Hyperbaric Oxygenation and the Eye

Researchers in Italy are reporting a breakthrough treatment for retinitis pigmentosa with the use of hyperbaric oxygen therapy. Daily hyperbaric oxygen at 2.2 atmospheres of pressure was employed among 24 RP patients for two years. The electroretinogram readings of RP patients undergoing hyperbaric oxygen treatment improved from 4.86 at the beginning of the study to 14.4 at the end of the study. RP patients who did not undergo oxygen therapy experienced diminished electroretinograms, beginning with an average of 4.92 decreasing to 2.97. Hyperbaric oxygen therapy may rescue retinal photoreceptors. This report provides encouraging news to RP patients since there is no proven treatment for RP save for vitamin A therapy which only slows down progressive loss of vision as measured by an electroretinogram and does not improve the ERG.

K.K. Jain, author of The Textbook of Hyperbaric Medicine, indicates the retina has the highest rate of oxygen consumption of any organ in the body. That hyperbaric oxygen treatment is helpful in cases of RP is an anomaly because it has been shown to cause severe constriction (narrowing) of retinal blood vessels. The hallmark of RP is poor retinal circulation. The constriction of the retinal blood vessels however is offset by the greatly increased oxygen carrying capacity of the blood during treatment (oxygen saturation increases by 23 percent).

Contrast Sensitivity
(Undersea & Hyperbaric Medicine 21; 387-90, 1994)

Hyperbaric oxygen treatment improves contrast sensitivity (ability to see shades of gray) when administered to healthy volunteers. Even though patients with non retinal eye disorders have experienced constriction of retinal blood vessels following hyperbaric oxygen treatment, when there is a lack of oxygen supply to the retina narrowing of retinal blood vessels does not occur.

Other Reports
(New England Journal of Medicine 281; 25-30, 1969)
(Journal French Ophthalmology 10: 381-86, 1987)

The medical literature reveals that hyperbaric oxygen treatment has been tried on cases of retinitis pigmentosa as early as 1965. A 1987 report in the Journal of French Ophthalmology indicates hyperbaric oxygen treatment improved the visual acuity of a patient with retinitis pigmentosa and macular edema.

Radiation neuritis, optic nerve
(Ophthalmology 93; 1083-88, 1986; Journal Clinical Neuro-ophthalmology 113; 98-101, 1993)

Hyperbaric oxygen treatment has been used as a rescue remedy for optic nerve damage caused by radiation treatment for brain tumors.

Hyperbaric oxygen improved vision among individuals who experienced a sudden loss of vision due to diminished blood supply to the optic nerve. Oxygen therapy must be administered early following onset of the event before shrinkage of the optic nerve occurs. (Arh Hig Rada Tokaikol 45; 19-24, 1994)

Decreased Vision due to multiple sclerosis
(New England Journal Medicine 308; 181-86, 1983)

Multiple sclerosis patients undergoing 20 hyperbaric oxygen treatments experienced temporary improvement of their symptoms including visual symptoms.

Recently 100 percent oxygen delivered at 2 times atmospheric pressure did not produce a significant improvement in visual acuity or peripheral vision among patients suffering from a condition known as non arterial anterior ischemic optic neuropathy. (American Journal Ophthalmology 122; 535-41, 1996)

Glaucoma

Among glaucoma patients, hyperbaric oxygen has been shown to expand peripheral vision, an effect which lasted for 3 months. (Acta Ophthalmologica 71; 315-19, 1993)

The fluid pressure in the eye of humans and animals decreases as atmospheric pressure is raised in a hyperbaric chamber. (Investigative Ophthalmology 19; 43-48, 1980)

K.K. Jain, author of Textbook of Hyperbaric Medicine, reports that hyperbaric oxygen has been used to
successfully treat cases of glaucoma. Twenty or more 90 minute treatments at 2 atmospheres of pressure expanded the visual field among all glaucoma subjects tested. There was no change in eye fluid pressure.

Retinal artery and vein occlusion

Hyperbaric oxygen treatment combined with a blood vessel widening drug (vasodilator) has been shown to improve visual function among individuals experiencing retinal artery occlusion. (European Journal Ophthalmology 3; 89-94, 1993)

Hyperbaric oxygen treatment has been successfully used to improve vision among patients with retinal swelling (macular edema) and retinal vein occlusion. (Survey of Ophthalmology 39; 347-66, 1995)

Hyperbaric oxygen treatment has been administered successfully to patients with central retinal swelling (macular edema) resulting from retinal vein occlusion. Among 12 patients who were treated, 10 experienced visual improvement, with median visual acuity improving from 20/100 to 20/25. The hyperbaric oxygen treatment is believed to constrict retinal capillaries and thus decrease leakage of fluid that causes edema. (Ophthalmologica 210; 168-170, 1996)

Ocular side effects HBO2

It has been known that healthy persons can breathe oxygen at 3 times normal atmospheric pressure for 3 hours without any ocular side effects, but during the fourth hour some begin to experience a narrowing of their visual field.

One reported side effect of hyperbaric oxygen treatment is the development of myopia (nearsightedness). (Journal Hyperbaric Medicine 1; 69-73, 1987) Myopia was first reported in 1978 among 18 of 26 patients undergoing hyperbaric oxygen treatment at 4 atmospheres of pressure. (Transactions American Ophthalmology Society 76; 118-24, 1976) Note: Italian doctors only used 2.2 atmospheres of pressure in their successful treatment of RP with hyperbaric oxygen.

Dogs exposed to 3 atmospheres of pressure at 100 percent oxygen developed retinal problems and a reduction in their electro-retinograms. Narrowing of the visual field and impairment of central vision has been recorded among humans undergoing hyperbaric oxygen treatment at 3 atmospheres of pressure for more than 4 hours. (Science 151; 466-68, 1966)

Captain Frank K. Butler, Jr. of the U.S. Navy reviewed the ocular effects of hyperbaric oxygen treatment in a recent issue of Review of Ophthalmology. Hyperbaric oxygen may induce myopia (nearsightedness) at the rate of one quarter diopter change in eyeglass prescription per week among patients receiving daily hyperbaric oxygen treatment. The myopia reverses slowly over a course of many weeks. Cataracts have been reported to occur among patients undergoing a prolonged course of daily hyperbaric oxygen treatment which may not be reversible following cessation of treatment, particularly among adults of advanced age. (Survey of Ophthalmology 39; 347-66, 1995) K.K. Jain indicates cataracts may occur among patients undergoing hyperbaric oxygen treatment but that these were seldom observed when less than 200 treatments were administered.

K.K. Jain reports that the most useful role of hyperbaric oxygen in eye care is the relief of blood vessel constriction in central retinal artery occlusion with a success rate as high as 60 percent. Hyperbaric oxygen does not appear to have a useful role in the treatment of diabetic retinopathy. K.K. Jain states “With the pressure and duration of exposures used in clinical practice, ocular complications are not a problem… Hyperbaric oxygen appears to be a safe treatment from the ocular point of view.” Confirming its safety, hyperbaric oxygen treatment has been applied in cases of multiple sclerosis with optic neuritis without loss of vision or narrowing of the visual field.

AUTHOR

Ernest S. Campbell, M.D., FACS

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