Taller people are more likely to have eyes with biometric parameters associated with myopia, according to a new study in Clinical and Experimental Optometry. Young adults subjects between 1.75 m and 1.95 m tended to have longer eyes, deeper anterior chambers, flatter corneas, higher axial length-corneal radius ratio and more negative refraction than other subjects. It also found that young people with a higher body mass index (BMI) are more hyperopic.
The research, based on the Anyang University Students Eye Study (AUSES), in Anyang, Henan Province, in central China, broke the subjects down into five quintiles by height. The first quintile were between 1.40 m and 1.59 m tall, the second were between 1.60 m and 1.63 m, the third were 1.64 m and 1.68 m, the fourth were between 1.69 m and 1.74 m and the fifth were 1.75 m and 1.95 m.
A total of 5657 students were included in the study. From September 2016 to June 2017, their cycloplegic refraction and corneal curvature radius (CR) were measured using an autorefractor, and their ocular parameters were recorded. Each participant’s height, weight and BMI was recorded during their annual, standardized physical examinations.
Subjects in the fifth quintile, the tallest individuals, had mean axials lengths of 25.24 (± 1.21) mm. These were significantly longer than the first quintile’s axial lengths of 24.38 (± 1.15) mm. The fifth quintile’s anterior chamber depths were 3.29 (± 0.24) mm while the first quintile’s were 3.17 (± 0.25) mm. These biometric measurements are associated with greater rates of myopia, the researchers said, suggesting that height could be a predictor of myopia. The fifth quintile also had the highest mean CR at 7.85 (± 0.25) mm, compared with the first quintile’s 7.62 (± 0.24) mm.
The research also shows the taller subjects with a higher BMI had longer axial lengths, deeper anterior chambers and flatter corneas than shorter subjects with lower BMIs.
After adjusting for age, gender, weight, parental myopia and time outdoors and spent on near work, each centimeter of height increase was linked with more negative refraction as – 0.023 D, a 0.032 mm increase in axial lengths, a 0.003 mm increase in anterior chamber depths, a 0.008 mm increase in CR.
Also, a one kilogram heavier person was more likely to have less negative refraction as 0.011 D, a 0.001 mm deeper ACD and a 0.002 mm flatter cornea.
Although several population-based and school-based studies have looked at links between body stature, refraction and biometry parameters, most of them have primarily included children or adults over 40. This study focused on subjects between 16 to 26 years old.
Researchers suggest that the differences in stature may partially explain the variation in refraction and ocular biometry.
Wei S, Sun Y, Li S, et al. Effect of body stature on refraction and ocular biometry in Chinese young adults: The Anyang University Students Eye Study. Clin Exp Optom. Published online August 31, 2020. doi: 10.1111/cxo.13137