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 884 participants from ZOC‐BHVI Study. Methods Subjects aged 7‐70 years with high myopia were enrolled. Uncorrected and best‐corrected visual acuity (UCVA & 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 5 categories. VI and blindness were defined based on the better‐seeing eye according to the World Health Organization (WHO) criteria and United States (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, while 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 < 0.005). 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.