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M. Bach, A. Ramharter; Pattern Erg in Glaucoma: Comparison of the "Pergla" Paradigm and the "Perg–Ratio" Paradigm . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4664.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To detect early glaucoma, Porciatti & Ventura recently suggested a new PERG paradigm "PERGLA" with the following features: (1) skin rather than corneal electrodes, (2) steady–state reversal (16 rps) of horizontal 1.6 cpd gratings, and (3) Fourier–based analysis. We compared sensitivity and specificity to detect glaucoma of PERGLA with our "PERG–Ratio" paradigm. Methods: We examined 19 eyes with early to advanced glaucoma (age 59±5 yrs) and a control group (n=29, age 53±6 yrs). We employed the PERGLA–paradigm and also the "PERG–Ratio Paradigm", the latter uses (1) corneal (DTL) electrodes, (2) the same reversal rate, but 2 check sizes of 0.8° and 16°, and (3) Fourier–based analysis using the ratio of amplitudes to the 2 check sizes. Responses to all stimuli were recorded simultaneously with both electrode types. Results: The PERG amplitude to the gratings and 0.8° check stimuli were nearly identical in every eye, regardless of electrode type. The amplitudes obtained with skin were ∼40% of those with corneal electrodes. Signal–to–noise ratio of skin was 2/3 of corneal electrodes. The interindividual variability of both skin and corneal electrodes covered a range of 4. The test–retest coefficient of variation (CV) in normals, averaged across stimuli, was 14±4% for skin, and 11±2% for corneal electrodes. Discrimination of glaucoma patients was assessed via receiver operating characteristics (ROCs). Using skin electrodes, ROC area was 75/76/71% for gratings, checks or the PERG–ratio. Using skin electrodes, the ROC areas were 10% higher. Best performed the PERG–ratio with a sensitivity of 90% and a sensitivity of 88%. When selecting only early glaucoma cases, the sensitivity and specificity of the PERG–ratio were 10% above any obtained with single stimuli. Conclusions: Skin electrodes may be a valid alternative compared to corneal electrodes, as they avoid eye contact and reduce amplitude to only 40%. However, sensitivity and specificity are markedly lower when using skin rather than corneal electrodes. The PERG–ratio based on 2 widely different check sizes outperforms any single–stimulus paradigm, regardless of electrode type.
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