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Norman P. Einhorn, Peter Derr, Matthew Emmer; Evaluate Multi-channel Short Duration-tvep Response To Field Loss As A Result Of A Cerebral Vascular Attack. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6097.
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To quantify the asymmetries between occipital lobes of a population who have suffered a cerebral vascular attack (CVA) and a population with no history of CVA.
We tested 5 subjects with the SD-tVEP that had no history of CVA and 5 subjects who have hemianopic field loss due to CVA. Test duration was 20 seconds binocular (OU). Synchronized multi-channel SD-tVEP were recorded using a Diopsys NOVA System (Diopsys, Inc., Pine Brook, New Jersey, USA), which generated a time series of 240 data points per analysis window. Three checkerboard patterns were used in the study ranging from 15’ to 60’ in octave steps. In addition a flash pattern stimulus was presented. The Michelson contrast was set to 85 percent. The Left occipital lobe (LH) and Right occipital lobe (RH) VEPs was measured 5cm lateral to Oz (Mid). The following information was identified from the filtered N75-P100-N135 complex: LH Delta P100-N75 amplitude, RH P100-N75 amplitude and Mid P100-N75 amplitude. A ratio was established for each stimulus presented. The ratio compared the occipital lobe with the largest amplitude to the occipital lobe with smallest amplitude.
The subjects who were free of CVA showed good symmetry between the left and right occipital lobe VEP for all pattern VEPs and Flash. The ratios ranged from 50% to 97%. For all patterns and flash responses, the ratios were all greater than 50% for all individuals with no history of CVA. The subjects who had a history of CVA showed an asymmetry on at least one of the pattern VEP or flash VEP. The ratios of the significant asymmetries ranged from 4% to 46%. The table shows separation in the ratios between the non-CVA (Normal 1 -5) and CVA (CVA 1-5) subjects.
The ratios comparing occipital lobe amplitudes based on stimulus presented showed good separation between subjects suffering and not suffering from CVA. The multichannel SD-tVEP was able to show correlation between known anatomical damage as a result of CVA and VEP response to the corresponding cortical area. Our goal is to use the device to quickly monitor response to treatment.
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