Ganglion cell and retinal nerve fiber layer thickness predict the development of visual field damage in glaucoma suspects

Retinal Nerve Fiber Layer Thickness Measurements With Scanning Laser Polarimetry Predict Glaucomatous Visual Field Loss KOUROSH MOHAMMADI, MD, CHRISTOPHER BOWD, P H D, ROBERT N. WEINREB, MD, FELIPE A. MEDEIROS, MD, PAMELA A. SAMPLE, P H D, AND LINDA M. ZANGWILL, P H D ● PURPOSE: To assess whether baseline retinal nerve fiber layer (RNFL) measurements obtained with a scan- ning laser polarimeter, the GDx Nerve Fiber Analyzer, (Laser Diagnostic Technologies Inc., San Diego, Califor- nia) are predictive of development of repeatable glauco- matous visual field damage in glaucoma suspect eyes. ● DESIGN: Cohort study. ● METHODS: Participants were recruited from the UCSD longitudinal Diagnostic Innovations in Glaucoma Study (DIGS). One eye from each of 160 glaucoma suspects with normal standard automated perimetry (SAP) visual fields at baseline was studied. Study eyes were divided into convert and nonconvert groups based on the devel- opment of three consecutive glaucomatous visual fields during follow-up. SLP parameters, IOP, vertical cup disk ratio, stereophotograph assessment as glaucoma or nor- mal, corneal thickness, and visual field indices were included in univariate and multivariate Cox proportional hazards models to determine which SLP RNFL and ocular parameters were predictive of visual field conver- sion. ● RESULTS: Sixteen (10%) eyes developed repeatable visual field damage (converts) and 144 (90%) did not (nonconverts). Mean (95%CI) follow-up time until vi- sual field conversion for convert eyes was 2.7 (1.7, 3.6) years. Mean total follow-up of nonconvert eyes was 3.8 (3.5, 4.1) years. Four out of thirteen examined baseline SLP parameters and baseline SAP Mean Deviation (MD), SAP Pattern Standard Deviation (PSD), and Accepted for publication May 26, 2004. From the Hamilton Glaucoma Center, Department of Ophthalmology, University of California, San Diego, La Jolla, California. This study was supported by NIH EY 11008 (L.M.Z.), NIH 5 M01 RR00827 (K.M.), NIH EY 08208 (P.A.S.), and Foundation for Eye Research (F.A.M.) Inquiries to Linda Zangwill, P H D, Hamilton Glaucoma Center and Department of Ophthalmology, Diagnostic Imaging Laboratory, Univer- sity of California at San Diego, La Jolla, CA 92093-0946; fax: (858) 534-1625; e-mail: zangwill@eyecenter.ucsd.edu 2004 BY glaucomatous stereophotograph assessment were signifi- cant univariate predictors of visual field conversion. In multivariate models adjusted for age, IOP and CCT, SLP parameters inferior ratio, ellipse modulation, and UCSD linear discriminant function (LDF) were significant pre- dictors of visual field conversion. When SAP PSD and stereophotograph assessment were also included in the multivariate model inferior ratio and UCSD LDF re- mained independently predictive of visual field loss. ● CONCLUSIONS: Thinner baseline SLP RNFL measure- ments were independent predictors of visual field damage. In addition to thinner SLP RNFL measurements, higher baseline SAP PSD, and baseline glaucomatous stereo- photograph assessment each contributed to an increased risk of the development of abnormal visual fields in glaucoma suspect patients. SLP RNFL measurements were independently predictive of future visual loss even when age, IOP, CCT, vertical cup disk ratio, and SAP PSD were included in the model. (Am J Ophthalmol 2004;138:592– 601. © 2004 by Elsevier Inc. All rights reserved.) B Y THE TIME GLAUCOMATOUS VISUAL FIELD LOSS IS detected by standard automated perimetry (SAP), there may be a loss of a significant percentage of retinal ganglion cells. 1,2 Using photography and computer- assisted optical imaging techniques, optic disk damage in glaucoma suspects has been observed before the develop- ment of visual field defects measured by standard achro- matic perimetry. 2,3 Additionally, one study using photography to evaluate the optic disk and RNFL, indi- cated that RNFL damage precedes optic disk damage, suggesting that the condition of the RNFL might be a more sensitive indicator of glaucoma than optic disk topogra- phy. 4 Scanning laser polarimetry (SLP) is an optical imaging technology developed to diagnose and monitor glaucoma by E LSEVIER I NC . A LL RIGHTS RESERVED . doi:10.1016/j.ajo.2004.05.072