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Editors Selection IGR 16-4
Visual Function and Structure: Determining progression with GDX-VCC
Comment by Chris Leung on:
23954 Detection of progressive retinal nerve fiber layer loss in glaucoma using scanning laser polarimetry with variable corneal compensation, Medeiros FA; Alencar LM; Zangwill LM et al., Investigative Ophthalmology and Visual Science, 2009; 50: 1675-1681
Retinal nerve fiber layer (RNFL) imaging with scanning laser polarimetry has been shown to be clinically useful for the detection of RNFL damage in glaucoma, although its role in monitoring progression has not been well-established. Medeiros et al. (675) performed an elegant study demonstrating the use of the GDx VCC scanning laser polarimeter in detecting progressive RNFL reduction in 195 patients with a diagnosis of glaucoma or glaucoma suspect over a median follow-up of 4 years. Using a linear mixed model, they reported that the rate of RNFL reduction was -0.7 μm/year in patients with progression evident in stereophotograph (based on masked comparisonbetween baseline and most recent photograph by two observers) and/or standard automated perimetry (by Humphrey Field Analyzer Guided Progression Analysis, GPA).
Measuring the RNFL thickness with digital imaging instruments is likely to become a new paradigm for the objective assessment of glaucoma progressionPatients with no progression on stereophotograph or perimetry also showed RNFL reduction (-0.14 μm/year), suggesting that loss of RNFL may precede detectable changes in the optic disc or visual field. However, most patients (72%) recruited at the time of study were glaucoma suspects with ocular hypertension and/or suspicious looking optic discs. It is difficult to discriminate disease progression from physiological loss in this group of patients. Glaucoma patients in this study had only mild disease (median visual field MD -4.08dB, first quartile: -6.44dB, third quartile: -2.14 dB). Further investigation is needed to evaluate the performance of GDx VCC in detecting RNFL decline in moderate and advanced glaucoma. This landmark study laid the foundations for using RNFL thickness for the evaluation of glaucoma progression. With the availability of the GDx GPA software, RNFL progression can now be analyzed using trend-based or event-based approaches for individual patients.Measuring RNFL thickness with digital imaging instruments is likely to become a new paradigm for the objective assessment of glaucoma progression.
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