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Br J Ophthalmol 2004;88:1142-1145 doi:10.1136/bjo.2003.036756
  • Clinical science
    • Scientific reports

Sensitivity and specificity of scanning laser polarimetry using the GDx

  1. S Munkwitz1,
  2. J Funk1,
  3. K U Loeffler2,
  4. U Harbarth3,
  5. S Kremmer4
  1. 1Department of Ophthalmology, Albert-Ludwigs-University, Freiburg, Germany
  2. 2Department of Ophthalmology, University of Bonn, Bonn, Germany
  3. 3Laser Diagnostic Technologies (LDT) Europe, Schriesheim, Germany
  4. 4Department of Ophthalmology, University of Essen, Essen, Germany
  1. Correspondence to: Professor Dr J Funk Albert-Ludwigs-University, Killianstr. 5, Freiburg 79106, Germany; funkaug.ukl.uni-freiburg.de
  • Accepted 1 February 2004

Abstract

Background/aims: To determine the sensitivity and the specificity of the GDx in the detection of (1) advanced glaucoma, (2) early glaucoma, and (3) nerve fibre bundle defects (NFBD).

Methods: Group A comprised 20 eyes with reproducible glaucomatous visual field defects confirmed by octopus perimetry, group B consisted of 10 eyes with normal visual fields but either glaucomatous NFBD or deterioration of the disc over time clearly visible upon flicker comparison, and group C included 16 eyes with glaucomatous or non-glaucomatous NFBD clearly visible on red free photographs. Forty four eyes of 22 healthy volunteers served as controls. The GDx printouts of all subjects were evaluated by three independent observers in a masked fashion and without the clinical picture of the optic disc. Two of the three observers (SK, UH) were GDx experts, one (KUL) was an untrained GDx user.

Results: Among the GDx experts, sensitivity/specificity was 100%/100% (SK) and 90%/100% (UH) in detecting advanced glaucoma, and 100%/100% (SK) and 90%/100% (UH) in detecting early glaucoma. The sensitivity in detecting NFBD was only 37.5% (SK and UH). For the untrained GDx user the corresponding values were 50%/100% (group A), 20%/100% (group B), and 12.5%/91% (group C).

Conclusion: Detection of (early) glaucoma damage by the GDx, evaluated by trained experts, can be extremely high. To optimise its benefit in clinical routine training in interpreting GDx printouts is highly recommended. Detection of localised NFBD is crucial, even for experts.

Footnotes

    Responses to this article

    • Subjective evaluation of GDX printout detects asymmetric glaucoma
      • Paul J Harasymowycz
      Br J Ophthalmol published online September 14, 2009
    • Analysis of GDx printout
      • Stefano Da Pozzo,
      • Pierluigi Iacono
      Br J Ophthalmol published online September 14, 2009

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