May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
The Repeatability of the Heidelberg Retina Tomograph Glaucoma Probability Score and Its Usefulness as an Index of Progression
Author Affiliations & Notes
  • N. G. Strouthidis
    Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom
  • C. Zuniga-Cossio
    Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom
  • D. F. Garway-Heath
    Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom
  • Footnotes
    Commercial Relationships N.G. Strouthidis, Heidelberg Engineering, F; C. Zuniga-Cossio, Heidelberg Engineering, F; D.F. Garway-Heath, Heidelberg Engineering, Carl Zeiss Meditec, F; Carl Zeiss Meditec, C.
  • Footnotes
    Support None.
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 3329. doi:
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      N. G. Strouthidis, C. Zuniga-Cossio, D. F. Garway-Heath; The Repeatability of the Heidelberg Retina Tomograph Glaucoma Probability Score and Its Usefulness as an Index of Progression. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3329.

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

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Abstract

Purpose:: To evaluate the inter-visit, inter-observer repeatability of the Glaucoma Probability Score (GPS) and to compare its ability to monitor glaucomatous progression with established visual field (VF) progression strategies.

Methods:: 1) Heidelberg Retina Tomograph (HRT) ‘Classic’ inter-visit, inter-observer test-retest data from 74 subjects (Br. J. Ophthalmol. 2005;89;1427-1432) were analysed in HRT-3 Explorer software to generate the global GPS. Variance was related to the GPS, so repeatability coefficients (RCs) were calculated for 3 GPS bins (0-19%, 20-79% and 80-100%).2) 198 OHT and 21 control subjects were examined longitudinally (1993-2001) using regular HRT (‘Classic’) and VF testing. 5 or more HRT and VF tests were available for each subject. GPSs were generated in HRT-3 Explorer software. Linear regression of global GPS over time was performed for each subject, with significance p < 0.05. Criteria for estimates of specificity were: 1) significant deterioration of GPS over time in controls and 2) significant improvement of GPS over time in all subjects. The number of OHT subjects significantly deteriorating was compared to a VF pointwise linear regression strategy with similar specificity.

Results:: There was good GPS repeatability for the 0-19% and 80-100% bins, at RC = 0.4% and 4.3%, respectively. However, in the 20-79% bin, repeatability is poor with RC = 13.5%.Estimated specificity (95% confidence intervals) was 95.2% (76.1 - 99.9%) for GPS criterion 1 and 96.8% (93.2 - 98.6%) for GPS criterion 2. 25 OHT subjects were identified as progressing. VF progression was identified in 11 of these subjects. 26 OHT subjects were progressing by VF alone.

Conclusions:: GPS scores between 20 and 79% are variable and should be interpreted with caution. Despite this, linear regression of GPS over time achieved a good specificity, with positive detection rates similar to other HRT progression algorithms at the same level of specificity (Invest Ophthalmol Vis Sci. 2006;47:2904-2910). Agreement (proportions progressing by GPS and VF) was also similar to previous reports.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • optic disc 
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