The multi-focal electroretinogram (mfERG) acquires spatially resolved retinal signals that can facilitate diagnosis and treatment of visual disorders. However, much information contained in the recorded signals remains unexploited. Here, we use the mfERG to detect age-related changes in retinal recovery from a photopic double-flash response. mfERGs were recorded from 33 normal subjects with no ocular pathology (mean age: 39.4 years, range: 18.2 - 57.8 years) using the VerisPro software (EDI) that allows extraction of retinal responses at different inter-stimulus intervals (ISIs) and different flash combinations. 103 hexagons and 2.66cd sec/m^2 stimulus luminance were used. The responses were grouped into macular and peripheral retinal areas. In the macular region, the stimulus subtended a ~10 degrees radial area centered on the fovea with the central 1 degree excluded. The peripheral stimulus formed a ring with inner and outer radii ~10 and 20 degrees, respectively. Single-flash responses preceded by a double flash were extracted from the signal. Age-related changes in retinal recovery were found for the macular, but not peripheral retina at the minimum ISI (13.3ms). A t-test comparing the 10 youngest and the 10 oldest observers revealed a statistically significant difference (p<0.05, ?=0.05). For longer ISIs no difference was found. The results suggest that fast adaptation in the macular area is more vulnerable to aging than the peripheral area and that, for the age range covered here, the older retina has the capacity to fully recover between 13.3 and 26.6ms and respond like a young retina. These regional differences cannot be explained by pre-retinal factors. Meeting abstract presented at OSA Fall Vision 2012

Multifocal electrophysiology offers a collection of clinical tools to test the function of the retinocortical pathway. The multifocal electroretinogram provides specific information regarding bioelectrical responses up to the point where the signals leave the eye. The multifocal visual-evoked potential permits monitoring of the signals arriving at the visual cortex. Both techniques provide topographic maps that permit localization of dysfunction across the central 40–50° of the visual field. The article illustrates how different stimulation and analysis protocols are used to address specific clinical problems.

PURPOSE:To investigate the retinal responses generated by flash interactions in a recently introduced "global (full-screen) flash" stimulus paradigm to record the multifocal electroretinogram (mfERG).METHODS:Five normal individuals were studied with stimulation combining multifocal (pseudorandom) flashes with interleaved global (periodic, full-screen) flashes. The intensities of the two flashes were independently varied. Two distinct first-order response components were obtained: the mean response to the focal flashes (referred to as the direct response, DR) and the effect of the focal flash on the responses evoked by the global flash (the induced component, IC).RESULTS:Increasing the global flash luminance reduced DR amplitude and shortened DR implicit time. IC amplitude peaked with a moderate global flash (1.33-2.67 cd.s/m2). With a global flash of the right intensity, a weak focal flash could evoke a considerable IC even when the DR was barely detectable. Moderate global flashes maximized the IC, and its intersubject variability was reduced at lower focal flash luminances. IC topography had a large naso-temporal asymmetry.CONCLUSIONS:While the DR is the average response generated by the local flashes regardless of the context of preceding and following flashes, the IC represents the difference in the global flash response in the presence and absence of the preceding focal flash. As the focal flashes were always preceded by the periodically occurring global flashes, the DR reflects the resulting adapted or desensitized state of the retinal patch. The pure, nonlinear IC is thought to reflect predominantly inner retinal function.

PURPOSE. To determine age-related changes in retinal response dynamics derived from multifocal electroretinograms (mfERGs).METHODS. MfERG data were obtained from 70 subjects with normal phakic eyes, age 9 to 80 years. Whereas the first- and higher-order kernels resulting from the mfERG contain detailed information regarding the nonlinear response dynamics of the retina, they do not lend themselves directly to an easy and intuitive interpretation. To achieve a better appreciation of fast adaptive mechanisms and their changes with aging, regional averages of the kernel series were translated at different retinal eccentricities (0degrees-5degrees, 5degrees-15degrees, and 15degrees-25degrees) into responses generated in different contexts. Specifically, the effect of aging on responses to stimuli presented in isolation was compared with the effect on responses adapted by preceding stimuli ("forward" effect). The interference of the immediately following stimuli with the response generation ("backward effect") was also considered.RESULTS. Age-related changes were found in the isolated flash response as well as in the backward and forward interactions between consecutive flash responses. Larger fractional changes with age were found in response density than in implicit time, and the rate of change with age was larger for responses to isolated flashes than for responses adapted by preceding flashes.CONCLUSIONS. Senescent changes in the isolated flash response and in consecutive flash interactions derived from the binary kernel series indicate an aging process at an early stage in the visual system. Mechanisms of retinal adaptation may partially compensate for age-related reductions in the isolated flash response.

To assess local retinal function in patients with retinitis pigmentosa (RP), multi-focal ERGs and local thresholds (static visual fields) were obtained on eight RP patients with visual acuities of 20/25 or better. All e~ght patients showed multi-focal responses with normal timing within the central 5 deg. However, there were few responses with normal timing in the areas outside the central 7.5 deg, except in the case of the only patient with a 30 Hz full-field response with normal timing. Since full-field ERGs are dominated by responses from the periphery, this finding supplies a foundation for the commonly observed delays in the full-field cone ERGs of patients with RP. With respect to amplitude, only two patients showed multi-focal responses with near normal amplitudes anywhere in the field. The loss of amplitude at any point was not a good predictor of visual sensitivity in the Humphrey visual field. On the other hand, all areas with normal timing had near normal sensitivity. Timing changes appear to be an early indication of local retinal damage to the cone system. Ncarly all areas with sensitivity losses greater than 0.5 log unit, and some areas with near normal sensitivity, showed significantly delayed multi-focal ERGs. Finally areas with extreme sensitivity loss show multi-focal responses with a wide range of amplitudes and implicit times across patients, suggesting different mechanisms of disease action in different patients. © 1997 Elsevier Science Ltd

Purpose: We tested a prototype stimulator interfaced with a commercially available scanning laser ophthalmoscope designed to measure retinal capillary perfusion (Heidelberg Retina Flowmeter (HRF)). The add-on stimulator optically superimposed the image of a monitor display on to the subject's retina coaxially with the imaging optics of the HRF. The purpose of the study was to determine if flicker and pattern stimulation presented in this manner could evoke changes in retinal perfusion that could be measured by the HRF. Methods: The prototype stimulator projected 55° visual angle circular fields of homogeneous flicker, alternating checkerboard, and multi-focal m-sequence hexagonal patterns on the retina of 10 human subjects during acquisition of images by the HRF. Results: Images were successfully acquired and processed. HRF perfusion values during flicker and pattern stimulation were not significantly different from control values. Conclusions: Results of the present study and a previously published study showing a flicker-induced increase in the HRF perfusion values are contradictory. Retinal perfusion measured by the HRF were not affected by flicker and pattern stimulation delivered through the prototype device. These data are not consistent with a large flicker or pattern induced increase in retinal perfusion. The instrumental modification appears promising. However, the raster scan stimulation technique or some other aspect of stimulation or image acquisition may account for the different results in the present study and previous studies in our laboratory and in the laboratories of other investigators.

METHODS. MfERG data were obtained from 70 subjects with normal phakic eyes, age 9 to 80 years. Whereas the firstand higher-order kernels resulting from the mfERG contain detailed information regarding the nonlinear response dynamics of the retina, they do not lend themselves directly to an easy and intuitive interpretation. To achieve a better appreciation of fast adaptive mechanisms and their changes with aging, regional averages of the kernel series were translated at different retinal eccentricities (0°–5°, 5°–15°, and 15°–25°) into responses generated in different contexts. Specifically, the effect of aging on responses to stimuli presented in isolation was compared with the effect on responses adapted by preceding stimuli (“forward” effect). The interference of the immediately following stimuli with the response generation (“backward effect”) was also considered.

The multifocal electroretinogram (mfERG) allows for functional field mapping by concurrently deriving responses from a large number of retinal locations. The stimulus resolution most commonly used consists of 103 hexagonal elements. Here, we stimulated with an array of 509 elements. To determine the extent to which the multifocal ERG shows anatomical and physiological details, such as shadows cast by the retinal vasculature, we obtained mfERGs from two subjects using two different stimulus luminance levels and three light spectra. Good correspondence of some depressions with major blood vessels suggests relative angioscotomata. However, some reproducible local depressions cannot be attributed to blood vessel shadows cast on the retina, but more likely reflect local inhomogeneities in the physiological response characteristics.

To search for an optic nerve head component (ONHC) in the monkey’s (Macaca mulatta) multifocal electroretinogram (mERG), mERGs from three animals were recorded with different electrode configurations. A component with a latency that varied with distance from the optic nerve head was easily identified by eye in recordings from the speculum of a Burian–Allen electrode referenced to a DTL on the unstimulated eye. This component was reasonably well isolated by subtracting a weighted version of a Burian–Allen bipolar recording or by employing the extraction algorithm of Sutter and Bearse (1999, Vision Research, 39, 419–436). The waveform of this component resembles the ONHC reported for the human mERG. © 2001 Elsevier Science Ltd. All rights reserved.

This study examines ganglion cell dysfunction in glaucoma using a global flash multifocal ERG technique. The optic nerve head components and retinal components of patients were significantly affected, in different ways, compared to control eyes.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text E. E. Sutter, M. A. Bearse, R. L. Stamper, G. N. Lambrou, C. L. Percicot, R. Ofri, and D. Raz, "Monitoring Retinal Ganglion Cell Function with the MERG Recent Advances," in Vision Science and its Applications, A. Sawchuk, ed., Vol. 53 of OSA Trends in Optics and Photonics (Optica Publishing Group, 2001), paper FA4. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

This study examines the characteristics and the naso-temporal asymmetries of the higher-order oscillatory components of the multifocal electroretinogram (mERG). The magnitude of the mERG asymmetry and the mechanisms which produce it have not been studied previously. We recorded the mERG from seven normal observers using slow multifocal flicker and response filtering of 10–300 Hz. This permitted, without additional filtering, examination of the dominant first order component and the oscillation-rich components in the first and second order kernels. The oscillatory components in the two kernels had multiple peaks separated by about 6.8 ms, similar to those of conventional oscillatory potentials. Naso-temporal asymmetry of the three response components was analyzed in three groups (concentric rings around the fovea) spanning 1.5–10 deg of retinal eccentricity. The oscillation-rich components were, on average, approximately 14% larger in amplitude in the temporal retina than in corresponding nasal locations (p < 0.05) while the dominant first order component was not asymmetrically distributed. We tested the hypothesis that the asymmetry could be modeled as a combination of a retinal component (RC) and an optic nerve head component (ONHC) which varies in latency as a function of distance from the optic disc. We found that both oscillatory components and the dominant first order response could be decomposed into RCs and ONHCs that are symmetrically distributed. Thus, it appears that the naso-temporal asymmetries of the oscillation-rich components are produced primarily by the relative alignment and enhancement of RC and ONHC wavelets in the temporal retina, and misalignment and partial cancellation in the nasal retina.

Purpose: Small areas of retinal pathology may pose diagnostic difficulties. The noninvasive multifocal electroretinogram (MF-ERG) provides a topographical mapping of retinal function. Its role in the diagnosis of macular diseases is examined in age-related macular degeneration (AMD). AMD is a main cause of central visual loss in the elderly population, affecting the second eye in 75 %.

Multifocal electroretinograms (M-ERGs) recorded with the conventional flicker protocol originate predominantly from the distal retinal layers, that is, from receptors, bipolar cells and Mueller cells.

The human retina is able to perform over a luminance range of approximately 1:1010.