Prevalence of refractive errors in Mexican patients with keratoconus

Background: The purpose of this study was to determine the prevalence of refractive errors in Mexican patients with keratoconus (KCN) and to describe their clinical characteristics. Methods: In this retrospective study, we reviewed the records of Mexican patients with KCN for the year 2012. Criteria for classifying refractive errors included the following: emmetropia -0.25 to +0.25 sphere, myopia >-0.25 sphere, hyperopia >+0.25 sphere, and astigmatism >-1.00 cylinder. Patient information was collected on refraction results, refractive diagnosis, slit-lamp examination, keratometry values, contact lens features, and best visual acuity with a contact lens. The prevalence of refractive errors was estimated by dividing the total number of eyes in the study by the number of refractive errors found. Results: The study population comprised 426 patients, including 785 eyes with KCN. KCN was found more frequently in males (55.6%) than in females. The mean patient age was 28.1±10.3 years, and there was a greater frequency of moderate KCN. Compound myopic astigmatism had a prevalence of 87.3% and was present in all grades, although there are other types of refractive errors. The spherical rigid contact lens was the most frequently adapted lens (96%), and the contact lens parameters varied with disease progression. Conclusion: The most common refractive error is compound myopic astigmatism, although there are many refractive errors that have not been described to date in the KCN population. The main lens used for correction is the spherical rigid contact lens. Finally, the parameters to adjust contact lenses change according to disease progression.