Eyes with PPG and normal control eyes meeting the eligibility criteria were enrolled from the Glaucoma Clinic of Seoul National University Hospital. If both eyes of a patient were eligible for the study, only one eye was randomly chosen for inclusion.
All patients showed a best-corrected visual acuity (BCVA) of 20/40 or better, spherical equivalent refractive error within ±5.00 diopter (D), astigmatism within ±3.00 D, an open anterior chamber angle, and good-quality red-free fundus photographs. All patients included in the study were familiar with standard automated perimetry (SAP) (Humphrey field analyzer II; Carl Zeiss Meditec) from the earlier experience of having undergone at least two VF tests. The results of the Humphrey visual field (HVF) test with the Swedish interactive threshold algorithm 30-2 standard in this study were reliable in all subjects (i.e., fixation loss < 20%, false-positive and false-negative rates < 33%). Excluded from the study were eyes with a history of amblyopia, uveitis, intraocular surgery (excepting uncomplicated cataract surgery), diabetes, ocular diseases possibly affecting the peripapillary area (e.g., large peripapillary atrophy), or macular area (e.g., epiretinal membrane), and any other ocular or systemic diseases affecting the VF (e.g., retinal vein occlusion, ischemic optic neuropathy).
Eyes with PPG were defined as eyes with normal VF results and one or more localized RNFL defects (on red-free fundus photographs) that were associated with a glaucomatous disc appearance (e.g., notching or thinning of neuroretinal rim), which have documented evidence of progression (e.g., focal or diffuse narrowing of neuroretinal rim, increased excavation, increased width or depth of RNFL defects) through stereoscopic disc photography (SDP) or red-free fundus photography performed at least 6 months before enrollment. A normal VF was defined as the pattern standard deviation (PSD) with a
P value of more than 5% and the glaucoma hemifield test result within normal limits.
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Normal control eyes were defined as eyes having an IOP ≤ 21 mm Hg with no history of increased IOP, an absence of glaucomatous disc appearance, no visible RNFL defect on red-free fundus photography, and a normal VF result in at least two VF tests. Matching for age was performed by randomly selecting one healthy control subject within 2 years of age for each subject with PPG.