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M Wang, EE Sutter, RL Stamper, CM Poloschek; Preliminary Evaluation of a Multi-focal Electroretinogram Protocol for Glaucoma . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2153.
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Purpose: The optic nerve head component (ONHC) is a contribution to the multi-focal electroretinogram (mfERG) that originates from ganglion cell fibers near the optic nerve head. Our aim is to evaluate a stimulation protocol designed to enhance the ONHC in a small group of normals, glaucoma suspect and patients with early and advanced primary open angle glaucoma (POAG). Methods: MfERGs were recorded from 3 glaucoma suspect patients, 2 early POAG patients, 2 advanced POAG patients, and 6 control subjects with a VERIS ScienceTM 4 system. The stimulus array consisted 103 hexagonal patches presented on a high luminance monochrome monitor (frame rate 75/sec). The stimulation sequence consisted of multi-focal, m-sequence encoded flashes presented at 67 ms intervals with two interleaved global flash stimuli at 26.6ms and 53.2ms after the multi-focal stimuli. The intensity of the multi-focal and global flashes was 2.7 cdsec/m2. Pupils were dilated and a Burian-Allen electrode was used for signal derivation. The ONHC was extracted as the effect of the focal stimulus on the second global flash. MfERG results were compared with Humphrey visual fields (central 30-2 threshold protocol). Results: Normal group:We obtained ONHC contributions in each normal subject. Glaucoma suspect:All three patients in this group had normal visual fields. Two exhibited a strong ONHC contribution while the third one showed unilateral loss in the eye with the larger cup/disc ratio. Early glaucoma:The visual fields of all patients in this group were within the normal range. In all patients, the ONHC appeared to be subtantially reduced. Advanced glaucoma:The ONHC was barely detectable and absent in the regions of deep scotomas. Conclusion: The results suggest that with the global flash protocol the mfERG is a promising tool for the evaluation of optic nerve fiber function in glaucoma. Losses in the ONHC were seen before anomalies in the visual field can be detected. The technique may be especially useful for screening of glaucoma suspects and management of patients with early glaucoma. An evaluation of the technique on larger cohorts of patients and normals is indicated.
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