The effect of normobaric hyperoxia in a radiation retinopathy case study
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Abstract
Background: Radiation retinopathy is a progressive ocular disease that is a common complication following exposure to ionizing radiation. Despite current treatments, some patients continue to lose vision due to retinal ischemia and retinal edema, necessitating further investigation into therapeutical alternatives. Pilot studies of supplemental oxygen and hyperoxia therapy have recently demonstrated improved outcomes in vision and reduction of symptoms in ocular disorders involving diseases of the retinal vasculature such as diabetic retinopathy and retinal vein occlusion. Hyperbaric oxygen therapy (HBOT) has been reported to improve complications associated with radiation retinopathy, but HBOT poses challenges regarding affordability and availability of hyperbaric chambers. Normobaric hyperoxia (NBH) therapy presents a more cost-effective and accessible alternative that has been successfully shown to ameliorate edema and improve visual outcomes in retinopathies with similar clinical presentations as radiation retinopathy and thus may be an effective treatment for complications due to radiation retinopathy. Objective: In this case study, we investigated whether administration of NBH could reduce retinal edema and improve visual acuity in a patient with retinal edema and vision loss associated with radiation retinopathy. Methods: Three patients with radiation retinopathy were initially screened for NBH treatment. Of those, one patient proceeded with treatment and completed two 3-hour NBH sessions and one 3-hour normobaric normoxia (NBN) session which served as a control. Before and after each session, best corrected distance visual acuity (VA) was assessed using Early Treatment Diabetic Retinopathy Study testing, and retinal thickness was imaged using optical coherence tomography. Retinal thickness measurements were taken at five points along the area of edema and average differences and percent changes in thickness were calculated. A student’s one-tailed t-test was used to analyze statistical significance. Results: Retinal thickness in the area of edema was reduced by an average of 27±7.14 µm with an average percent change in thickness of 4.35±1.01%, and VA improved from 20/63-2 (LogMAR=0.54) to 20/63+1 (0.48) after the first NBH trial. After the second NBH trial, retinal thickness in the area of edema was reduced by an average of 20.2±2.59 µm with an average percent change in thickness of 4.42±0.58%, and VA was improved from 20/50 (0.4) to 20/32-1 (0.22). Following the NBN control session, retinal thickness was reduced by an average of 5.8±0.84 µm and had a percent change of 1.71±0.23% with relatively little change in VA. Retinal thickness was found to be significantly reduced following each NBH trial when compared to NBN measurements (p = 0.001 and 0.0002). Conclusion: In a patient with radiation retinopathy, NBH treatment demonstrated improved outcomes in VA and reduction of retinal edema. Addition of NBH therapy to existing disease management plans may expand the treatment repertoire for patients suffering from radiation retinopathy and lend further support for the use of NBH therapy as a treatment option for additional ophthalmic disorders.
Description
2021