Spatial Characteristics of Visual Field Progression Determined by Monte Carlo Simulation: Diagnostic Innovations in Glaucoma Study

Abstract

To determine the spatial characteristics of glaucomatous visual field progression in persons with glaucomatous-appearing optic neuropathy (GON) from the Diagnostic Innovations in Glaucoma Study (DIGS). Changes in pattern deviation (PD) plot values from the average of two baseline examinations to two follow-up examinations were evaluated in test locations. All were eligible, full threshold, pattern 24-2, standard automated perimetry (SAP) examinations (Humphrey Field Analyzer II; Carl Zeiss Meditec, Inc., Dublin, CA) in visual field series from 200 patients with GON confirmed on two occasions by stereophoto review. The proportion of patients exhibiting PD plot progression was determined at each of 52 locations for patients with a baseline abnormal result (P < 5% or worse) in one or more of 52 PD locations in either the first or second baseline test for a total of 2704 location pairings for each possible level of negative PD change from -1 to -50 dB. Progression was defined as any worsening of PD plot value in the follow-up test relative to the average PD plot value in the baseline tests. Monte Carlo simulation was used to determine the significance of the observed patterns of PD plot progression. Changes in PDs were dependent on their location relative to abnormal PD locations in the first test. Of those patients with an abnormality at a location at baseline (mean, 0.23 +/- 0.07), the proportion of patients changing by -2 dB or more ranged between 0.09 and 0.55 (mean, 0.29 +/- 0.06) across locations. For changes of -6 dB or more, the proportions ranged between 0.00 and 0.26 (mean, 0.08 +/- 0.04) of patients. These proportions and the proportional probabilities for each of 2704 location pairings are reported for selected levels of change. The proportional probabilities are consistent with a map of the retinal nerve fiber layer bundles. Visual field progression occurs in retinotopically constrained patterns consistent with changes along the nerve fiber bundle.