Cheers to Eric, his family, and his clinical team, and thanks for inspiring us to look into the medical literature on this subject. Hyperbaric oxygen is now indicated for the treatment of central retinal artery occlusion (CRAO), a kind of stroke of the eye, a vascular event requiring speedy attention. Proper treatment in the first 24 hours is critical. Until today's news we had not heard of any longer-term use of hyperbaric oxygen to preserve or restore eyesight or prevent blindness.
About HBOT for Leber hereditary optic neuropathy, the International Foundation for Optic Nerve Disease (IFOND) says:
The sparse negative anectodal evidence of Hyperbaric Oxygen Therapy [HBO] treatment specifically in LHON is not encouraging. This is not currently a line of active research in LHON. HBO has been suggested as a treatment by delivering increased levels of oxygen to the affected nerve cell during its "starvation" period, or period of onset of blindness. A counter argument is that too much oxygen may be toxic in the context of poor cell antioxidant functioning. Oxygen toxicity to the eye is a known problem in premature babies on oxygen. There has been some success, however, using HBO with with other nerve diseases.
This paragraph does not sound like the work of someone who has made a serious study of the hyperbaric medical literature. A quick search for "optic AND neuropathy AND hyperbaric" yields 8 entries in the Rubicon Research Repository and 33 papers on PubMed. We better get reading.