A nationwide estimate of the prevalence of refractive errors and visual impairment among individuals presenting to optometry clinics shows the most common errors, their relative distributions, and associations with vision impairment, according to research, using Irish electronic medical records, published in the Journal of Optometry. While the study strictly includes individuals from Ireland, it may serve as a useful epidemiological resource in clinical practices that manage refractive errors, according to the report.
The retrospective analysis included 153,598 individuals (mean age, 47.94 years; 57.8% women) from 40 practices who presented between January 2015 and December 2019. Refractive error and vision impairment prevalence was obtained through electronic medical records (EMR), and investigators stratified study participants into age groups consisting of 10-year intervals.
“Our findings show that the most common refractive error in the overall clinical population was hyperopia, followed by astigmatism and myopia. The relative distributions, however, were highly age dependent and the census-based gender and age-adjustment revealed a higher proportion of myopia overall” the researchers explain. “High myopes were most likely to be vision impaired, followed by hyperopes, while the mean age of those affected by vision impairment was ten years younger in myopes compared to hyperopes.”
Hyperopia affected 40.13% of participants. A total of 27.13% of individuals had emmetropia and 32.75% had myopia — 2.38% of which had high myopia (≤-6.00 diopters [D]).
The youngest and oldest participants were most likely to have hyperopia. Children (age range, 0-9) were most likely to be hyperopic (57.38%), but it was the most prevalent refractive state for individuals aged 50 years and older. Individuals aged 20 to 29 years were most likely to have myopia (57.67%) and 3.78% of participants in this age group had high myopia. High myopia was most commonly observed in individuals aged 30 to 39 years (4.91%).
Astigmatism was present in 38.30% of study participants and slightly more common among men and boys compared with women and girls (39.07% vs 37.47%; P <.001). Individuals with oblique, against the rule, and with the rule astigmatism comprised 32.82%, 39.22%, and 27.96% of this subset, respectively.
Anisometropia was present among 13.42% of participants and varied as a function of age — affecting a higher proportion of younger children compared with older children and young adults. Minimal differences were observed across older age groups until age 60 years, where it steadily increased and peaked at 25.52% in individuals older than 80 years.
A clinically insignificant, but statistically significant, difference in visual acuity was noted between men and boys compared with women and girls, with the latter having worse visual acuity (0.025 vs 0.028 logarithm of the minimum angle of resolution [logMAR]). Visual impairment (VI) was present in 2.40% of participants with 1.99% having mild VI, 0.39% with moderate VI, and 0.01% showing blindness.
“EMR data is a useful resource and may be reasonably representative in older age groups in which ocular disease and vision impairment associated with refractive error is most likely to become manifest,” according to the study authors. “Critically, the most important contribution of this study is to provide a comprehensive baseline assessment of the distribution of refractive error and associated factors in the clinic-going population.”
Study limitations include a clinic-based, as opposed to a population-based, design and inability to access demographic factors such as ethnicity or region of residency.
Longwill S, Moore M, Flitcroft DI, Loughman J. Using electronic medical record data to establish and monitor the distribution of refractive errors. J Optom. Published online October 8, 2022. doi:10.1016/j.optom.2022.09.001