A young diver develops temporary nearsightedness (myopia) after repetitive, shallow, no-decompression air dives.
Reported Story
An otherwise healthy and fit 23-year-old male diver completed the last of seven dives over a five-day period. All dives were under the supervision of an experienced divemaster with a reputable dive center. All dives were on compressed air only and no deeper than 78 fsw (24 msw) for less than 50 minutes in duration.
On the day of the incident, he dived at 9 a.m. and again at 1 p.m. During a debriefing at 3 p.m., he complained of a visual disturbance and mild temporal headache. The visual symptom manifested as a slow, progressive impairment of distance vision, while near vision remained normal. The symptom persisted; the next day after consulting with a physician on the DAN Emergency Hotline, he took a 75-minute flight back home.
Two days after symptom onset he was examined extensively by an ophthalmologist, who documented significant myopia of 2.50D. After dilating the pupils with cyclopentolate, the myopia reduced to approximately 1.25D. No other ocular or neurological pathology was found. All symptoms resolved slowly without treatment, and uncorrected distance acuity exceeding 20/20 (normal) was recorded four days after accident.
Retinal tomography demonstrated subtle changes to the internal limiting membrane. This test was to be repeated in a week to see if it had normalized.
Comment
I am an ophthalmologist, and I was with this diver, who lives in the same city as I do. I did a very basic clinical assessment at the dive site when his visual symptoms persisted for more than 24 hours.
He is normally emmetropic (normal sharp focus) with 20/20 uncorrected distance acuity. When I first tested his vision he achieved near normal acuity, but he experienced drastically diminished distance vision. This was confirmed by one of my associates back home the following day: 20/200 uncorrected acuity, which could be corrected to 20/20 with a myopic prescription of about -2.50 in both eyes.
The diver returned home by air to go back to work, while the rest of the group continued the dive trip, only returning home two days later. Upon my return, I re-examined him on the fifth day to find that he had fully recovered. The change in vision affected both eyes equally and was not accompanied by any neurological symptoms or signs except for a dull headache in the temporal area, which resolved as his vision and myopia returned to normal. I was satisfied that the headache was accounted for by spasm of ocular muscles trying to achieve accommodation, which is also described in reports on hyperoxic-induced myopia (HIM). This was confirmed by significantly reduced myopia after administering medication to dilate his pupils for in-depth examination.
Thus, it has been verified that the visual disturbance in this case was one of induced myopia, identical to the HIM described in numerous reports on the effects of hyperoxia. However, we have no reason to suspect hyperoxia in this case as only air was used and partial pressure of oxygen during the dive was not high enough. Decompression sickness was also not likely because the dives were quite conservative.
Additional testing after the diver’s vision recovered showed that the retina was normal and that there was no central neurological damage.
I am intrigued by the incident and will continue to search for an explanation. More important, we are happy that the diver has recovered fully. We advised him to take special care on future dives.
Michael Schultz
Additional Reading
Butler Jr. FK; White E; Twa M (1999). Hyperoxic myopia in a closed-circuit mixed-gas scuba diver