Our retrospective observational study protocol was approved by the Institutional Review Board of the Catholic University of Korea, Seoul, Korea. The study design followed the tenets of the Declaration of Helsinki for biomedical research. Eyes with NTG and meeting the eligibility criteria were enrolled consecutively from a database of patients who were examined for glaucoma between March 1, 2009 and December 31, 2009 in the Department of Ophthalmology, Seoul St. Mary's Hospital.
Inclusion criteria for all patients were best-corrected visual acuity of 20/40 or better, refractive error of greater than −6 spherical diopters (D) and 2 D cylinder, and transparent ocular medium (nuclear color or opalescence, cortical or posterior subcapsular lens opacity <1) according to the Lens Opacities Classification System III.
15 The inclusion criteria for early NTG were eyes with a normal open angle on gonioscopy, initial untreated intraocular pressure (IOP) of <21 mm Hg, and the presence of a glaucomatous optic neuropathy (diffuse or focal rim thinning, cupping, notching, hemorrhage, RNFL defect) with a corresponding reproducibly reliable visual field defect coincident with our criteria for PFS or PNS. Subjects with a history of previous intraocular surgery, diseases that may affect the peripapillary area, or systemic disease or medication that may affect visual acuity were excluded.
Each patient had undergone comprehensive ophthalmic examinations, including a best corrected visual acuity test, slit-lamp biomicroscopy, IOP measurement by Goldmann applanation tonometry, gonioscopy, central corneal thickness (CCT) measurements using ultrasonic pachymetry (SP-3000; Tomey Corp., Nagoya, Japan), and dilated funduscopic examination. Stereoscopic optic disc photography and monoscopic red-free digital fundus photography (Canon Cf-60 UW with Canon EOS D-6 CCD camera; Canon, Tokyo, Japan) were performed. Patients were re-examined usually at 6- to 12-month intervals; the same tests were performed with the exception of CCT measurements. Data regarding age at the time of study entry, visual acuity, maximum known untreated IOP from records, spherical equivalent, and disc hemorrhage detection during follow-up were collected.