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M.C. Geiman, S. Viswanathan, J.P. Ngan, V. Malinovsky; Multifocal Flash Electroretinogram in Primary Open Angle Glaucoma . Invest. Ophthalmol. Vis. Sci. 2003;44(13):33.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: This preliminary study examined whether multifocal flash electroretinogram (mFERG) responses can reveal localized changes in retinal function in patients with primary open angle glaucoma (POAG). Methods: mFERGs recorded with a VERIS system (Electro-diagnostic Imaging, CA) using DTL fiber electrodes from 10 POAG patients (42-80 yrs) were compared to those of age-matched controls from a group of 60 normal subjects (21-80 yrs). Their pupils were fully dilated; accommodation blocked and refractive errors corrected. The visual stimuli consisted of 103-scaled hexagons with a mean luminance 100cd/m 2 and 50% contrast. The entire stimulus array subtended 31 deg vertically and 37 deg horizontally at a viewing distance of 48 cms. The monitor frame rate was 75Hz, M-sequence exponent 15 with 1 frame/M-step and amplifier cut off frequencies 1 and 100Hz. Only the first order kernel was analyzed. Behavioral visual field sensitivity was measured with the Humphrey 30-2 test. Results: mFERGs of normal subjects showed naso-temporal variations in the relative heights of two positive potentials (P1 and P2) whose amplitudes were measured from the first negative trough N1. For the control subjects, while the amplitude of P1 was larger in the nasal field and decreased in size at locations equidistant from fixation in the temporal field, P2 amplitude did not show significant differences between nasal and temporal field locations. Consequently for each normal subject the P2/P1 ratio was lower in the nasal field compared to the ratios at comparable eccentricities in the temporal field. Relative to the amplitude ratios of age-matched controls, the ratios of POAG patients were significantly altered at many retinal locations taking values outside of 2 standard deviations from the mean ratios of control subjects in the respective age groups. These statistically significant alterations included most locations that showed significant changes on behavioral perimetric testing. In addition, several of these POAG patients showed significant ratio changes at visual field locations where behavioral sensitivity was essentially normal. Conclusions: mFERG responses with the above recording paradigm and analysis technique can demonstrate localized changes in retinal function in patients with POAG. There is a potential for mFERG in the detection and possibly in monitoring the progression of functional damage in glaucoma.
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