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P. J. Mackenzie, C. A. Johnson, D. C. Gritz, S. R. Krishnadas, S. L. Mansberger; Predictive Value of Heidelberg Retinal Tomography and Frequency Doubling Technology Perimetry for Detecting Glaucoma in a Developing Country. Invest. Ophthalmol. Vis. Sci. 2008;49(13):743.
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To determine the diagnostic sensitivity of Heidelberg Retinal Tomography (HRT) in combination with Frequency Doubling Technology Perimetry (FDT) for detecting glaucoma in rural villages of a developing country.
A cross-sectional design was used. Testing included HRT, FDT perimetry (C-20-5 screening protocol), tonometry, anterior segment biomicroscopy, and dilated ophthalmoscopy in 307 rural, non-English speaking residents ofSouthern India over 35 years old. An abnormal HRT was defined as at least one area of borderline abnormality on the Moorfield's Regression Analysis. An abnormal FDT was defined as one location of reduced sensitivity present on both the initial and repeat examination. Diagnostic precision of HRT and FDT were compared to a cup to disk ratio of 0.7 or greater as determined on the clinical examination.
A reliable HRT scan was obtained in one eye in 95% of 248 subjects. 62% of subjects had reliable scans in both eyes. Repeatably reliable FDT's were obtained on 79% of subjects. For HRT, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for a C/D > 0.7 on clinical examination was 34%, 88%, 29%, 91% and 82% respectively. For FDT, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy was 26%, 78%, 14%, 89% and 72% respectively. When HRT and FDT were combined (either test abnormal), the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy was 46%, 72%, 20%, 90% and 69% respectively.
Both HRT and FDT can be used to obtain reliable data in a developing country rural village setting. In this setting, both tests perform significantly more poorly than in clinical settings. HRT and FDT appear to detect abnormality in different individuals with minimal overlap. Combined HRT and FDT testing leads to increased sensitivity, but with a substantial decrease in specificity, limiting its application as a screening tool in this population.
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