All glaucoma subjects were recruited prospectively, in a consecutive manner, from the glaucoma clinic of the Asan Medical Center, Seoul, Korea. At initial evaluation, each subject underwent a complete ophthalmic examination, including medical, ocular, and family histories; visual acuity (VA) testing; visual field perimetry (Humphrey Field Analyzer [HFA]; Swedish Interactive Threshold Algorithm (SITA) 24-2 test; Carl Zeiss Meditec, Dublin, CA); multiple intraocular pressure (IOP) measurements by Goldmann applanation tonometry (GAT); stereoscopic optic nerve head photography; and SD-OCT scanning (RTVue-100; Optovue). All patients with glaucoma had had more than one experience with visual field perimetry testing. To minimize the learning effect, only the second perimetric test was used in the analysis. For inclusion in the study, all participants had to meet the following criteria: best-corrected VA of 20/30 or better, with a spherical equivalent within ±5 D and a cylinder correction within +3 D; presence of a normal anterior chamber and open-angle on slit lamp and gonioscopic examinations; and reliable visual field test results with a false-positive error <15%, a false-negative error <15%, and fixation loss <20%. Subjects with any other ophthalmic or neurologic condition that could result in visual field defects, with a history of any intraocular surgery or with a history of diabetes mellitus, were excluded.
Glaucomatous eyes were defined as having VF defects, as confirmed by at least two reliable VF examinations and the presence of a compatible glaucomatous optic disc that showed increased cupping (a vertical cup-disc [C/D] ratio >0.6), a difference in vertical C/D ratio of >0.2 between eyes, diffuse or focal neural rim thinning, disc hemorrhage, or RNFL defects. Eyes with glaucomatous VF defects were defined as those with a cluster of three points with probabilities of <5% on the pattern deviation map in at least one hemifield, including at least one point with a probability of <1%; a cluster of two points with a probability of <1% and a glaucoma hemifield test (GHT) result outside 97% of age-specific normal limits; or a pattern standard deviation (PSD) outside 95% of normal limits. One eye was randomly selected if both eyes were found to be eligible for the study.
Mean sensitivity (MS) was evaluated by SAP (HFA; Carl Zeiss Meditec, Inc.). MS was expressed in two ways: decibel (dB) and nonlogarithmic 1/L scales (L; luminance measured in lamberts). The DLS at each tested location can be simply written as DLS (dB) = 10 × log
10 (1/L). The nonlogarithmic 1/L value at each tested location was calculated by dividing the decibel reading by 10 followed by derivation of the antilogarithm. Two test points next to the blind spot were excluded from analysis. The global MS was defined as the average value of the DLS obtained at each test point. The superior retinal MS associated with the inferior hemiretinal GCCT and pRNFLT measurements was calculated using data from 26 test points in the superior hemifield, and the inferior retinal MS referable to superior hemiretinal GCCT and pRNFLT test data was calculated from data at 26 test points in the inferior hemifield. The details of MS calculation have been described elsewhere.
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All participants gave written informed consent before enrollment. All procedures conformed to the Declaration of Helsinki, and the study was approved by the Institutional Review Board of the Asan Medical Center, University of Ulsan, Seoul, Korea.