December 2002
Volume 43, Issue 13
Free
ARVO Annual Meeting Abstract  |   December 2002
Correction of corneal polarization axis and magnitude improves discriminating ability of GDx Nerve Fiber Analyzer (GDx)
LM Zangwill; C Bowd; DS Greenfield; RN Weinreb
Author Affiliations & Notes
  • LM Zangwill
    Glaucoma Center Ophthalmology University of California San Diego La Jolla CA
  • C Bowd
    Glaucoma Center Ophthalmology University of California San Diego La Jolla CA
  • DS Greenfield
    Ophthalmology Bascom Palmer Eye Institute Miami FL
  • RN Weinreb
    Glaucoma Center Ophthalmology University of California San Diego La Jolla CA
  • Footnotes
    Commercial Relationships   L.M. Zangwill, None; C. Bowd, None; D.S. Greenfield, Laser Diagnostic Technologies F; R.N. Weinreb, Laser Diagnostic Technologies R. Grant Identification: Support: NIH Grant EY11008
Investigative Ophthalmology & Visual Science December 2002, Vol.43, 930. doi:
  • Views
  • Share
  • Tools
    • Alerts
      User Alerts
      You are adding an alert for:
      Correction of corneal polarization axis and magnitude improves discriminating ability of GDx Nerve Fiber Analyzer (GDx)
      You will receive an email whenever this article is corrected, updated, or cited in the literature. You can manage this and all other alerts in My Account
      The alert will be sent to:
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation
      Citation

      LM Zangwill, C Bowd, DS Greenfield, RN Weinreb; Correction of corneal polarization axis and magnitude improves discriminating ability of GDx Nerve Fiber Analyzer (GDx) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):930.

      Download citation file:

      © ARVO (1962-2015); The Authors (2016-present)

      ×
    • Get Permissions
  • Supplements
Abstract

Abstract: : Purpose: The GDx Nerve Fiber Analyzer measures retinal nerve fiber layer birefringence and compensates for corneal birefringence using a fixed corneal polarization axis (CPA) (15 degrees nasally downward) and fixed corneal polarization magnitude (CPM) (60 nm).To determine whether correction for CPA and CPM improves the discriminating ability of the GDx. Methods: The GDx was modified to enable the measurement of CPA and CPM so that compensation for corneal birefringence is eye specific. 52 normal eyes and 55 eyes with repeatable glaucomatous visual field damage (average MD = -6.5 + 4.9 dB) were examined using both fixed compensation GDx and GDx with variable corneal compensation (GDx VCC). Results: Mean (+ SD) CPA was 24.4 + 17.2 degrees (range -13 to 74 degrees). Mean CPM was 40.1 nm + 15.3 nm (range 7 to 91 nm). After adjusting for age, there was no statistically significant difference in CPA or CPM between normal and glaucoma eyes. There was no significant correlation between CPA and CPM (p ≷ .05). The mean average RNFL thickness measured using the fixed compensation GDx and GDx VCC was 59.0 microns and 41.0 microns in glaucoma patients, and 70.7 microns and 47.7 microns in normal subjects, respectively. The area under the ROC curve for discriminating between normal and glaucoma eyes improved using the GDx VCC for some but not all GDx parameters. For ellipse modulation the ROC area improved from .68 using fixed compensation GDx to .82 using GDx VCC. Other parameters for which the area under the ROC curve improved by ≷ 0.08 from fixed compensation GDx to GDx VCC included total polar integral (.73 versus .83), inferior integral (.75 versus .85), ellipse average (.75 versus .84), inferior average (.77 versus .85), nasal average (.57 versus .67), and several temporal thickness parameters. The area under the ROC curve for "the GDx number", superior maximum, inferior maximum and nasal maximum did not differ between fixed compensation GDx and GDx VCC. Conclusion: Correction for CPA and CPM improves the discriminating ability of many GDx nerve fiber layer parameters.

Keywords: 430 imaging/image analysis: clinical • 356 clinical (human) or epidemiologic studies: systems/equipment/techniques 
© 2002, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Permission to republish any abstract or part of an abstract in any form must be obtained in writing from the ARVO Office prior to publication.
Copyright © 2025 Association for Research in Vision and Ophthalmology.
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×
This site uses cookies. By continuing to use our website, you are agreeing to our privacy policy.Accept