The accommodative response profile in Chinese adolescent students
Zhi LIN OD, Shuiming Yu MSc, Xiang Chen PhD
Zhongshan Ophthalmic Center, Sun Yat-sen University, China 510060
Purpose: To investigate the profile of accommodative responses in a group of Chinese adolescent students by open-field auto-refractor.
Method: 966 high school student subjects (17.2 ± 2.1 yrs) were recruited; Shin-Nippon open-field auto-refractor was used to determine spherical equivalent refractive error under full corrected spectacle at 6 meters, 40cm, 33cm and 21 cm, respectively. The target letter size is equal to 20/30. Accommodative responses were calculated by accommodative demand minus results from the refractor. Spherical equivalence of the right eye’s refractive error was used for calculation and analysis.
Results: The subjects were divided into two groups: Emmetropia (n= 399, mean RE -0.09D ± 0.41D), Myopia (n=567, mean RE -2.84D ± 1.39 D). Accommodative responses were assessed successfully at each distance with all the subjects (N=966). The mean lag was +1.16 D (± 0.41D ) @ 40 centimeters, +1.22 D (± 0.43D ) @ 33cm, + 1.51D (± 0.48 ) @ 21 cm in myopia group. The mean lag was +0.98 D (± 0.40D ) @ 40 centimeters, +1.03 D (± 0.41D ) @ 33cm, + 1.26D ( ± 0.47 ) @ 21 cm in emmetropia group. There is a significant difference within different exam distance ( p < 0.05 ) of accommodative lag for both emmetropia and myopia group. And there is a significant difference for the lag measurements between two groups at each distance.
Conclusion: Accommodative lag are higher in myopia group comparing to the emmetropia group in these Chinese high school student population. The amount of the lag is correlated to the measuring distance, the closer the distance, the bigger of the accommodative responses. Further investigation is needed to clarify whether the lag is the cause or the result of the myopia development.