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Joe L. Wheat, Michael Twa; Comparison of Flicker Defined Form Perimetry Thresholds and Standard Achromatic Perimetry Thresholds in Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5502.
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© ARVO (1962-2015); The Authors (2016-present)
Standard automated perimetry (SAP) has been the gold standard for glaucoma testing, but other forms of perimetry using different stimuli have demonstrated differing sensitivity levels to glaucomatous optic neuropathy. One recently developed instrument, the Heidelberg Edge Perimeter (HEP) uses a flicker-defined-form stimulus instead of the standard achromatic stimuli used in SAP. The purpose of this experiment is to compare standard automated perimetric sensitivities to flicker defined form perimetric sensitivities in subjects with known glaucomatous optic neuropathy.
Twenty-four glaucoma subjects and fourteen control subjects were tested on with HEP and SAP using the standard testing protocols for each. Paired t-tests were used to evaluate the differences between mean deviations and pattern standard deviations for HEP and SAP. Significant depressions were plotted by location on the standard 24-2 test pattern for each instrument to demonstrate differences in depressions from glaucomatous field defects detected by the differing stimuli.
The average age of control subjects was 60 +/-10.21 and glaucoma subjects was 45 +/- 14.20. The 95% confidence intervals for mean deviations were as follows: HEP control subjects, +1.16 to -1.70 dB; SAP control subjects, +0.37 to -0.87 dB; HEP glaucoma subjects, -4.45 to -7.75 dB, SAP glaucoma subjects, -0.71 to -2.26 dB. The paired t-test for SAP and HEP revealed no significant difference between mean deviations for controls, but significant differences were detected between pattern standard deviations for controls, and between mean deviations for glaucoma subjects. Pattern standard deviations for glaucoma subjects approached but did not reach 0.05% significance. HEP showed a larger number and deeper depressions from control values for glaucoma subjects than demonstrated with SAP.
The expanded and lower confidence interval of the HEP mean deviations suggest it may reveal visual field abnormalities with glaucoma at earlier stages. Location mapping of significant depressions would seem to reveal larger defects and more significant depressions detected with HEP than revealed with SAP. The increased sensitivity to glaucomatous damage would seem to imply a different dynamic range for flicker defined form than for achromatic stimuli.
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