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M.G. Todorova, A.M. Palmowski–Wolfe, S. Orguel, J. Flammer, M. Brigell; Multi–Flash MfERG in Primary Open–Angle Glaucoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1662.
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© ARVO (1962-2015); The Authors (2016-present)
To analyse the sensitivity of the multifocal electroretinogram (mfERG) to detect glaucomatous dysfunction in normal tension (NTG) and high tension (HTG) primary open angle glaucoma (POAG) patients using a special multi–flash stimulation technique.
MfERGs were recorded from 22 POAG patients with glaucomatous visual field defects (MD>2.0 dB): 13 NTG (mean age 55.2 (SD 7.3); MD 5.3) and 9 HTG patients (mean age 56.8 (SD 9.7); MD 5.5) and compared to those of 13 controls (mean age 49.3 (SD 13.2)). The mfERG stimulus array consisted of 103 hexagons displayed on a monochrome monitor (frame rate: 75Hz, frame duration: 13.33ms). Each stimulus started with an m–sequence step (m–sequence: 2^13, Lmax: 200cd/m2, Lmin: 1cd/m2), followed by two global flashes (L: 200cd/m2) at an interval of ∼26ms. Signals were bandpass filtered: 10–300Hz.
Focal scalar products (SP) were analyzed using focal templates derived from the first 12 controls recorded (VERIS 4.8). We analyzed the response to the m–sequence step at 0–45ms and of the following two components induced by the global flashes at 40–70ms (I1) and at 70–105ms (I2). For each epoch examined, retinal function was considered significantly altered, when more than 5 of the 103 focal areas had a z–score of > +2/< –2.
Nine of 13 NTG (69%) and 6 of 9 HTG patients (67%) had more than 5 reduced SP areas in at least one epoch examined. Most changes occurred in the induced components. The control group showed significant changes only in the oldest (increased SP of I1, 18 areas) and the youngest subject (increased SP of I2, 34 areas). In NTG the m–sequence response was significantly reduced in 2 patients (average: 22.5 areas) and increased in 2 patients. I1 was significantly reduced in 5 patients (average: 16 areas) and increased in 3 patients, while I2 was significantly reduced in 7 patients (average: 11 areas) and increased in none. In HTG the m– sequence response was significantly reduced in 4 patients (average: 6.75 areas) and increased in 1 patient. I1 was significantly reduced in 4 patients (average: 16 areas) and increased in none, while I2 was significantly reduced in 3 patients (average: 12 areas) and increased in 2 patients. The number of increased responses was not significantly different between patients and controls whereas the number of decreased observations was significantly higher for POAG patients than for controls (p<0.001, 2x4 contingency table, Fisher's exact test).
Therefore, this stimulus sequence holds promise for the diagnosis of early functional changes in POAG and may have a potential to furthermore separate HTG from NTG.
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