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MT Nicolela, TA McCormick, RP LeBlanc, PH Artes, BC Chauhan; Effects of Refractive Blur and Repeat Testing on Thresholds Determined by Frequency Doubling Technique . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2147.
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Purpose:To evaluate the effects of refractive blur and test repetition on the threshold values of frequency doubling technique (FDT) Methods:13 patients with open angle glaucoma and 11 control subjects (mean age of 53.9 and 52.9 years respectively) were enrolled. One randomly selected eye was tested on two sessions (different days) using the N-30 programme. In session 1, a learning test using the appropriate correction was performed initially, followed by tests with +6, +3, 0, -3 and –6 D of blur, performed in a random order. In session 2, six sequential tests were performed, using always the patients’ distance correction. In both sessions there was a rest period of approximately 5 minutes between the tests. Tests were performed under dim ambient illumination, but room lights were turned on between tests. Results:Results from session 2 showed a significant decrease in mean sensitivity with sequential testing (Fig. 1). After correcting the threshold values obtained in session 1 for the order effect extrapolated from session 2 (pointwise correction), a significant decrease in mean sensitivity was observed with progressive hyperopic or myopic blur (Fig. 2). Sequential testing and blur affected glaucoma and control subjects similarly. The effect of blur was similar in central and peripheral points and it was not affected by the baseline sensitivity value. Conclusion:FDT sensitivities decrease progressively with sequential testing. Refractive blur also affects FDT sensitivities, suggesting that ametropic patients should be tested with their distance correction. View OriginalDownload SlideView OriginalDownload Slide
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