TLDR

Central retinal artery occlusion (CRAO) is a true ocular emergency — often called the "stroke of the eye." Retinal cells begin dying within minutes of arterial blockage. Hyperbaric oxygen therapy (HBOT) must begin within 24 hours of symptom onset to offer the best chance of visual recovery, with treatment ideally starting within the first 6 to 12 hours. HBOT is an FDA-approved indication for CRAO, covered by Medicare and most PPO insurance plans. OxygenWell in Los Angeles (Sherman Oaks and Calabasas) accepts urgent CRAO referrals from ophthalmologists, emergency physicians, and urgent care providers throughout the greater Los Angeles area, including evenings and weekends. Call (818) 661-0939 for urgent physician-to-physician coordination.

Table of Contents

• What Is Central Retinal Artery Occlusion?
• Why CRAO Is Called the "Stroke of the Eye"
• The Critical 24-Hour Time Window
• How Hyperbaric Oxygen Therapy Works in CRAO
• FDA Approval and Insurance Coverage for CRAO
• The HBOT Protocol for CRAO
• Who Should Be Referred — and When
• Physician-to-Physician Referral at OxygenWell
• Why Referring Physicians Choose OxygenWell for CRAO
• Frequently Asked Questions

What Is Central Retinal Artery Occlusion?

Central retinal artery occlusion (CRAO) occurs when the central retinal artery — the primary blood supply to the inner layers of the retina — becomes suddenly blocked, most commonly by an embolus, thrombus, or vasospasm. The result is acute, complete ischemia of the inner retina: a loss of oxygen and glucose delivery to tissue with one of the highest metabolic demands in the human body.

CRAO typically presents as sudden, painless, profound monocular vision loss — often described by patients as a curtain falling over one eye, a dramatic dimming, or complete blackout of vision on one side. Unlike many eye conditions, there is no pain, no redness, and no warning. The onset can happen within seconds.

CRAO affects approximately 1 to 2 per 100,000 people annually. It most commonly occurs in individuals over 60, and risk factors closely mirror those of cerebrovascular and cardiovascular disease: hypertension, atrial fibrillation, carotid artery disease, diabetes, hyperlipidemia, and smoking. CRAO carries significant systemic implications — up to 25% of patients have a concurrent cerebrovascular event, making neurological evaluation and urgent imaging essential alongside ocular assessment.

The ophthalmoscopic hallmark of CRAO is a pale, edematous retina with a classic "cherry-red spot" at the fovea — where the choroidal circulation provides a brief window of preserved perfusion that contrasts sharply against the ischemic surrounding tissue. This finding alone should trigger immediate emergency protocols.

Why CRAO Is Called the "Stroke of the Eye"

The comparison to stroke is not rhetorical. CRAO shares the same pathophysiology, the same urgency, and nearly the same cellular death cascade as acute ischemic stroke of the brain — except that retinal neurons are even more metabolically unforgiving.

The retina is among the highest oxygen-consuming tissues in the body. When the central retinal artery is occluded, the inner retinal layers deplete their local oxygen reserves within 60 to 90 seconds. Irreversible cell death in the ganglion cell layer — the nerve fiber layer responsible for transmitting visual signals to the optic nerve — begins within 4 to 6 minutes of complete ischemia. By 90 to 100 minutes of sustained occlusion without treatment, the damage becomes permanent and global.

The phrase "time is tissue" — the driving principle behind stroke triage — applies here with equal force. Just as brain tissue loses approximately 1.9 million neurons per minute during ischemic stroke, the retina undergoes its own rapid, irreversible cellular collapse during arterial occlusion.

What distinguishes CRAO from stroke, however, is the absence of a well-established acute reperfusion protocol equivalent to IV tPA in cerebrovascular stroke. Traditional management attempts — ocular massage, anterior chamber paracentesis, carbogen inhalation, intraocular pressure reduction — have shown limited and inconsistent efficacy. This is precisely where hyperbaric oxygen therapy fills a critical and evidence-supported clinical gap.

As the NIH/PMC literature on CRAO as a retinal stroke makes clear, the condition demands the same urgency protocols as cerebrovascular events — and referral pathways for HBOT must be built into every emergency ophthalmology and ER workflow.

The Critical 24-Hour Time Window

The evidence is consistent and compelling: HBOT initiated within the first 24 hours of CRAO symptom onset offers the greatest chance of meaningful visual recovery. Within that window, earlier is always better. Multiple clinical studies and the recommendations from the Undersea and Hyperbaric Medical Society (UHMS) and the American Heart Association both point to the first 6 to 12 hours as the optimal intervention window.

Why does time matter so specifically?

During the first several hours after arterial occlusion, some retinal cells remain in a state of penumbra — metabolically compromised but not yet irreversibly dead. These are the cells that HBOT targets. By dramatically increasing dissolved oxygen in plasma (independent of red blood cells or hemoglobin), HBOT can deliver oxygen to ischemic retinal tissue via the intact choroidal circulation — bypassing the blocked central retinal artery entirely.

A 2021 PMC study on HBOT for CRAO confirmed that patients treated within 24 hours consistently demonstrated better visual acuity outcomes than those treated later. A retrospective analysis published in Cureus further confirmed improved visual function in patients receiving early HBOT. The American Academy of Ophthalmology's editors' choice review, "Early Hyperbaric Oxygen Therapy After CRAO May Enhance Visual Recovery," highlights the promising impact of early intervention.

Importantly, an emerging 2026 case report from the University of Pécs Medical School explored HBOT initiated beyond 24 hours and still demonstrated meaningful visual improvement in select patients — suggesting the therapeutic window may have more nuance than a hard cutoff. However, this does not diminish the urgency of early referral. The sooner treatment begins, the more retinal tissue can be salvaged.

Clinical implication for referring providers: Any patient presenting with sudden painless monocular vision loss within the last 24 hours — from any emergency department, ophthalmology office, or urgent care center — is a candidate for urgent HBOT referral. Do not wait for imaging confirmation to make the call.

How Hyperbaric Oxygen Therapy Works in CRAO

To understand why HBOT works in CRAO when other treatments often fail, it is essential to understand the physics of oxygen delivery under pressure.

Under normal atmospheric conditions, oxygen is carried almost entirely bound to hemoglobin in red blood cells (RBCs). Dissolved oxygen in plasma — free oxygen molecules carried directly in the blood fluid — accounts for only about 0.3 mL of O2 per 100 mL of blood at sea level. When the central retinal artery is blocked, RBC-bound oxygen cannot reach the ischemic inner retina regardless of how much oxygen the patient breathes — the delivery pathway is simply interrupted.

HBOT changes the equation entirely. At 2.0 to 2.4 ATA of pressure, breathing 100% medical-grade oxygen increases dissolved plasma oxygen to approximately 4.4 to 6.0 mL per 100 mL of blood — a 14 to 20-fold increase over baseline. This dissolved oxygen does not require functioning red blood cells or an open artery to reach target tissue. It diffuses directly through plasma and tissue fluids, following oxygen tension gradients, reaching ischemic retinal cells via the intact choroidal circulation that supplies the outer retinal layers.

In CRAO, this mechanism accomplishes several simultaneous therapeutic goals:

• Maintains retinal cell viability: Dissolved plasma oxygen keeps the penumbral zone of partially ischemic retinal tissue alive while the occlusion is being addressed through other means, effectively extending the treatment window and buying critical time.
• Reduces ischemia-driven edema and inflammation: HBOT downregulates pro-inflammatory cytokines (TNF-alpha, IL-1beta, IL-6), reducing the secondary inflammatory cascade that accelerates irreversible retinal damage following the initial ischemic event.
• Supports angiogenesis in surrounding microvasculature: With sustained HBOT, vascular endothelial growth factor (VEGF) activity and CD34+ stem cell mobilization support the budding of new microvascular networks in the peri-ischemic retinal tissue — improving collateral perfusion over the course of treatment.
• Reduces reperfusion injury: When blood flow is eventually restored, HBOT pre-conditions the tissue by upregulating endogenous antioxidant enzymes — superoxide dismutase (SOD), glutathione — that neutralize the reperfusion injury cascade.
• Preserves mitochondrial function: HBOT directly supports mitochondrial respiration in oxygen-deprived cells, maintaining energy production even in the setting of vascular compromise.

The net result: HBOT does not simply add more oxygen. It reroutes oxygen delivery around the blocked vessel, protects at-risk tissue from death, and creates a cellular environment that supports recovery rather than collapse.

A systematic review and meta-analysis comparing HBOT to intravenous thrombolysis for CRAO, published in the Journal of Clinical Medicine (MDPI, 2026), found that HBOT demonstrated favorable visual outcome improvements, particularly when initiated early — reinforcing the case for HBOT as a frontline adjunct treatment in the acute CRAO management pathway.

FDA Approval and Insurance Coverage for CRAO

Central retinal artery occlusion is one of 14 FDA-approved, on-label indications for hyperbaric oxygen therapy recognized by the Undersea and Hyperbaric Medical Society (UHMS) and covered by Medicare and most commercial PPO insurance plans.

This matters enormously for referring providers and patients alike:

• HBOT for CRAO is not experimental or off-label — it carries the same insurance-coverage standing as HBOT for diabetic wounds, radiation injuries, or carbon monoxide poisoning.
• Medicare Part B covers HBOT for CRAO when appropriate documentation of the diagnosis is provided — including funduscopic findings, visual acuity testing, and documentation of onset time.
• Most PPO plans follow CMS guidelines and similarly cover CRAO-indicated HBOT.
• At OxygenWell, a dedicated billing team handles all pre-authorizations — reducing the administrative burden on referring practices and ensuring patients begin treatment as quickly as possible.

The American Heart Association has classified HBOT as a Level IIb recommendation for CRAO — indicating that treatment is reasonable and that the benefit likely outweighs risk based on available evidence. Given the lack of other highly effective acute treatments and the low risk profile of HBOT when administered in a properly equipped, physician-directed facility, the risk-benefit calculation strongly favors initiating HBOT promptly in eligible patients.

The HBOT Protocol for CRAO

OxygenWell follows the UHMS-recommended hyperbaric protocol for central retinal artery occlusion:

In the acute phase — within the first 24 to 72 hours — sessions may be scheduled twice daily when clinical urgency and patient tolerance allow, as the goal is to provide continuous tissue oxygenation while the ischemic event is still partially reversible. As the acute window passes, treatment transitions to once-daily sessions to support angiogenesis, reduce residual inflammation, and consolidate whatever visual recovery has been achieved.

OxygenWell operates FDA-cleared monoplace chambers rated to 2.4 ATA — the full therapeutic pressure range for CRAO. Many HBOT facilities operate at only 1.3 to 1.5 ATA, which is insufficient for the dissolved oxygen levels required for effective CRAO treatment. Our high-flow medical-grade oxygen delivery system ensures that dissolved plasma oxygen reaches the therapeutic threshold at every session.

Who Should Be Referred — and When

Any patient presenting with the following profile warrants immediate consideration for urgent HBOT referral:

• Symptom: Sudden, painless, monocular vision loss — complete or near-complete
• Onset: Within the last 24 hours (patients within the first 6 to 12 hours are highest priority)
• Examination: Fundoscopic findings consistent with CRAO — pale retina, cherry-red spot, attenuated arterioles, optic disc pallor
• Exclusions: No active contraindications to HBOT (assessed during intake)

The referring diagnosis does not need to be confirmed by fluorescein angiography or OCT before the referral call is made. Clinical presentation and fundoscopy are sufficient to initiate the referral process. If the time window is tight, call first and confirm imaging concurrently.

Do not wait for:

• Fluorescein angiography results
• Spontaneous visual improvement (which rarely occurs and does not negate HBOT benefit)
• Standard "watch and wait" protocols that are not appropriate for this time-sensitive diagnosis
• Insurance pre-authorization to be completed before referral (our billing team handles this in parallel with treatment initiation when urgency requires it)

Patients who have already trialed other conservative CRAO treatments — ocular massage, carbogen inhalation, anterior chamber paracentesis — without meaningful visual improvement are still candidates for HBOT within the appropriate time window. HBOT works through a distinct and complementary mechanism and does not preclude concurrent management.

Physician-to-Physician Referral at OxygenWell

OxygenWell maintains a dedicated urgent referral pathway specifically for time-sensitive vascular emergencies, including CRAO. Referring physicians can expect:

• Direct physician coordination: Dr. Beth Meneley and our clinical team are available for direct physician-to-physician consultation on urgent cases.
• Same-day treatment capability: OxygenWell offers extended hours including evenings and weekends — a critical advantage for CRAO cases that present outside standard business hours, when most other HBOT facilities in Los Angeles are unavailable.
• Insurance and billing handled for you: Our dedicated billing team manages all Medicare and PPO pre-authorization submissions, reducing friction in the referral process.
• Clinical documentation and follow-up: We provide referring physicians with comprehensive treatment records, session-by-session clinical notes, and outcome documentation for continuity of care.
• Two convenient Los Angeles locations: Sherman Oaks and Calabasas — serving the entire greater Los Angeles area, San Fernando Valley, Ventura County, and surrounding communities.

To initiate an urgent CRAO referral, call our direct physician line: (818) 661-0939. For non-urgent referrals or general clinical inquiries, visit www.oxygenwell.com.

Why Referring Physicians Choose OxygenWell for CRAO

Selecting the right hyperbaric facility for a time-critical CRAO referral requires more than geographic proximity. The quality of treatment — the pressure rating, oxygen delivery system, clinical oversight, and operational hours — directly affects patient outcomes. OxygenWell was built to meet the highest clinical standards for exactly these situations.

FDA-Cleared to the Full 2.4 ATA

CRAO requires 2.0 to 2.4 ATA to achieve the dissolved plasma oxygen levels needed to perfuse ischemic retinal tissue. Many HBOT centers in Los Angeles operate low-pressure chambers rated only to 1.3 to 1.5 ATA — inadequate for CRAO. OxygenWell's monoplace chambers are FDA-cleared and routinely operated at 2.0 to 2.4 ATA for all on-label indications.

Medical-Grade Oxygen Delivery

OxygenWell uses a high-flow medical-grade oxygen supply system — not a standard 10-liter oxygen concentrator. This distinction is critical for achieving therapeutic dissolved oxygen levels at depth. The difference in clinical efficacy between a concentrator and a proper medical-grade delivery system is significant, particularly for high-metabolic-demand conditions like CRAO.

Physician-Owned and Physician-Led

California law requires hyperbaric facilities to be physician-owned. OxygenWell is founded and led by Dr. Beth Meneley, DAOM, L.Ac., with 25+ years in integrative medicine and 12+ years dedicated specifically to hyperbaric medicine in Los Angeles, overseeing more than 50,000 supervised HBOT sessions. Our care team includes Certified Hyperbaric Oxygen Technicians (CHTs), most of whom are EMT-certified, with a Physician Assistant on-site most weekday hours.

Extended Hours — Including Evenings and Weekends

CRAO does not follow business hours. OxygenWell's expanded schedule — including evenings and weekends — means that a patient presenting to your ER or office on a Saturday afternoon still has access to urgent HBOT within the critical treatment window. This is rare among HBOT centers in the Los Angeles area.

Insurance and Medicare Accepted

As a fully credentialed, insurance-approved facility that meets all FDA and UHMS safety and medical oversight standards, OxygenWell accepts Medicare and PPO insurance for all FDA-approved HBOT indications, including CRAO. Our billing team manages every pre-authorization, so neither the referring provider nor the patient faces administrative barriers to timely treatment.

Frequently Asked Questions About HBOT for CRAO

Can hyperbaric oxygen therapy restore vision after central retinal artery occlusion?

Yes — when initiated within the critical time window (ideally within 6 to 12 hours, and up to 24 hours of symptom onset), HBOT can preserve or partially restore visual function in CRAO patients by delivering dissolved plasma oxygen to ischemic retinal cells through the intact choroidal circulation. The degree of visual recovery depends on how quickly treatment begins, the completeness of the initial occlusion, and the patient's baseline retinal health. Earlier treatment consistently produces better outcomes in published clinical literature.

What does hyperbaric oxygen therapy feel like for CRAO patients?

Patients lie comfortably inside a monoplace chamber wearing a clear non-rebreather oxygen mask and breathe 100% medical-grade oxygen during the 90 to 120-minute session. The chamber pressurizes gradually to 2.0 to 2.4 ATA. Most patients experience mild ear pressure during ascent and descent — similar to descending in an airplane — which resolves with simple equalization techniques. Our Certified Hyperbaric Technicians remain in direct contact with patients throughout every session.

Is HBOT for CRAO covered by Medicare?

Yes. Central retinal artery occlusion is an FDA-approved, on-label indication for hyperbaric oxygen therapy, and Medicare Part B covers HBOT for CRAO when clinical documentation meets coverage criteria — including fundoscopic findings, documented visual acuity, and symptom onset within the appropriate time window. Most commercial PPO plans follow Medicare's coverage framework. OxygenWell's billing team manages all pre-authorization submissions.

How quickly can OxygenWell begin CRAO treatment after referral?

For urgent CRAO referrals made during our operating hours, our goal is to have the patient in the chamber on the same day as referral. Call (818) 661-0939 directly for urgent physician-to-physician coordination. OxygenWell's evening and weekend availability means we can accept referrals when most other HBOT centers in Los Angeles are closed.

What if the patient presents more than 24 hours after CRAO onset?

While the strongest clinical evidence supports treatment within 24 hours, emerging case reports demonstrate that some patients treated beyond that window still achieve meaningful visual improvement — particularly in cases of incomplete occlusion or preserved partial flow. We encourage referring providers to call and discuss the specific clinical scenario. We will assess the case on its individual merits and advise on whether treatment is appropriate.

Can HBOT be combined with other CRAO treatments?

Yes. HBOT is fully compatible with concurrent medical management of CRAO, including ocular massage, anterior chamber paracentesis, intraocular pressure lowering, and systemic anticoagulation when indicated. HBOT works through a distinct mechanism — dissolved plasma oxygen delivery — and does not interfere with pharmacological or procedural interventions. For patients who have not responded to initial conservative measures, HBOT represents a distinct therapeutic pathway that should be added, not substituted.

Does HBOT treat both eyes, or only the affected eye?

HBOT is a systemic treatment — the patient breathes 100% oxygen at pressure, which saturates the plasma throughout the entire body. Both eyes receive the benefit of elevated dissolved oxygen during each session, though the therapeutic intent in CRAO is directed at rescuing ischemic tissue in the affected eye. No localized application or device placement on the eye is needed.

Act Now — Every Minute Matters

Central retinal artery occlusion is one of the few vision-threatening emergencies where a single phone call at the right moment can make the difference between permanent blindness and meaningful visual recovery. The science is clear: hyperbaric oxygen therapy, initiated rapidly, delivers oxygen where the blocked artery cannot — and retinal cells that would otherwise die remain viable long enough to recover.

OxygenWell exists to be the clinical partner that Los Angeles ophthalmologists, emergency physicians, neurologists, and urgent care providers call when time is critical.

Urgent CRAO Referrals: (818) 661-0939
Physician-owned. FDA-cleared to 2.4 ATA. Medicare and PPO insurance accepted.
Sherman Oaks and Calabasas, CA. Evening and weekend availability.
www.oxygenwell.com

About the Author

Dr. Beth Meneley, DAOM, L.Ac. is the founder of OxygenWell Hyperbaric and Regenerative Medicine Center in Sherman Oaks and Calabasas, California. With 25+ years in integrative medicine and 12+ years dedicated to hyperbaric medicine in Los Angeles — overseeing more than 50,000 supervised HBOT sessions — Dr. Meneley is one of the most experienced hyperbaric clinicians in the region. OxygenWell is a physician-owned, insurance-approved facility operating FDA-cleared chambers at the full therapeutic pressure range for all UHMS-recognized HBOT indications.

This article is intended for healthcare professionals and informed patients. It is not a substitute for individualized medical evaluation and treatment. Urgent clinical decisions regarding CRAO should be made in consultation with a qualified hyperbaric physician.