Visual impairment in highly myopic eyes: the ZOC-BHVI high myopia cohort study

Importance: Understanding visual impairment (VI) under different definitions and potential risk factors in high myopic is important for future myopia control. Background: Limited studies exists investigating the VI among high myopic and with varying VI definitions. Design: Registry cohort study. Participants: Eight hundred and eighty-four participants were from ZOC-BHVI study. Methods: Subjects aged 7 to 70 years with high myopia were enrolled. Uncorrected visual acuity and best-corrected visual acuity (UCVA and BCVA), cycloplegic refraction, axial length (AL), corneal curvatures, anterior chamber depth and lens thickness were measured. Axial length/corneal radius of curvature ratio (AL/CR ratio) was calculated. Fundus lesions were graded into five categories. VI and blindness were defined based on the better-seeing eye according to the World Health Organization (WHO) criteria and US criteria. Multiple logistic regression analysis was used to assess risk factors for VI. Main Outcome Measures: Rates of VI and blindness. Results: A total of 884 participants were included, with mean (SD) age 18.5 (12.4) years and 46.4% male. Rate of UCVI/blindness were 72.6%/27.3% and 17.9%/82.1% based on WHO and US criteria. With respect to BCVA, 4.1%/5.9% of participants had BCVI using two definitions, whereas the rate for blindness was 0.2% and 0.6%. After adjusting confounders, multiple logistic regression showed that more severe fundus lesions, greater AL/CR ratio were at a higher risk of being VI, both in two definitions (P <.005). Conclusions and Relevance: The rate of VI and blindness in highly myopic patients varies significantly using different definition. Severe fundus lesions and greater AL/CR ratios were associated with a higher risk of VI.