Increased CCT can be related to stromal edema caused by hypoxia's effect on corneal endothelial function. Although TOS increased at high altitude, TAS did not show any parallel increase. Since this was nonacclimatized climbing, the antioxidant system could not have reached sufficient levels to counterbalance the observed oxidant stress.

Purpose To evaluate the response of the anterior segment of the eye against oxidative stress during acute exposure to high altitudes. Methods Forty volunteers were examined and measurements performed at Erciyes University Medical Faculty,Ophthalmology Clinic, Kayseri,Turkey(1080m). On the following day, participants were transported to Mt. Erciyes Ski Center by bus(2200m); thereafter they climbed to an altitude of 2800m.with a moderate pace. Central corneal thickness, intraocular pressure,spheric equivalent of refraction, arterial oxygen pressure,blood pressure, pulse rate and body temperature were measured at both altitudes. Venous blood samples were taken from volunteers at both altitudes;total oxidant status (TOS),total antioxidant status(TAS),advanced oxidation protein products (AOPP), xanthine oxidase (XO), thiol, adenosine deaminase(ADA)levels were investigated at 1080m and 2800m. Results TOS(7.02µmol H2O2 equiv/L, range:0.49‐22.07) and AOPP(220.74µmol/L,range:103.81‐667.35)significantly increased at high altitude, compared to low altitude levels (3.32µmol H2O2 equiv/L range:0.92‐18.41,and 195.58µmol/L,range:84.77‐663.16, resp; p<0.05).IOP significantly elevated at high altitude (14.45±3.54mmHg vs 13.22±2.74mmHg; p<0.05). There was a significant positive correlation between IOP and TAS levels(p<0.05).No significant correlation was found between spherical equivalent or central corneal thickness with the investigated oxidation parameters at both altitudes Conclusion We conclude that oxidative stress markers, TOS and AOPP are increased along with IOP during acute exposure to hypoxic environment at high altitudes and that antioxidant system may have a limited capacity to counter balance this effect because of acute unacclimatized ascent.