To determine 4-year changes of corneal biomechanical parameters in Iranian children aged 7-11 years and their determinants.

In this 4-year Prospective cohort study, 468 children aged 7-11 years that were initially evaluated in 2012 were re-evaluated in 2016-2017. Multi-stage stratified cluster sampling was applied. Cycloplegic refraction (Topcon Corporation, Tokyo, Japan), biometry using LENSTAR/Biograph (WaveLight Ag, Erlangen, Germany), and corneal biomechanical assessment using Ocular Response Analyzer (Reichert Ophthalmic Instruments, Buffalo, New York, USA) were done for each subject.

All biomechanical parameters except a index decreased in the second phase. The mean changes of CH (corneal hysteresis) and CRF (corneal resistance factor) was 0.68±0.16 mmHg (for both parameters) during four years. The mean difference in CH and CRF was 0.23±0.23 and 0.24±0.23 mmHg in girls and 1.03±0.23 and 0.96±0.23 mmHg in boys, respectively. Different age groups showed varying amounts of decrease in all parameters except for a index. The age group 10 years experienced the smallest change in CH (0.02±0.48 mmHg) and CRF (0.20±0.47 mmHg) and the age group 11 years showed the greatest disparity in CH (1.41±0.35 mmHg) and CRF (0.99±0.34 mmHg). According to linear regression analysis, CH and CRF had a significant direct relationship with corneal power and an inverse relationship with axial length. (P<0.001)

Age and sex are determinants of classic ORA parameters. A decreasing trend was noted in the biomechanical parameters in different age groups. Moreover, the decreasing changes in the biomechanical parameters were more noticeable in boys than girls.