Hyperoxic Myopia: Information for Divers

Exposure to excessive oxygen can impair distance vision.

This phenomenon, called hyperoxic myopia, is a form of oxygen toxicity that affects the lenses of the eyes.1,2 It is a known risk of hyperbaric oxygen treatment (HBO), where oxygen partial pressure (PO2) is 2 to 2.4 Atm,1–10 but also has been documented after exposures to PO2 of 1.3 Atm which is within PO2s traditionally encountered in diving activities.11–14

The first diving-related report of hyperoxic myopia was a case study in an underwater film maker and his partners, with three divers affected.11 Later documented cases occurred at the U.S. Navy Experimental Diving Unit (NEDU) in four divers exposed for six hours per day across five or six days,12, ­13 and in one exposed for four hours per day for five days,12 caisson workers exposed to similar PO2s have also experienced hyperoxic myopia.14 A closer look at the published reports may help divers to assess their own risks.

The underwater film maker11 noticed a general blurriness of vision about 18 days into a 21-day, rebreather dive series in which his exposure totaled 84.8 hours with PO2 of 1.3 Atm. His optometrist confirmed a myopic shift after the end of the dives. Six weeks later his vision had recovered. On his next dive trip he carried an eye chart and checked his vision regularly. He measured changes after nine days and about 36 hours of bottom time. Once again, his vision returned to normal after time. A third dive series of 15 days duration and with approximately 45 hours with a PO2 of 1.3 Atm again caused a temporary myopic shift, a change that also was measured in the diver’s two buddies.

The NEDU dives after which hyperoxic myopia was noted involved six hours per day with PO2 between 1.3 and 1.4 Atm, either for five consecutive days (surface interval 18 hours),12,13 or for six days of diving every other day (surface interval 42 hours).12 The four cases documented with refractive measurement resolved in a few weeks. Other divers with similar oxygen exposure may have been affected, but only subjective measurements, not refraction measurements, were available,12 and approximately 50 other divers underwent six-hour daily exposures for five consecutive days with no measurable changes in visual refraction. After five days with 4-hour exposures (20-hour surface intervals), one of 28 divers had a very small but measurable refraction change after resting in the water,12 but none of 16 divers had measurable refraction changes after exercising during dives.15

Hyperoxic myopia is caused by a change in the angle at which light bends on crossing into or out of the lens tissue in a process similar to that of aging,1, 2, 11 but few other details are known.



1)    Changes can be expected to be self-correcting.

2)    Myopic changes are delayed in onset (for example, four days after the end of a five-day dive series).

3)    Changes in the lens accumulate over repeated dives.

4)    Divers who have age-related stiffening of their lenses, that is, those who need reading glasses, are more likely than younger divers to experience a refractive shift.


Unknown (among many questions):

1)    What is the minimum surface interval to prevent cumulative effects?

2)    Is there a threshold PO2 or exposure time below which hyperoxic myopia does not occur?

3)    Does repeated exposure to elevated oxygen partial pressure influence the age at which a person first needs reading glasses?


Divers who accumulate many hours of bottom time during a dive series, say, more than 20 hours in a week, should be alert for changes in their distance vision. It is probably wise to back off a bit on the oxygen exposure if visual changes are noted. (A myopic shift may also show up as an improvement in near vision without reading glasses.)  But what is your personal acceptable risk? You’ll have to decide!


1.    Khan B., Evans A.W., 2003. Refractive Changes in Patients undergoing Hyperbaric Oxygen Therapy: a Prospective Study [abstract] UHMS meeting abstract,  http://archive.rubicon-foundation.org/1361

2.    Evanger, K., Vaagbø, G., Thorsen, E. and Haugen, O.H., 2011. Phakic and pseudophakic eyes in patients during hyperbaric oxygen therapy. Optometry and Vision Science, 88(6), pp.691-696.

3.    Anderson Jr, B. and Farmer Jr, J.C., 1978. Hyperoxic myopia. Transactions of the American Ophthalmological Society, 76, p.116-124.

4.    Lyne, A.J., 1978. Ocular effects of hyperbaric oxygen. Transactions of the ophthalmological societies of the United Kingdom, 98(1), pp.66-68.

5.    Palmquist, B.M., Philipson, B. and Barr, P.O., 1984. Nuclear cataract and myopia during hyperbaric oxygen therapy. British Journal of Ophthalmology, 68(2), pp.113-117.

6.    Anderson Jr. B. and Shelton D.L., 1987. Axial length in hyperoxic myopia. In: Bove A.A., Bachrach A.J. and Greenbaum L.J. (eds). Underwater and Hyperbaric Physiology IX. Proceedings of the Ninth International Symposium on Underwater and Hyperbaric Physiology. Bethesda, Maryland: Undersea and Hyperbaric Medical Society: 607–611.

7.    Ross, M.E., Yolton, D.P., Yolton, R.L. and Hyde, K.D., 1996. Myopia associated with hyperbaric oxygen therapy. Optometry & Vision Science, 73(7), pp.487-494.

8.    Krott, R., Roessler, G., Heller, R., Krauss, D. and Krieglstein, G.K., 2001, March. Short term hyperbaric oxygenation does not alter ocular refraction (Abstract). In Investigative Ophthalmology & Visual Science (Vol. 42, No. 4, pp. S896-S896). Bethesda, MD, USA: Assoc. Research Vision Ophthalmology Inc.

9.    Fledelius, H.C., Jansen, E.C. and Thorn, J., 2002. Refractive change during hyperbaric oxygen therapy. A clinical trial including ultrasound oculometry. Acta Ophthalmologica, 80(2), pp.188-190.

10. Evanger, K., Haugen, O.H., Irgens, Å., Aanderud, L. and Thorsen, E., 2004. Ocular refractive changes in patients receiving hyperbaric oxygen administered by oronasal mask or hood. Acta Ophthalmologica, 82(4), pp.449-453.

11. Butler Jr, F.K., White, E. and Twa, M., 1999. Hyperoxic myopia in a closed-circuit mixed-gas scuba diver. Undersea and hyperbaric medicine, 26(1), pp.41-45.

12. Shykoff B.E., 2008.Pulmonary effects of submerged oxygen breathing in resting divers: repeated exposures to 140 kPa. Undersea Hyperb Med 35(2):131-143.

13. Brugger J.W., Gupta A., Shykoff B., and Florian J., 2015. Hyperoxic Myopia: A Prospective Study of Twelve Divers with Six Hours of Exposure to 1.35 ATM PO2 for Five Consecutive Days (abstract). Invest. Ophthalmol. Vis. Sci., 56 (7):2176.

14. Onoo, A., Kiyosawa, M., Takase, H. and Mano, Y., 2002. Development of myopia as a hazard for workers in pneumatic caissons. BritisJournal of Ophthalmology, 86(11), pp.1274-1277.

15. Shykoff B.E., 2008. Pulmonary effects of submerged exercise while breathing 140 kPa oxygen. Undersea Hyperb Med. 35(6):417–426.

6 Responses

  1. Julie

    Ironic that this is written on such a hard to read black background/white font

  2. Jeff

    I get hyperopic myopia regularly on trips where we are diving 2 dives a day for approx 2.5hours a dive to an approx depth of 60m on CCRs running set point 1.2 and 1.6 at 6m for our last deco stop – usually 40min or more on pure O2 for 8-10days.
    I am borderline needing glasses and have been for years. I have had it checked out a few times and each time I am barely a 1/4 diopter different but am quite disabled to the point where I have a set of glasses to get me back thru the airports and for about a week thereafter. Eye guy is surprised how disabled I am despite the very minimal changes. Is there another aspect to this other than a lens change or is it a “sudden change” that the brain can’t accommodate to quickly?

  3. Suzanne

    After 38 rebreather dives and 46+ hours dive time over 12 days averaging 17 meters with deepest to 114 meters, I was shocked when I got to airport for flights home and found I could barely make out signage, displays, etc. This blog, some DAN information, and a Duke University Hyperbaric Dive Medicine participant doctor, I now know I have hyperoxic myopia.

    I had a pre-scheduled retina specialist visit 7 days after my last dive for another eye issue related to posterior vitreous detachment — floaters forming but not floating…yet. During this follow-up visit late June 2019 my far vision tested very poorly with my prescription progressive lenses that were deemed providing at least 20/20 correction during first visit in March 2019.

    Thanks to blogs like this I now know what my problem is and can be proactive in following restoration of my vision. I very much appreciate the insights and recommendations Barbara provides. Thanks to Shearwater’s fantastic dive computers and dive data analysis tools, I have detailed records of all the dives, depths, times, gas mixes, CNS, pO2 trends, etc. to use in future to better manage the vision situation.

    Fortunately reading and computer use with my current corrective lenses is working fine. I will follow my progress with visits to my OD. I will share my experience here as I learn more. Thank you Shearwater for hosting such information sharing forums.

    • Shearwater Research

      Hi Suzanne,
      We’re so sorry you developed hyperoxic myopia. We empathize with the challenges the diagnosis entails. We’re happy that our blog was able to lend a resource to you in this difficult time, and we look forward to hearing about your experience as you learn more.

  4. Joseph B

    Great read. Explained what happened to me in July 2019.

    13 days straight CCR Diving.
    Week 1 av depth 40 – 45 mtr dives with 3 dives per day with PPO2 @ 1.2.
    Week 2 av depth 55 – 65 mtr dives with 2 dives per day with PPO2 raised to 1.3 for the last few days as we were doing less dives per day.
    Both weeks av dive time 100 min inc deco.

    Pre trip vision script was + 0.5 for driving and + 2.5 for computer.

    6 days after the last dive I saw my Optometrist. My script on this day was 1.0 for driving (never been a minus) and + 0.75 for reading.

    Vision is expected to sort itself out in a few weeks.

    I hope this data may help those with similar experiences.

    Thanks Shearwater for providing this information.

    • Shearwater Research

      Hi Joseph,
      We’re glad you found this information helpful! Wishing you a speedy recovery!


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