Presented in part at the Australian Glaucoma Club meeting, Sydney, Australia, February 1999, and at the annual meeting of the Association for Research in Vision and Ophthalmology, Fort Lauderdale, Florida, May 1999.
Received 4 June 1999; accepted 8 June 2000.
Abstract
Purpose
Objective perimetry in glaucoma is described using the multifocal pattern visually evoked potential (VEP). A multichannel recording technique was used to improve signal detection in healthy volunteers and assess its ability to detect glaucoma and early changes in patients with suspected glaucoma.
Design
Prospective, case-control study.
Participants
Thirty healthy volunteers, 30 patients with suspected glaucoma, and 30 patients with glaucomatous visual field defects were tested.
Method
The VEP was recorded using cortically scaled, multifocal, pseudorandomly alternated pattern stimuli with the VERIS system (Electro-Diagnostic Imaging, Inc., San Francisco, CA). An array of four bipolar occipital electrodes provided four differently oriented channels for simultaneous recording. Signals were compared for different locations within the field up to 26° of eccentricity. Healthy volunteers, patients with suspected glaucoma, and glaucoma patients with established visual field defects were tested, and results were compared with Humphrey visual fields (Humphrey Systems, Dublin, CA) performed on the same day. For reproducibility, five healthy volunteers were each tested on four separate days. The patients with suspected glaucoma and the established glaucoma patients were analyzed for intereye asymmetry of signals, and these data were compared with the asymmetry values of the healthy volunteers.
Results
Multiple recording channels significantly enhanced the recording of signals from parts of the visual field not reliably sampled with a single channel technique in all healthy volunteers, particularly along the horizontal meridian (P < 0.001). Signal amplitude did not decline with age in healthy volunteers. Recordings showed good reproducibility within individuals. In all 30 glaucoma patients, the Humphrey visual field defects were well demonstrated by the VEP, and topographic location was strongly correlated (rs = 0.79). Despite large interindividual variations in amplitude, scotomas were well demonstrated when compared with normal values. In the patients with suspected glaucoma, smaller changes in signal amplitude could be identified in parts of the field still normal on perimetry using intereye asymmetry analysis.
Conclusions
The multifocal, multichannel VEP can objectively detect glaucomatous visual field defects. The nasal step region can be more reliably tested using multiple channels. Asymmetry analysis has the potential to detect early defects. This technique represents a significant step toward the clinical application of objective perimetry in glaucoma.
Manuscript no. 99289.
aSave Sight Institute, Department of Ophthalmology, Sydney University, Sydney, Australia
Correspondence to Stuart L. Graham, FRACO, FRACS, Save Sight Institute, Sydney Eye Hospital, Macquarie Street, P.O. Box 1614, Sydney 2001, Australia
☆ Supported in part by research grants from Ophthalmic Research Institute of Australia, Alcon Australia and the National Health and Medical Research Council (NHMRC) (grant no.: 9937518). Dr. Klistorner is a Sydney Medical Foundation research fellow.
ABSTRACT