All study subjects were recruited prospectively, in a consecutive manner, from our glaucoma clinic and were examined between March 2008 and December 2008 at the Asan Medical Center, Seoul, Korea. At initial evaluation, all subjects underwent a complete ophthalmologic examination including medical, ocular, and family history; visual acuity testing; the Humphrey field analyzer (HFA) Swedish Interactive Threshold Algorithm 24-2 test (Carl Zeiss Meditec, Inc); multiple intraocular pressure (IOP) measurements using Goldmann applanation tonometry; stereoscopic optic nerve photography; and Stratus OCT and Cirrus HD-OCT. All patients with glaucoma had extensive experience with HFA testing. To minimize the learning effect, only the last 2 HFA test results were used for analysis. For inclusion in the study, all participants had to meet the following criteria: best-corrected visual acuity of 20/30 or better, with a spherical equivalent within ±5 diopters and a cylinder correction within +3 diopters; presence of a normal anterior chamber and open angle on slitlamp and gonioscopic examinations; and reliable HFA test results with a false-positive error less than 15%, a false-negative error less than 15%, and a fixation loss less than 20%. Subjects with any other ophthalmic disease that could result in HFA defects or with histories of diabetes mellitus were excluded. One eye was randomly selected if both eyes were found to be eligible. Age-matched, healthy eyes formed the control group. The control group consisted of staff, their family, spouses of patients, and volunteers from the eye clinic and hospital. The control group had no history of ocular symptoms or disease and no intraocular incisional or laser surgery. These control eyes had an IOP lower than 22 mm Hg, with no history of IOP elevation, and were normal by VF examination. Glaucomatous eyes were defined as those with glaucomatous VF defects confirmed by at least 2 reliable VF examination results and by the presence of a glaucomatous optic disc that showed increased cupping (vertical cup-disc ratio of >0.6), a difference in vertical cup-disc ratio of more than 0.2 between eyes, diffuse or focal neural rim thinning, hemorrhage, and nerve fiber layer defects. Eyes with glaucomatous VF defects were defined as those with a cluster of 3 points with probabilities of less than 5% on the pattern deviation map in at least 1 hemifield, including at least 1 point with a probability of less than 1%, or a cluster of 2 points with a probability of less than 1% and a glaucoma hemifield test result outside 99% of age-specific normal limits or a pattern standard deviation outside 95% of normal limits.