Our study was a clinic-based, cross-sectional study of 388 Korean men and women, aged 30 to 89 years. The subjects who were enrolled either attended a general ophthalmology clinic for routine eye examinations or minor external ocular discomforts, such as dryness or blepharoconjunctivitis, or were volunteers, or employees or families of employees of the Asan Medical Center, Seoul, Korea. They were recruited consecutively from March to October 2009. All participants underwent a comprehensive eye examination. This included best corrected visual acuity (BCVA) measurements using the logarithm of minimum angle of resolution (logMAR chart, The Lighthouse, Long Island, NY), slit-lamp (model BQ 900, Haag-Streit, Bern, Switzerland) examination of the anterior segment, and intraocular pressure (IOP) measurement by Goldmann applanation tonometry, as well as stereoscopic optic disc examination with a 90 diopter lens (Volk Optical Inc., Mentor, OH) through an undilated pupil, gonioscopy, ultrasound pachymetry, keratometry, A scan biometry (IOL Master, Carl Zeiss Meditec Inc., Dublin, CA), and AS-OCT (Visante, version 2.0).
For inclusion, all enrolled subjects met the following criteria: BCVA of 20/30 or better, open angle by gonioscopy, no existing pathology by slit-lamp, no significant media opacity that obscured fundus examination, and no retinal pathology. Exclusion criteria were a history of any intraocular surgery, including laser treatment, as well as the use of topical drugs affecting pupil diameter, and history of ocular disease or trauma. If both eyes qualified for the study, one eye was chosen at random. More details have been reported previously.
3 Our study was approved by the Institutional Review Board of the Asan Medical Center (Seoul, Korea), and followed the tenets of the Declaration of Helsinki.