Prevalence and Risk Factors of Myopia in Young Adults: Review of Findings From the Raine Study

Abstract

Myopia tends to develop and progress fastest during childhood, and the age of stabilization has been reported to be 15-16 years old. Thus, most studies on myopia have centered on children. Data on the refractive error profile in young adulthood - a time in life when myopia is thought to have stabilized and refractive error is unaffected by age-related pathology such as cataract - are limited. The Raine Study has been following a community-based cohort of young adults representative of the general Western Australia population since their prenatal periods in 1989-1991, with eye examinations performed when participants were 20 and 28 years old. At 20 years old, prevalence of myopia in the cohort was 25.8%. Using long-term trajectory of serum vitamin D levels and conjunctival ultraviolet autofluorescence (CUVAF) area to objectively quantify sun exposure, the Raine Study confirmed a negative relationship between time spent outdoors and myopia prevalence. However, prospective studies are required to determine the amount of CUVAF area or serum vitamin D levels associated with time duration. Combining data from the Raine Study and several other cohorts, Mendelian randomization studies have confirmed a link between myopia and a genetic predisposition toward higher education. Several novel potential associations of myopia or ocular biometry were investigated, including fetal growth trajectory, which was found to be significantly associated with corneal curvature at 20 years. By age 28, myopia prevalence had increased to 33.2%. Between 20 and 28 years old, myopia progressed and axial length elongated, on average, by -0.041D/year and 0.02 mm/year, respectively. Smaller CUVAF area at follow-up, female sex, and parental myopia were significant risk factors for myopia incidence and progression between 20 and 28 years. Given the limited research in young adults, further investigations are warranted to confirm the Raine Study findings, as well as identify novel genetic or environmental factors of myopia incidence and progression in this age group.

Keywords: axial length; education; myopia; risk factors; sun exposure; the Raine Study; time spent outdoors; young adults.

Figure 1

Refraction of a participant with rapid myopia progression from 20 (year 2010) to 28 years old (year 2018). Refraction (spherical equivalent) history obtained from participant's optometrist *apart from 2013 when the participant did not visit the optometrist. The participant reported their occupation during the 8-year period to be computer-intensive (at or close to 100%), with the exception of the year 2013 and mid-2016 to 2017, when most of their time was spent on outdoor academic field work or traveling. While no refraction data was available at 2013 (*), from 2016 to 2017, no myopia progression was documented.