Central Retinal Artery Occlusion
Central retinal artery occlusion (CRAO) is a sudden, painless loss of vision caused by obstruction of the central retinal artery and, although infrequent, can cause permanent visual loss. CRAO is the most recently approved indication by the Undersea and Hyperbaric Medicine Society (UHMS) for HBOT. CRAO is caused by the obstruction of the central retinal artery and, although an infrequent cause of visual loss, leads to permanent visual loss.
Current treatment for CRAO consists of attempts to lower intraocular pressure and movement of a potential embolus downstream, ocular massage, anterior chamber paracentesis, and medications (both eye drops and oral). Most modalities have proven inefficacious.
A small study by Hertzog et al evaluated HBOT with CRAO. Patients were divided into groups based on time of onset of CRAO to HBOT. The study noted that HBOT was most useful in preserving vision if instituted within eight hours.
Another retrospective study published by Beiran compared patients from a facility where HBOT was available to a facility that did not have HBOT. The patients who received HBOT demonstrated visual improvement (82% HBOT vs 29.7% control).
Patient selection for HBOT should meet the following criteria: Less than 24 hours of painless vision loss, no history of flashes or floaters prior to vision loss, visual acuity 20/200 or worse, even with pinhole testing, age older than 40 years, and no recent eye surgery or trauma. Visual improvement has been reported even with delay of HBOT.
HBOT is administered at two ATA on 100% oxygen. If no response is noted, pressure should be increased to 2.8 ATA. If vision is still not improved after 20 minutes, US Navy treatment Table 6 is indicated. If vision is improved, continue at treatment depth for 90 minutes bid. Continue daily bid compression until resulting in three days without visual improvement. If the patient responds to 100% oxygen via nonrebreather (NRB) mask itself, HBOT is not needed, and the patient should be maintained on surface 100% oxygen for 12 hours.