The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia

Inclusion Criteria: * Age range 18-30 years old * Visual acuity of 20/20 or better Exclusion Criteria: * Refractive error \>±6.00 DS and/or ± 2.00 DC * History or presence of ocular disease * Family history of diabetes or glaucoma * History of intraocular or refractive surgery * Nursing or pregnant women * History of clinically diagnosed endocrine disease * History of vascular disease, cardiovascular disease, or any treated respiratory disorders (seasonal asthma excluded from this so long as subject not taking Rx at the time) * History of systemic hypertension * Habitual smoking * Use of medications that affect blood flow