Measurement and analysis of corneal biological parameters from Tibetan junior middle school students in high altitude area

Objective

To measure and analyze the corneal biological parameters of Tibetan junior middle school students who have lived in Mozhugongka County of Lhasa city for a long time.

Methods

A cross-sectional study was performed.The basic information including gender, age and grade of 1 784 Tibetan junior high school students who have lived in Mozhugongka County of Lhasa city for a long time was collected, and the corneal biological parameters were measured in May, 2020.The available data of 690 students were obtained in this study.Unilateral eye of each subject was randomly selected for statistical analysis using computer random number method.Three hundred and forty-five right eyes and 345 left eyes from 366 males and 324 females were included.There were 461 eyes from students aged 12 to 15 years, and 229 eyes from students aged 16 to 20 years.Sirius 3D corneal topography and anterior segment analysis system were used to measure the thinnest corneal thickness (TCT), central corneal thickness (CCT), anterior chamber depth (ACD), iridocorneal corneal angle, simulated K1 and simulated K2, thinnest point position.Histogram and Q-Q chart were used to assess the distribution of continuous variables except the thinnest point position of cornea.The differences in biological parameters were compared between males and females, 12-15 years group and 16-20 years group as well as right eyes and left eyes.The literature of corneal biological parameters from other ethnic group was reviewed and compared with the Tibetan subjects.This study complied with the Declaration of Helsinki and was approved by an Ethics Committee of Tibet Hospital (No.QZYY2019-IRBPJ-21).

Results

The ACD of the right eye of the students was (3.31±0.27)mm, which was significantly greater than (3.26±0.26)mm of the left eye (t=0.745, P=0.012). Mean TCT, CCT, iridocorneal angle, simulated K1 and simulated K2 were (504.99±30.73)μm, (509.10±35.82)μm, (47.45±5.70)°, (43.15±1.89)D, and (44.16±2.29)D of the right eye, and thoes of the left eyes were (503.34±29.22)μm, (508.36±28.75)μm, (47.86±5.88)°, (43.06±1.40)D and (44.16±1.53)D, respectively, with no significant differences between the right and left eyes (all at P>0.05). The ACD and iridocorneal angle were significantly greater, and the simulated K1 and simulated K2 were significantly smaller in males compared with females (all at P<0.05). There were no significant differences in TCT and CCT between males and females (both at P>0.05). The corneal biological parameters were not signficantly different between different age groups (all at P>0.05). The thinnest point of cornea distributed mainly at inferior temporal quadrant zone for the right eyes, and superior temporal quadrant zone for the left eyes.

Conclusions

Corneal biological parameters of Tibetan junior high school students in high altitude areas might be different from those of other ethnic students.Ophthalmologists should pay attention to this population in diagnosis and treatment of corneal diseases and refractive error.