Prevalence and distribution of low and high myopia in Mexican outpatients: a nationwide cross-sectional clinic-based study.

Background: Myopia is a global public health concern and a leading cause of distance vision impairment, affecting mainly children and young adults. Although several studies have reported myopia prevalence in Mexico, recent nationwide data, especially regarding high myopia, are lacking following the COVID-19 pandemic. We estimated the prevalence and distribution of low and high myopia in a cohort of Mexican outpatients. Methods: A retrospective, cross-sectional, clinic-based study was conducted using anonymized electronic health records from Salud Digna clinics. Data included individuals aged 6-100 years undergoing routine non-cycloplegic eye examinations between January and December 2023. Myopia was defined as spherical equivalent refraction (SER) ≤ -0.50 diopters (D) in the right eye and subclassified into low (-6.0 D < SER ≤ -0.50 D) or high (SER ≤ -6.0 D). Age-standardized prevalence rates were estimated overall and by sex and geographic location. Multinomial logistic regression evaluated potential risk between demographic/clinical background and myopia severity. Results: From 3,507,826 records, 1,337,526 (38.13%) individuals were myopic (median age: 28 years; 61.4% females). Age-standardized rates for total, low, and high myopia were 44.44% (95% CI, 44.36-44.52%), 43.31% (95% CI, 43.24-43.39%), and 1.12% (95% CI, 1.11-1.14%), respectively. Low myopia was more prevalent in males, whereas high myopia predominated in females (both Conclusion: Astigmatism was a risk factor for myopia, with increasing severity raising the risk of developing both forms of myopia. Although high myopia remains relatively uncommon nationally, its increasing prevalence from childhood to early adulthood highlights the need for early detection and close monitoring to mitigate future visual impairment in Mexico.