Goals of HBOT

• Increase oxygen levels in hypoxic/ischemic inner retinal layers to maintain tissue viability (via oxygen diffusion from the choroidal circulation)
• Prevent retinal edema
• Reduce/prevent ischemia-reperfusion injury if clot obstructing central retinal artery undergoes autolysis
• The artery generally recanalizes within 48 - 72 hours, so HBOT is short-term and based solely on return of vision to the affected eye.
  
  

Diagnosis

• Sudden, painless visual loss, generally unilateral    
• Findings upon fundoscopic exam with dilation:
• • Pale yellow/ white-appearing retina due to ischemia or necrosis 
  • A cherry red spot in the macula (this is finding may not always be present)
• Other physical exam findings may include an afferent pupillary defect (Marcus Gunn pupil) and segmentation of blood in retinal arterioles (boxcarring) 

Hyperbaric Criteria

• Clinical findings suggestive of CRAO, with onset of symptoms within the first 24 hours. However, most patients wake after sleeping to unilateral blindness, and the sooner HBOT is initiated, the better chance to preserve retinal tissue. Best outcomes when HBOT is initiated within 8 hours from onset.

Evaluation

• During workup, deliver 100% supplemental oxygen utilizing a non-rebreather mask
• Past medical history:
• • Patients at risk include those with giant cell arteritis, atherosclerosis, vasospasm, and thromboembolic disease.
  • The presence of "flashes or floaters" preceding vision loss, pain history of recent trauma, or age <40 suggest an alternate diagnosis (retinal detachment/vitreous hemorrhage)
• Physical examination:
• • Visual acuity per ophthalmology should be documented as soon as possible.
  • Intraocular pressure should be measured and treated if elevated but should not delay HBOT
• Labs to order or review: Do not delay HBOT to accomplish any of these.
• 1. Complete Blood Count (CBC) - to screen for platelet disorders or infectious causes
  2. Erythrocyte Sedimentation Rate (ESR)
  3. C-reactive protein (CRP)
  4. Coagulation panel- (fibrinogen, prothrombin time (PT)/ partial thromboplastin time (PTT), antiphospholipid antibody)
  5. Lipid panel
  6. Electrocardiogram (ECG)
  7. Carotid ultrasound
  8. Echocardiography
• For suspected arteritic CRAO, treatment with intravenous corticosteroids should be initiated emergently

Treatment

Treatment should be titrated to patient response as follows:  

• Start with hyperbaric oxygen therapy at 2.0 ATA oxygen for 90 minutes, reassess after 30 minutes:
• • If vision improves significantly at 2.0 ATA, remain at this depth for the rest of the treatment. 
  • If vision fails to improve significantly at 2.0 ATA after 30 minutes, compress to 2.4 ATA. Two 5-10 minute air breaks are required for pressures exceeding 2.0 ATA
• If 2.4 ATA compression is needed, reassess after 30 min:
• • If vision improves significantly at 2.4 ATA, conduct a U.S. Navy treatment Table 6.
  • If vision does not improve significantly at 2.4 ATA, you may consider compressing to 2.8 ATA. If no improvement occurs after the first 20-minute breathing period, consider converting to a U.S. Navy Treatment Table 6.
• If U.S. Navy Treatment Table 6 is needed, reassess after 30 min:
• • If vision improves significantly with the U.S. Navy Treatment Table 6, complete the treatment. Post-treatment,  consider inpatient monitoring and supplemental oxygen. Recovery of vision during the initial treatment of CRAO with HBOT indicates some retinal viability. 
  • If there is no response to the initial U.S. Navy Treatment Table 6, options are to give 2 additional treatments at 2.8 ATA with two ten-minute air breaks twice daily, to discontinue HBOT, or continue with normobaric oxygen.

• Immediately after completion of HBOT, monitor patient and visual status at the chamber for 2 hours
• If vision remains normal and admission to hospital is not possible, patient may be discharged home with instructions to monitor vision every hour
• If vision loss recurs, continue HBOT twice daily until the angiogram normalizes or until  visual improvement is present and does not change between treatments
• If patient is a non-responder, this should be evident in the first 2-3 treatments.
• Follow up by retina specialist

Treatment Threshold

6 – 12 treatments (Utilization/peer review recommended for patients treated for more than three days after clinical plateau and no further improvement.)

Coding

Refer to the ICD-10 Guideline for the appropriate ICD-10 code 

Comments

• If diabetes mellitus, blood glucose should be checked within an hour prior to treatment and immediately post-HBOT by unit personnel. 
• This indication is not covered by Medicare but may be covered by commercial carriers. Medicare patients must sign an Advanced Beneficiary Notice (ABN) to receive HBO treatment.