Date of Award

1994

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

First Advisor

John T Thompson, M.D.

Abstract

Air travel is known to be potentially hazardous for patients with intraocular gas bubbles (IGBs). These bubbles, which are used in the treatment of complicated retinal detachments, can last for up to a month depending on the combination of long-acting gases used. We hypothesized that the external pressure changes associated with hyperbaric oxygen therapy, SCUBA diving, or caisson work could be similarly dangerous.

To test this, we placed IGBs into the right eyes of 18 rabbits and exposed them to several hyperbaric pressure profiles. In all profiles, the intraocular pressure (IOP) in the left or control eyes remained constant while the IOP in the eyes with the IGB dropped to zero on pressurization and increased to over 50 millimeters of mercury (mmHg) on depressurization. Pressures in excess of 50 mmHg were sustained for 10 minutes or longer. The mean peak IOP of the eyes with the IGBs as well as the mean time spent at an IOP of over 50 mmHg were both highly significant compared to that of the control groups (p<0.001).

This IGB-induced IOP response is caused by several mechanisms including continued vitreous and aqueous fluid inflow with decreased outflow during hypotony, bubble volume increase due to equilibration with higher partial pressures of oxygen and nitrogen, and choroidal engorgement with delayed draining at high IOPs. The magnitude and duration over 50 mmHg of the IOPs measured were enough to potentially cause severe pain, occlusion of the central retinal artery, and retinal ischemia. We therefore strongly advise against hyperbaric exposure for patients with IGBs.

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