Axial length and its relationship to refractive error in Chinese university students

Purpose: To investigate the relationship between axial length (AL) and refractive error (RE). Methods: Participants comprised Chinese university students. In total, 894 eyes with low hyperopia to emmetropia (-0.50D < spherical equivalent (SE) < +2.00D), and 1007 eyes with moderate to high myopia (-11.00D < SE <-4.00D) were analyzed. Cycloplegic RE and AL were measured with an autorefractor and IOL Master respectively. The association between AL and RE was evaluated by linear regression. Furthermore, differences in the mean AL, as well as the correlation between AL and ocular refraction, were evaluated according to SE, sex, and age. Results: In both the moderate to high myopia and low hyperopia to emmetropia groups, mean AL was significantly longer in men (26.48 mm, confidence interval (CI) 26.41-26.56 mm; 23.82 mm, CI: 23.76-23.88 mm, respectively) than in women (25.78 mm, CI: 25.71-25.86 mm; 23.25 mm, CI: 23.17-23.33 mm, respectively). For both men and women, mean AL significantly differed among four SE groups (+0.50D < SE < +2.00D,-0.50D < SE < +0.50D,-4.00D < SE <-6.00D, SE <-6.00D, P < 0.001). The correlation coefficient between AL and ocular refraction was-0.318 and-0.277 in male and female participants, respectively, with low hyperopia to emmetropia (-0.50D < SE < +2.00D), and-0.545 and-0.437 in male and female participants, respectively, with moderate to high myopia (-11.00D < SE <-4.00D). There were no age-related effects on SE (P = 0.714) or AL (P = 0.952). Conclusions: Ocular refraction is negatively correlated with AL in Chinese university students. The correlation coefficient is greater in those with moderate to high myopia than in those with low hyperopia to emmetropia. Furthermore, the AL is longer in men than in women.