Changes to visual acuity (clearness of vision) after Hyperbaric Oxygen Therapy

INTERVENTION: Patients are administered a minimum of 20 sessions of hyperbaric oxygen therapy (HBOT) in a multiplace chamber. Each session involves the delivery of 100% oxygen at 2.4ATA, for 90 minutes. Sessions will be administered once everyday consecutively (Mon‐Fri), for a minimum of 20 sessions, up to 40 sessions (i.e. 20‐40 working days) Patients in the intervention group will receive oxygen via a plastic hood that encloses the head. This creates a seal for oxygen to accumulate, allowing patients to breathe in 100% oxygen. CONDITION: HBOT induced myopia PRIMARY OUTCOME: Best corrected visual acuity is assessed in patients of both arms, using the Snellen chart. Patients are required to don their prescription eyewear when being assessed. Ocular refraction (subjective refraction) will be assessed in patients of both arms by a qualified orthoptist assisting in the study Ocular refractive change (autorefraction) will be assessed in patients of both arms using an autorefractor SECONDARY OUTCOME: Corneal curvature will be assessed using a keratometer. INCLUSION CRITERIA: HBOT indication of at least 20 sessions Minimal visual acuity of 6/12 or better Ability to receive HBOT via mask or hood