Objective Refraction and Visual Acuity

Objective refraction and distance-corrected visual acuity were measured in both eyes using a Humphrey Automated Refractor/Keratometer (HARK) 599 (Carl Zeiss AG, Jena, Germany) without cycloplegia, starting with the right eye [10 (link)]. Distance-corrected visual acuity was measured using the built-in Snellen charts, ranging from 20/400 to 40/20 (logMAR 1.3 to − 0.3). Below that visual acuity, we used a visual acuity chart at a distance of one meter up to 20/800 (logMAR 1.6), followed by counting fingers, hand movements, and the light perception test. The spherical equivalent was calculated as the spherical correction value plus half of the cylindrical power. A history of eye disease was assessed in a short interview preceding the eye examination.