Incidence and Progression of Myopia in Early Adulthood

Importance: Myopia incidence and progression has been described extensively in children. However, few data exist regarding myopia incidence and progression in early adulthood. Objective: To describe the 8-year incidence of myopia and change in ocular biometry in young adults and their association with the known risk factors for childhood myopia. Design, Setting, and Participants: The Raine Study is a prospective single-center cohort study. Baseline and follow-up eye assessments were conducted from January 2010 to August 2012 and from March 2018 to March 2020. The data were analyzed from June to July 2021. A total of 1328 participants attended the baseline assessment, and 813 participants attended the follow-up assessment. Refractive information from both visits was available for 701 participants. Participants with keratoconus, previous corneal surgery, or recent orthokeratology wear were excluded. Exposures: Participants' eyes were examined at ages 20 years (baseline) and 28 years. Main Outcomes and Measures: Incidence of myopia and high myopia; change in spherical equivalent (SE) and axial length (AL). Results: A total of 516 (261 male [50.6%]) and 698 (349 male [50.0%]) participants without myopia or high myopia at baseline, respectively, were included in the incidences analyses, while 691 participants (339 male [49%]) were included in the progression analysis. The 8-year myopia and high myopia incidence were 14.0% (95% CI, 11.5%-17.4%) and 0.7% (95% CI, 0.3%-1.2%), respectively. A myopic shift (of 0.50 diopters [D] or greater in at least 1 eye) occurred in 261 participants (37.8%). Statistical significance was found in longitudinal changes in SE (-0.04 D per year; P <.001), AL (0.02 mm per year; P <.001), and lens thickness (0.02 mm per year; P <.001). Incident myopia was associated with self-reported East Asian vs White race (odds ratio [OR], 6.13; 95% CI, 1.06-35.25; P =.04), female vs male sex (OR, 1.81; 95% CI, 1.02-3.22; P =.04), smaller conjunctival ultraviolet autofluorescence area (per 10-mm²decrease, indicating less sun exposure; OR, 9.86; 95% CI, 9.76-9.97; P = <.009), and parental myopia (per parent; OR, 1.57; 95% CI, 1.03-2.38; P = <.05). Rates of myopia progression and axial elongation were faster in female participants (estimate: SE, 0.02 D per year; 95 % CI, 0.01-0.02 and AL, 0.007 mm per year, 95 % CI, 0.00.-0.011; P ≤.001) and those with parental myopia (estimate per parent: SE, 0.01 D per year; 95% CI, 0.00-0.02 and AL, 95% CI, 0.002-0.008; P ≤.001). Education level was not associated with myopia incidence or progression. Conclusions and Relevance: These findings suggest myopia progression continues for more than one-third of adults during the third decade of life, albeit at lower rates than during childhood. The protective effects of time outdoors against myopia may continue into young adulthood..