HBOT Therapy for Eye Disorders
The oxygen tension in the posterior chamber is higher than in the anterior chamber. The cornea utilizes atmospheric oxygen. This oxygen can diffuse across the cornea. When breathing 96% – 97% oxygen, the tissue oxygen levels for both chambers goes up by 45%. The retinal venous hemoglobin also increases substantially when 96% – 97% oxygen is inhaled, the resulting hyperoxia (increased oxygen level). HBOT does not reduce the intra-ocular pressure, however, it may reduce the accompanying swelling and associated ischemia (lack of oxygen).
Hyperoxic myopia has been described when higher atmospheres (greater than 2.0-2.5) are used. This corrects itself in about a 1- month period. Cataract formation has been described with higher atmospheres and prolonged number of sessions. (48 sessions). The addition of high levels of antioxidants including carnosine is helpful in eliminating the free radical effect of HBOT. Retrolental fibroplasia has not been reported as a complication of HBOT in adults. Vitamin A also offers protection when hyperbaric pressures are utilized. When possible changes in the lens are suspected, initially myopia or shortsightedness may occur. Ocular HBOT is contraindicated in certain silicone orbital prostheses, in the presence of a gas bubble within the eye (not when a gas bubble occurs during HBOT usage).
Managing Eye Disorders with HBOT
- Central Retinal Artery Occulusion
Outcomes are much higher in patients with cilio-retinal arteries. management is most effective the sooner HBOT is administered after the occurrence of the event, so as to minimize the changes and extent of retinal damage. management must continue until retinal artery flow resumes. Carbogen (Carbon Dioxide) should be used with the increased oxygen to create vasodilatation to overcome the vasoconstriction that may result from the HBOT (help with natural vasodilators/blood flow enhancers such as Ginko Biloba and Hawthorn Berry may also be helpful)
Good outcomes can be achieved if HBOT is administered within 8 hours of CRO. Some increase in visual levels can be obtained, even if therapy is commenced within 24 hours.
Sclerosis is a potentially blinding occurrence when various adjuncts are administered post-surgery to prevent recurrence such as Mitomycin-Cand Beta-radiation. HBOT prevents this complication.
Anterior segment ischemia is a potential complication following surgery for strabismus. Adjunctive management with topical steroids, systemic steroids and cycloplegics (for pain due to ciliary spasm), are used with HBOT.
- Ischemic Optic Neuropathy (Naion)
This condition usually occurs in the elderly with the commonest underlying conditions being diabetes, hypertension, and nocturnal hypotension. It has also been associated with Erectile Dysfunction medications. Good results are obtained with HBOT if no significant atrophy is already present, usually when patient presents within 21 days of onset.
Arteritic optic neuropathy: This is characterized by ischemic damage to the optic nerve secondary to Giant Cell Arteritis. This should be managed with high dose steroids, and complimented with HBOT.
- Ischemic Retinal Vein Occlusion
Risk factors include Glaucoma, age, gender, Systemic Vascular Disorders, and Hyperviscosity syndromes. This condition is divided into Ischemic and Non-Ischemic RVO. The latter has a better course and outcome than the former. Tissue hypoxia is not as severe as in central retinal artery occlusion. The main thrust of management is to prevent/ reverse neovasculariztion that may result in glaucoma, pain and loss of the eye. Most of the therapy is directed at altering the blood viscosity. HBOT plays a part in reversing retinal ischemia, and macular edema (therefore, the main indicator is ischemic central retinal artery occlusion).
- Cystoid Macular Edema
This may occur post-surgically and secondary to inflammatory conditions such as HLA-B27 associated inflammation, TB and Lyme disease. The inflammatory conditions should be managed with a combination of natural supplements that depress the inflammatory cytokines plus HBOT. In the case of uveitis the patient may need repeated HBOT to retain eyesight.
- Toxic Amblyopia
This may occur secondary to quinine, methanol, lead, chloramphenicol, digoxin, and ethambutol. Improvement in vision may occur in as much as 75% of cases from HBOT.
- Toxic Pigmentosa
HBOT may improve the visual acuity and slow down progression of the disease. Since oxidative stress is a possible underlying mechanism; management should be directed at reducing this in concert with HBOT. The antioxidant administered may also help to overcome any free radical formation that occurs as a result of the HBOT.
- Diabetic Retinopathy
HBOT is likely to be of benefit early in the disease, and when acute episodes of edema occur .The more chronic the disease the poorer the outcome from HBOT.
HBOT has been helpful in the management of this condition.
- Secondary Keratoendotheliosis
This may range from mild post-operative corneal edema to bullous keratopathy, which may complicate cataract removal. HBOT may improve occurrences in most of the cases that occur. Improvement occurs as a result of reduction of edema, reducing hypoxia (ischemia).
- Complications of Sickle Cell Disease
HBOT is indicated to overcome the ischemia due to obliteration of arterioles and venules. HBOT is also of assistance when ischemia results secondarily to retinal detachment that may occur in these patients (which often results in anterior segment (or chamber) ischemia). Sickle Cell patients often need Scleral Buckling procedures for their retinal detachments. They may develop a proliferative vitreo-retinopathy that may be diminished with HBOT.
Since there may be an element of underlying ischemia of the pericapillary choroid and the optic nerve head. Although HBOT may not reduce the intraocular pressure, it may reduce the edema and ischemia. This condition may need at least a 20-management protocol, and possibly more managements, as long as visual field improvement occurs. Maintenance HBOT is also advisable. Therapy that is combined with high levels of antioxidants results in the most favorable outcomes.
- George Allibone M.D.