Incidence of myopic shift and related factors in young Chinese adults.

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.

Choroidal Thickness and Associated Factors among Adult Myopia: A Baseline Report from a Medical University Student Cohort.

Purpose: To report baseline information for a medical university cohort with the aim of exploring related factors for adult myopic progression. Methods: This study included Chinese freshmen students from a medical school in Guangzhou, China. All participants underwent detailed eye examinations, including cycloplegic refraction, ocular biometry and swept source optical coherence tomography. Choroidal thickness (CT) measurements were performed at nine locations in the macular area. Eye care habits and physical activities were measured by questionnaire. Results: The mean age of the study population (N = 307) was 18.8 ± 2.3 years, and 46.3% were male. The prevalence of myopia and high myopia was 92.8% and 21.1%, respectively. In emmetropia (spherical equivalent, SE -0.49D to +0.5D), mild to moderate myopia (SE -0.50D to -5.99D) and high myopia groups (SE <-6.00D), the average subfoveal CT was 300.3 ± 62.1 µm, 219.3 ± 65.4 µm and 194.0 ± 59.7 µm, respectively. In all eyes, the temporal CT was the thickest among all of the locations in the macular area, and the CT was thinnest nasally. Gender, axial length (AL), anterior chamber depth (ACD) and intraocular pressure (IOP) were the strongest related factors for subfoveal CT in mild to moderate myopia, while AL was the only significant determinant for subfoveal CT in highly myopic eyes. Conclusions: The prevalence of myopia was high in Chinese medical students. Macular CT was generally thinner in highly myopic eyes. Our study provided baseline information for the medical school cohort, including CT, AL, ACD, IOP and eye care habits.