Participants were from a tertiary glaucoma clinic at Legacy Devers Eye Institute in Portland, OR. Inclusion criteria were a diagnosis of open-angle glaucoma, and at least six test locations that were outside age-matched normal limits on both of their two most recent visual fields (tested using the Humphrey Field Analyzer [HFA; Carl Zeiss Meditec, Inc., Dublin, CA, USA] and the SITA standard testing algorithm7). Additionally, participants were required to have a non–end-stage localized glaucomatous defect, which we defined as having at least two adjacent locations in the same hemifield (not including the blind spot) whose sensitivities differed by ≥6 dB on both of their most recent two visits. Exclusion criteria were an inability to perform reliable visual field testing, best-corrected visual acuity worse than 20/30 due to nonglaucomatous causes, history of angle closure, or any nonglaucomatous ocular pathology likely to affect the visual field. If both eyes met the inclusion and exclusion criteria, one was chosen at random for testing. All protocols were approved and monitored by the Legacy Health Institutional Review Board, and adhered to the Health Insurance Portability and Accountability Act of 1996 and the tenets of the Declaration of Helsinki. All participants provided written informed consent once all of the risks and benefits of participation were explained to them.
Participants underwent two visits, either on the same day (with a lunch break of more than an hour between so as to reduce fatigue) or on different days as close together as possible. On each visit, they underwent visual field testing using three different test algorithms, in random order; the two algorithms that are relevant to this study are outlined below. Testing was conducted using an Octopus 900 perimeter (Haag-Streit AG, Bern, Switzerland), controlled externally using the Open Perimetry Interface.
8 Although the decibel scales, which are defined relative to the maximal intensity stimulus of the instrument, differ between perimeters, in this study we report all measures using the HFA decibel scale. Software to run the testing, together with all analyses, were written using the R statistical programming language.
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