METHODS:This was a retrospective cross-sectional study. Data were collected from Tibetan patients who visited the People's Hospital of Xizang Autonomous Region from September 2019 to October 2021. Participants were divided into two groups based on their permanent residence altitude: a higher altitude group(2 500-3 750 m)and a very high-altitude group(>3 750 m). The eye with better best corrected visual acuity was selected for each participant. Intraocular pressure, refractive error, and anterior segment biometric measurements \〖white-to-white corneal diameter(WTW), central corneal thickness(CCT), anterior chamber depth(ACD), lens thickness(LT), axial length(AL)\〗 were recorded and compared between the two groups.

RESULTS: A total of 43 Tibetan patients(43 eyes)were enrolled in this study, comprising 23 males and 20 females, with a mean age of 57.88±13.90 y. There were 19 patients(19 eyes)in the very high-altitude group and 24 patients(24 eyes)in the higher altitude group. The mean intraocular pressure in the very high-altitude group was 11.79±1.72 mmHg, which was significantly lower than 13.44±2.43 mmHg in the higher altitude group(P=0.019). CCT in the very high-altitude group was 482.70±23.76 μm, significantly thinner than 503.00±31.09 μm in the higher altitude group(P=0.012). AL in the very high-altitude group was 22.96±0.96 mm, significantly shorter than 23.64±1.10 mm in the higher altitude group(P=0.020). No statistically significant differences were found between the two groups in WTW, ACD, LT, or refractive error(all P>0.05).

CONCLUSION:Among the Tibetan population in Xizang autonomous region, as the altitude of residence increases, intraocular pressure significantly decreases, CCT becomes thinner and AL shortens. These morphological changes suggest possible adaptive remodelling of the eye in very high-altitude environments, and a thinner cornea may be an important factor contributing to the lower measured intraocular pressure values.