Intraocular Pressure During Static Apnea

Breath-hold diving is associated with marked physiological changes, including hypoxemia, hypercapnia, bradycardia, and increases in blood pressure. The effect of prolonged breath-holding on intraocular pressure (IOP) remains insufficiently understood.

This prospective observational study investigated changes in intraocular pressure during dry static apnea (STA) in adult breath-hold divers. Participants performed breath-holds in a supine position after a standardized resting period.

Intraocular pressure was measured using a rebound tonometer (Icare Pro, Icare Finland Oy, Helsinki, Finland). Blood pressure was measured using an automated sphygmomanometer (Omron M6 Comfort, Omron Healthcare, Kyoto, Japan). Peripheral oxygen saturation and heart rate were continuously monitored using a pulse oximeter (Beurer PO 80, Beurer Healthcare, Germany).

Measurements were obtained at baseline, during apnea and after resumption of breathing.

The primary objective was to quantify changes in intraocular pressure during STA. Secondary objectives included assessment of physiological responses and analysis of their relationship with IOP changes.

Inclusion criteria

• age over 18 years
• breath-hold divers at the amateur or professional level
• signed informed consent

Exclusion criteria

• known intraocular hypertension or glaucoma
• refractive error > ±5.00 D
• history of an eye injury
• previous surgery for cataract, strabismus, or pars plana vitrectomy
• corneal disease
• acute eye infection