Hyperbaric oxygen therapy and the possibility of ocular complications or contraindications.

Hyperbaric oxygen therapy increases oxygen pressure and the concentration of reactive oxygen species in blood and tissues. Increased oxygen pressure may be beneficial in some diseases, such as in the treatment of diabetic leg ulcers and diabetic retinopathy; however, due to their cytotoxic properties, an excess of reactive oxygen species in tissues and/or deficiencies in antioxidant activity, may contribute to complications of hyperbaric oxygen therapy, such as cataract. This review examines the possibility that increased tissue concentrations of reactive oxygen species may also exacerbate other ocular diseases. For example, reactive oxygen species and deficiencies in antioxidant activities contribute to the pathogenetic processes in keratoconus. Such impact may be exacerbated by exposure to additional reactive oxygen species during hyperbaric oxygen therapy. The senescent eye may be particularly prone to oxidative damage as exemplified by conditions such as macular degeneration and cataract. Because of its high consumption of oxygen, the retina is particularly susceptible to oxidative stress, which plays a major role in retinopathy. For example, under normal conditions age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelial cells. Hyperbaric oxygen therapy may exacerbate these processes. In addition to cataract, age-related macular degeneration and keratoconus, there may be other ocular diseases for which exposure to hyperbaric oxygen therapy-related oxidative stress may be significantly adverse. In all such cases, careful pre-examination and evaluation of the potential risk and benefit from this form of therapy appears to be warranted. Unless it could interfere with the benefits of hyperbaric oxygen therapy, antioxidant dietary supplementation may be indicated in conjunction with any hyperbaric oxygen therapy, when there are co-existing diseases for which oxidative stress could have significantly adverse side effects. Delivery of hyperbaric oxygen therapy may need to be modified or it may even be contraindicated in these cases.