Arroyo JG, Seto B, Yamada K, et al. - In the present study, the researchers sought to examine the impacts of a relatively inexpensive, non-invasive, short-term treatment with low-dose normobaric hyperoxia (NBH) on macular edema in patients with retinal vein occlusion (RVO). Participants with RVO-associated macular edema were treated for 3 h with 5 LPM of NBH via facemask (40% fraction of inspired oxygen, FIO2). Patients who had a second NBH treatment 1 month later experienced a recurrence of their edema, but showed a similar significant decline in MMT and CMT following the second NBH treatment. Three-hour therapy with 40% FIO2 NBH results in substantial reductions in MMT and CMT. This research demonstrates an ischemic mechanism for macular edema associated with retinal vein occlusion.