Clinical relevance: Myopia is a leading cause of visual impairment worldwide, and myopia progression in young adulthood may worsen this public health issue.
Background: The aim was to describe the changes in myopia and various ocular biometry parameters, and to determine the incidence and related factors of myopic shift among young adults in China.
Methods: This 2-year prospective cohort study was conducted at the Zhongshan Ophthalmic Center, Sun Yet-san University, China. A total of 291 Chinese medical freshmen (314 enrolled at baseline) were followed over 2 years. The participants underwent detailed eye examinations at baseline and follow-up visits, including cycloplegic refraction, ocular biometry measurements, and swept-source optical coherence tomography. Visual fatigue was assessed with the Convergence Insufficiency Symptom Survey (CISS) using Rasch analysis. Questionnaire on eye care habits and physical activities was administered.
Results: A total of 291 study participants (baseline mean [SD] age, 18.7 [0.9] years; 132 [45.4%] male) were analysed. Seventy eight (26.8%) developed a myopic shift (defined as negative change in spherical equivalent worse than or equal to -0.50 D) over a 2-year period. The magnitude of subfoveal choroidal thinning was greater in participants with myopic shift, compared to those without. Axial length increased significantly by 0.12 mm in the group with myopic shift, compared to 0.02 mm in those without the myopic shift (p < 0.001) over 2 years. After multivariable adjustment, visual fatigue (using CISS) was found to be associated with the myopic shift (p = 0.02).
Conclusions: Approximately one in four Chinese medical students had a clinically significant myopic shift. Choroidal thinning and axial elongation were observed in young adults with myopic shift. Greater visual fatigue score at baseline was associated with myopic shift after multivariable adjustment.
Keywords: Adults; Myopic shift; myopia.