythrocytes containing sickle hemoglobin. The exposure of rabbit eyes to 100% oxygen at the corneal surface is followed by autoregulation (constriction) of the iris vasculature. Transcorneal or vascular delivery of oxygen to the eye under normobaric or hyperbaric conditions may possibly benefit patients with hypoxic diseases of the anterior segment such as anterior segment necrosis, rubeosis iridis, or sickle cell hyphema.