Hyperoxic myopia: a case series of four divers.

Hyperoxic myopia is a phenomenon reported in individuals who have prolonged exposure to an increased partial pressure of oxygen (PO2) and subsequently have a myopic (nearsighted) change in their vision. To date, there are numerous accounts of hyperoxic myopia in dry hyperbaric oxygen treatment patients; however, there have been only three confirmed cases reported in wet divers. This case series adds four confirmed cases of hyperoxic myopia in wet divers using 1.35 atmospheres (ATM) PO2 at the Navy Experimental Diving Unit (NEDU). The four divers involved were the first author's patients at NEDU. Conditions for two divers were confirmed via record review, whereas the other two divers were diagnosed by the first author. All subjects were interviewed to correlate subjective data with objective findings. Each subject completed five consecutive six-hour hyperoxic (PO2 of 1.35 ATM) dives with 18-hour surface intervals. Each individual was within the U. S. Navy Dive Manual's standards for general health. Visual acuity was measured prior to diving. Within three to four days after diving, the individuals reported blurry vision with an associated myopic refraction shift. Each diver had spontaneous resolution of his myopia over the next two to three weeks, with no significant residual symptoms. The divers in this case series were exposed to an increased PO2 (1.35 ATM for 30 hours over five days), a lesser exposure than that in other reports of hyperoxic myopia in wet divers diagnosed with hyperoxic myopia (1.3-1.6 ATM for 45-85 hours in 12-18 days). Furthermore, this pulse of exposure was more concentrated than typically seen with traditional hyperbaric oxygen therapy. Hyperoxic myopia continues to be a risk for those conducting intensive diving with a PO2 between 1.3-1.6 ATM. Additional investigation is warranted to better define risk factors and PO2 limits regarding ocular oxygen toxicity.