Detailed Ophthalmic Examination Protocol

The ophthalmic examination has been described in detail by Höhn et al. [21 (link)]. Refraction and distance-corrected visual acuity were measured using a Humphrey Automated Refractor/Keratometer (HARK) 599 (Carl Zeiss AG, Jena, Germany) in both eyes, beginning with the right eye. Best-corrected visual acuity was measured using built-in Snellen charts ranging from 20/400 to 40/20 (decimal 0.05 to 2.0). Below that visual acuity, we used a visual acuity chart at a distance of one meter up to 20/800, and then counting fingers, hand movements, and testing of light perception. The spherical equivalent was calculated as the spherical correction value plus half the cylindrical power. Intraocular pressure was measured with an air-puff noncontact tonometer (Nidek NT-2000; Nidek, Co., Gamagori, Japan), again beginning with the right eye. The mean of three measurements within a 3-mmHg range was obtained for each eye. History of eye disease was assessed in a short interview preceding the eye examination.