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Sophie A. Kramer, Anna Polunina, Margarita G. Todorova, Andreas Schötzau, Selim Orguel, Anja M. Palmowski-Wolfe; A new Global Flash Paradigm Multifocal Electroretinogram (mf-ERG) In The Diagnosis Of Early Retinal Dysfunction In Glaucoma. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5482.
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© ARVO (1962-2015); The Authors (2016-present)
To test a new 2 flash multifocal electroretinogram (mfERG) paradigm in glaucoma using a reduced light intensity of the m-sequence stimulus as opposed to the global flash, as it has been suggested that this may increase the responses induced by the global flash, which has been the part of the mfERG response where most changes have been noted in glaucoma.
A mfERG was recorded from 20 primary open angle glaucoma (POAG) patients (15 NTG, 5 HTG) and compared to the recordings of 20 control subjects. A binary m-sequence (2^13) was used (Lmax 100cd/m2, Lmin <1cd/m2), followed by two global flashes (200cd/m2) at an interval of 26ms (VERIS 6.0TM, FMSIII). The array consisted 103 hexagons. Retinal signals were amplified (gain = 50K) and bandpass filtered at 1-300Hz. Focal scalar products (SP) were calculated using focal templates derived from the control recordings. We analyzed 5 larger response averages (central 7.5 deg. and 4 adjoining quadrants) as well as 8 smaller response averages (central 4 deg. and 7 surrounding response averages of approximately 7 deg. each). Three epochs were analyzed: the direct component at 15-45ms (DC) and the following two components induced by the effects of the preceding focal flash on the response to the global flashes at 45-75ms (IC-1) and at 75-105ms (IC-2). Statistical analysis was performed using linear mixed effects models in the statistical package R version 12.1.
Responses differed significantly between POAG and control in all response averages. Control subjects had significantly larger central than peripheral responses. No such effect of location was seen in POAG. Control responses differed more, when the smaller response averages were analyzed (p<0.001). While these observations held true for all response epochs analyzed, the DC differed less and the IC-2 most when POAG was compared to control. These observations also held true when HTG and NTG were analyzed separately, HTG and NTG did not differ from one another. For POAG, the best sensitive discriminatory power could be shown in the IC-2 of the central 4 deg. with an area under the ROC curve of 0.85. With a cutoff value of 1.99nV/deg2, 85% of the POAG (100% HTG, 80% NTG) were correctly classified as abnormal while 85% of the control subjects were correctly classified as normal.
In the 2 global flash mfERG, sensitivity and specificity to glaucomatous damage could be increased by decreasing the luminance of the m-sequence flash from 200 to 100cd/m2.
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