Hyperbaric oxygen transiently improves visual fields in open-angle glaucoma in a dose-dependent manner.

Clinical Bottom Line:
1. Hyperbaric oxygenation improves visual field but not intra-ocular pressure in open-angle glaucoma.
2. Improvement in fields is shown to ameliorate over six months following treatment.
3. Improvement was dose-dependent over the range 10-30 treatments.
Appraised by: Mike Bennett, Dept of Diving and Hyperbaric Medicine, Prince of Wales Hospital, Sydney; Tuesday, 19 January, 1999

Clinical Scenario: A patient with open-angle glaucoma and restricted visual fields.
Three-part Question: In chronic open-angle glaucoma, does the application of hyperbaric oxygen compared to normobaric air, result in any improvement in visual fields, visual acuity or intra-ocular pressure?
Search Terms: Hyperbaric oxygenation, glaucoma

The Study:
Double-blinded randomised controlled trial with intention-to-treat.
Patients with primary open-angle glaucoma taking regular medication to reduce intra-ocular pressure.
Control group (N = 20; 20 analysed): Usual care with sham treatment at 2ATA breathing 10.5% oxygen to simulate normal air breathing.
Experimental group (N = 91; 91 analysed): Usual therapy plus oxygen at 2ATA for 90 minutes daily for 10 (n=20), 15 (n=20), 20 (n=20) and 30 treatments (n=31)(5 days/week).

The Evidence (using 30 treatment group example):

Non-Event Outcomes Time to outcome Before HBO After HBO P-value

Blind spot (cm2) 6 weeks 0.76 0.52 <0.05
Blind spot (cm2) 6 months 0.76 0.6 >0.05
Visual field
Isopter4 (cm2) 6 weeks 123 135 <0.05
Visual field
Isopter4 (cm2) 6 months 123 131.5 >0.05

Comments:
1. There were no significant changes in visual acuity or intra-ocular pressure across the groups.
2. The two groups were not compared directly, rather they were each compared with their own pre-treatment baseline.
3. There were no statistically significant changes in the control group in terms of fields, blind spot or pressure.
4. The changes in visual field and blind spot areas before and after hyperbaric oxygenation remain statistically significant at 3 months, but not six months.
5. Reduction in blind spot area and improvement in visual field were dose dependent, becoming non-significant at 10 treatments compared to control.
6. The authors recommend 20 treatment course with re-treatment as required.

Expiry date: April 2021
References:
1. Bojic L, Racic G, Gosovic S, Kovacevic H. The effect of hyperbaric oxygen breathing on the visual field in glaucoma. Acta Ophthalmologica 1993; 71:315-319.
2. Bojic L, Kovacevic H, Andric D, Romanovic D, Petri N. Hyperbaric oxygen dose of choice in the treatment of glaucoma. Arh Hig Rada Toksikol 1993; 44:239-247.
3. Bojic L, Kovacevic H, Gosovic S, Denoble P. The effect of hyperbaric oxygen on glaucoma: a prospective study. In: Bakker DJ, Schmutz J, eds. Hyperbaric Medicine Proceedings, 2nd Swiss Symposium on Hyperbaric Medicine. Basel, Switzerland 1990:273-275.



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