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V Porciatti, LM Ventura; Electrophysiological Screening for Glaucoma: Normative Data With a Non-invasive, Fast, and Fully Automatic Version of the Pattern ERG Called PERGLA . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3904.
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Purpose: The PERG has been shown to be altered in early stages of glaucoma  and predict future visual field losses . We have developed a simplified version of the PERG for screening and follow up of glaucoma, including monitoring of the effects of treatment, called PERGLA. Methods: The PERGLA is recorded simultaneously from both eyes by means of skin electrodes on the lower eyelids, in response to horizontal gratings (1.7 c/d, 25 deg circular field, 95% contrast, 100 cd/sqm mean luminance), alternating at 8.14 Hz. Signals are conventionally amplified and averaged. The actual test lasts 3 minutes (two blocks of 1.5 minutes each) and subjects are allowed to blink freely. The response is automatically analyzed by Discrete Fourier Transform to isolate the component corresponding to the pattern reversal rate. The response amplitude and phase (latency) are compared with a database of age-corrected, normative data, and deviations from normal average are expressed in SD units. The internal variability of the PERGLA and a noise response are also simultaneously evaluated. Results: Normative data (n=80 eyes) have been obtained in healthy subjects aged 12-85 years with normal optic disk and IOP. Typically, the signal exceeds the noise by a factor of 10 or more, and the coefficient of variation between partial averages is 10% for amplitude and 2% for phase. The test-retest variation in amplitude and phase is typically within 10% and 2%, respectively. Conclusion: The signal-to-noise ratio, reliability and reproducibility of the PERGLA are at least as good as other PERG techniques obtained with corneal electrodes. The use of non-corneal electrodes, automatic response evaluation, and expression of results in deviation from normal indicates a potential value for a simple screening and follow up of glaucoma in the early stages, and for the evaluation of the effects of pharmacological treatment.  Porciatti et al, Doc. Ophthalmol. 1987;  Pfeiffer et al, IOVS 1993.
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