Hyperbaric oxygen therapy consists of breathing 100% oxygen continuously or intermittently in a chamber at a pressure equal to or greater than 1.4 absolute atmospheres. Indicated for the emergency treatment of carbon monoxide poisoning and other medical-surgical pathologies such as gas embolism or necrotizing soft-tissue infections, various studies have shown a beneficial effect of hyperbaric oxygen therapy in certain ocular pathologies, notably of microcirculatory origin, such as central retinal artery occlusion or macular edema linked to retinal vein occlusions. In addition, hyperbaric oxygen might represent an alternative treatment for ocular quinine toxicity and might also be useful as an adjuvant to surgery and antibiotics in cases of periorbital necrotizing fasciitis. On the other hand, oxygen in high concentrations has toxic ocular effects due to the production of reactive oxygen derivatives.