Monoplace Delivery System

Monthly Hyperbaric Safety Notice: August 2007

Contact Lenses and Hyperbaric Medicine

Background

The modern use of contact lenses began in the 1950’s when the inner surface of the lens was designed to follow the eye’s shape instead of sitting flat. These early lenses were ‘hard’, i.e. not gas permeable. By 1971, soft (gas permeable) lenses were commercially available in the U.S., and extended wear lenses became available in 1981. Contact lenses are as common today as prescription glasses in adults.

The Issue

It is quite common for contact lens wearers to be referred for hyperbaric oxygen therapy. It is as common for staff members working in multiplace chambers to wear contacts.

There is no restriction on the use or type of contact lens that a patient undergoing hyperbaric oxygen therapy may wear during their treatment. There is an issue with the staff member breathing air in the multiplace chamber, however. This issue relates only to the non-gas permeable (hard) contact lens. As air is breathed at increased pressure, additional nitrogen, accumulates in the tissues. Upon decompression, this nitrogen will leave the body, commonly via the blood and the lung. Nitrogen will also diffuse out through the eye. If the individual is wearing a hard lens, nitrogen will accumulate between the lens and the eye, and bubbles may form. This process (decompression, visual disturbance and the appearance of bubbles) was frequently miss-diagnosed as decompression sickness in the past. Recompression therapy was rendered when all that was required was the removal of the lens.

Bottom Line

No restriction on the use of contact lenses exists for patients undergoing hyperbaric oxygen therapy. This applies to both multiplace and monoplace chambers. Staff members breathing compressed air in multiplace chambers should not use non-permeable lenses. They can use the gas permeable type without any related complication.

Contributing Author: Dick Clarke, CHT

Dick Clarke Dick is President of National Baromedical Services, which he founded in 1986. His previous background included service in the British Royal Navy, diving instructor and underwater photographer, assistant director of the seabed habitat 'HydroLab' and several years in the offshore commercial diving industry. Dick heads the Baromedical Research Foundation where he serves as Principal Investigator for several international clinical trials. He is course director for 'Primary Training in Hyperbaric Medicine' and the 'HBO 2000' series of advanced hyperbaric symposia. Dick has been a NOAA Diving Medical Officer Training Course faculty member since 1983. He pioneered the Certification in Hyperbaric Technology (CHT) program, is a past president of the National Board of Diving and Hyperbaric Medical Technology and remains active at the committee level within the Undersea and Hyperbaric Medical Society.

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