Senescent Changes and Topography of the Dark-Adapted Multifocal Electroretinogram.

Purpose: To investigate the topographic changes of the dark-adapted multifocal electroretinogram (mfERG) across adulthood in the central retina and compare the topography between macular versus extramacular, nasal versus temporal, and inferior versus superior retinal areas.

Methods: Sixty-five subjects (18-88 years) received a comprehensive dilated eye examination to ensure the health of their retina and were tested with a dark-adapted mfERG protocol using a 61-hexagon pattern. The lens absorption of each subject was also estimated using a heterochromatic flicker photometry (HFP) paradigm.

Multifocal visual evoked potentials are influenced by variable contrast stimulation in MS.

Objective: To test the hypothesis that patients with multiple sclerosis (MS) with intereye asymmetry on low contrast letter acuity, and thickness of the retinal nerve fiber layer (RNFL), would exhibit corresponding changes in cortical timing and amplitude responses on pattern reversal multifocal visual evoked potentials (mfVEP), contingent upon variable stimulus contrast.

Methods: In a cross-sectional study, we investigated a cohort of 11 normal subjects and 40 patients with MS, 21 of whom had a history of acute optic neuritis (MS-AON) with an intereye asymmetry with respect to RNFL thickness, and on low contrast letter acuity performance. Pattern reversal mfVEP was performed at high (100%), low (33.

Subclinical carriers and conversions in Leber hereditary optic neuropathy: a prospective psychophysical study.

Purpose: The authors previously presented the results of their 2001 field investigation to rural Brazil to investigate a 336-member pedigree of Leber hereditary optic neuropathy (LHON). The present work describes the yearly field investigations 2001 to 2005, utilizing a variety of highly sophisticated psychophysical and electrophysiologic procedures, in asymptomatic LHON carriers, some of whom converted to affected status.

Methods: Careful, repeated examinations of 75 carriers of homoplasmic 11778 LHON mtDNA J-haplogroup mutants were performed as part of the field investigation of this pedigree.

Muscimol and baclofen differentially suppress retinotopic and nonretinotopic responses in visual cortex.

This study relates to local field potentials and single-unit responses in cat visual cortex elicited by contrast reversal of bar gratings that were presented in single, double, or multiple discrete patch (es) of the visual field. Concurrent stimulation of many patches by means of the pseudorandom, binary m-sequence technique revealed interactions between their respective responses. An analysis identified two distinct components of local field potentials: a fast local component (FLC) and a slow distributed component (SDC).

The effect of fixation instability on the multifocal VEP.

In multifocal visually evoked potentials (mfVEP), we find reversals in waveform near the horizontal meridian due to convolutions in the cortex. This renders the mfVEP very sensitive to small changes in gaze position. In this study we tested the effects of very small amounts of fixation instability on the mfVEP topography under controlled conditions using four normal subjects.

Multifocal electroretinograms combined with periodic flashes: direct responses and induced components.

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.

Acute zonal occult outer retinopathy in a patient with graft-versus-host disease.

Purpose: To investigate the mechanism of bilateral central vision loss in a patient with graft-versus-host disease.

Design: Observational case report.

Methods: A 43-year-old man with graft-versus-host disease developed acute painless progressive central vision loss, first in the left eye and then in the right.

mfERG response dynamics of the aging retina.

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.

Multifocal electroretinography evaluation for early detection of retinal dysfunction in patients taking hydroxychloroquine.

Purpose: To evaluate macular function using multifocal electroretinography (mfERG) in a cohort of asymptomatic patients taking hydroxychloroquine and a patient with maculopathy secondary to hydroxychloroquine treatment.

Methods: mfERG recordings were obtained for both eyes of 11 patients taking hydroxychloroquine without clinical signs of toxicity and 1 patient with toxic maculopathy. Initially, the classic m-sequence paradigm for the first-order kernel (103 hexagons; 2.

Modification of the Heidelberg retinal flowmeter to record pattern and flicker induced blood flow changes.

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.

The fine structure of multifocal ERG topographies.

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.

Darkness beyond the light: attentional inhibition surrounding the classic spotlight.

The aim of the present investigation was to determine the nature and spatial distribution of selective visual attention. Using cortical source localization of ERP data corresponding to 60 task-irrelevant stimuli across the visual field, we assessed attention effects on visual processing. Consistent with previous findings, visual processing was enhanced at the attended spatial location.