Prevalence of refractive conditions in the general population attending eye care clinics in the north of Portugal

Abstract

The purpose of this study was to report the fi rst estimations on the prevalence of refractive conditions in a Portuguese population attending several ophthalmologic and optometric clinics within the same region. Methods: Values of non-cycloplegic subjective refraction from the right eye of 4288 patients (40.08±18.75 years) were analyzed to estimate the prevalence of refractive conditions as a function of age and gender. The prevalence of anisometropia and presbyopic correction as a function of age and gender were also investigated. Results: Mean spherical equivalent refractive error was –0.29±2.01D. 29.8% of the patients had myopia, 45% had emmetropia and 25.2% had hyperopia. Young adults ranging from 20 to 35 years of age presented the highest prevalence of myopia. Conversely, the peak of hyperopic condition was for the oldest population. Anisometropia, defi ned as a difference in spherical equivalent equal or higher than 3D was present in 1.4% of our population. Conclusion: The prevalence of refractive conditions has been established for a large non-randomized sample of the Portuguese population for the fi rst time. Important refractive changes were evidenced in the fi fth decade of life, comprising an increase in the prevalence of hyperopia along with a shift in the amount of astigmatism. Although this study is not representative of the overall Portuguese population, there seem to be evidence that myopia could be increasing among the younger age groups.