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C.A. Johnson, K. Kent, S. Demirel; The Influence of Optical Media Opacities on Humphrey Matrix Frequency Doubling Technology (FDT) Perimetry Results . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3740.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the influence of optical media opacities on sensitivity and reliability for Frequency Doubling Technology (FDT) perimetry results using the 24–2 threshold test procedure of the Humphrey Matrix device. Methods: One eye of four subjects with normal visual function and ocular examinations in both eyes were evaluated with the Humphrey Matrix 24–2 threshold test procedure on six occasions: two baseline tests and four evaluations with successive levels of optical diffusion (reducing high contrast visual acuity to 20/32 (0.2 logMAR), 20/100 (0.7 logMAR), 20/160 (1.2 logMAR) and 20/320 (2.4 logMAR)). Optical diffusers consisted of plastic sheets that were combined into 1 to 4 layers to produce the various levels of optical diffusion. The average luminance of the display was 100 cd/m2 for the non–diffuser condition, and varied by less than 10% for the tests with optical diffusers in place. Contrast was reduced by 33%, 50%, 56% and 60% for the successive diffuser conditions. The 24–2 test procedure (ZEST threshold strategy) was employed for all tests. Results: There was a statistically significant (p<.0002) reduction in mean deviation (MD) from 2.62 dB for the non–diffuser condition to –1.76 dB, –12.03 dB, –15.61 dB and –23.19 dB for the successive diffuser tests, whereas there was no significant change in the pattern standard deviation (PSD) and glaucoma hemifield test (GHT) values. There were no differences in the rate of false positive errors, false negative errors or fixation losses among the various test conditions, nor was there any significant difference in test time. Conclusions: Our findings demonstrate that optical diffusers that simulate media opacities produce widespread generalized sensitivity losses throughout the central visual field for FDT perimetry evaluations, but no significant localized sensitivity changes. These findings are similar to previous reports of the effects of cataract on FDT test results. Reliability indices and testing time do not appear to show appreciable changes for different levels of optical diffusion. These findings should be helpful to clinicians in evaluating whether optical or neural factors contribute to FDT test results in clinic patients.
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