Poststimulus response characteristics of the human cone flicker electroretinogram.

At certain temporal frequencies, the human cone flicker electroretinogram (ERG) contains multiple additional responses following the termination of a flicker train. The purpose of this study was to determine whether these poststimulus responses are a continuing response to the terminated flicker train or represent the oscillation of a resonant system. ERGs were recorded from 10 visually normal adults in response to full-field sinusoidally modulated flicker trains presented against a short-wavelength rod-saturating adapting field.

Equivalent intrinsic noise, sampling efficiency, and contrast sensitivity in patients with retinitis pigmentosa.

Purpose: To determine the relationships among equivalent intrinsic noise (Neq), sampling efficiency, and contrast sensitivity (CS) in patients with retinitis pigmentosa (RP), where Neq is an estimate of the amount of noise within the visual pathway and sampling efficiency represents the subject's ability to use stimulus information optimally.

Methods: Participants included 10 patients with RP aged 10 to 54 years, who had visual acuities of 20/40 or better, and 10 visually normal control subjects aged 22 to 65 years. CS was measured for 2-cycles-per-degree Gabor patch targets presented in the absence of noise (CS0) and in five levels of noise spectral density.

Electroretinographic findings in a patient with congenital stationary night blindness due to a novel NYX mutation.

Purpose: To document a novel NYX gene mutation in a patient with X-linked complete congenital stationary night blindness and to describe this patient's electroretinogram (ERG) characteristics.

Methods: ERGs were recorded from a 17-year-old male with a previously unreported NYX mutation (819G > A) that results in a missense codon change (Trp237Ter). ERGs were recorded in response to brief-flash stimuli, 6.

Characteristics of late negative ERG responses elicited by sawtooth flicker.

Background: This study aimed to determine whether the properties of the late negative responses (LNRs) of the electroretinogram (ERG) elicited by sawtooth flicker are consistent with the characteristics of the photopic negative response generated by a light pulse (PhNRpulse).

Methods: ERG recordings were obtained from 10 visually normal individuals and from 6 patients with optic atrophy (OA) in response to 8-Hz rapid-on and rapid-off sawtooth flicker and to brief (4 ms) light pulses. All stimuli were either long wavelength (R), middle wavelength (G), or a combination of equal luminances of long and middle wavelengths (Y) presented on a short-wavelength, rod-saturating adapting field.

Stimulus chromatic properties affect period doubling in the human cone flicker ERG.

Period doubling in the full-field cone flicker electroretinogram (ERG) refers to an alternation in waveform amplitude and/or shape from cycle to cycle, presumably owing to the operation of a nonlinear gain control mechanism. This study examined the influence of stimulus chromatic properties on the characteristics of period doubling in order to better understand the underlying mechanism. ERGs were acquired from 5 visually normal subjects in response to sinusoidally modulated flicker presented at frequencies from 25 to 100 Hz.

Object frequency characteristics of visual acuity.

Purpose: To examine the extent to which visual acuity (VA) for broadband optotypes is scale invariant by determining whether the same object frequencies mediate VA for individuals with different levels of VA.

Methods: LogMAR (minimum angle of resolution) VA for briefly presented tumbling E's was measured in 10 visually normal individuals and in five patients with VA loss. The E's were either unblurred or blurred with Gaussian low-pass filters that had cutoff frequencies spanning a 1.

Structural and functional measures of inner retinal integrity following visual acuity improvement in a patient with hereditary motor and sensory neuropathy type VI.

Purpose: To report measures of inner retinal integrity following improvement in visual acuity and visual fields in a patient with hereditary motor and sensory neuropathy type VI (HMSN VI).

Case Report: The patient is a Caucasian male with HMSN VI (type 2A Charcot-Marie-Tooth disease and associated optic atrophy) and a c.1090C→T (p.

Contributions of optical and non-optical blur to variation in visual acuity.

Purpose: To determine the relative contributions of optical and non-optical sources of intrinsic blur to variations in visual acuity (VA) among normally sighted subjects.

Methods: Best-corrected VA of 16 normally sighted subjects was measured using briefly presented (59 ms) tumbling E optotypes that were either unblurred or blurred through convolution with Gaussian functions of different widths. A standard model of intrinsic blur was used to estimate each subject's equivalent intrinsic blur (σint) and VA for the unblurred tumbling E (MAR0).

Autoantibodies in melanoma-associated retinopathy target TRPM1 cation channels of retinal ON bipolar cells.

Melanoma-associated retinopathy (MAR) is characterized by night blindness, photopsias, and a selective reduction of the electroretinogram b-wave. In certain cases, the serum contains autoantibodies that react with ON bipolar cells, but the target of these autoantibodies has not been identified. Here we show that the primary target of autoantibodies produced in MAR patients with reduced b-wave is the TRPM1 cation channel, the newly identified transduction channel in ON bipolar cells.

Harmonic analysis of the cone flicker ERG of rabbit.

Harmonic analysis was used to characterize the rabbit flicker ERG elicited by sinusoidally modulated full-field stimuli under light-adapted conditions. The frequency-response function for fundamental amplitude, derived from Fourier analysis of the ERG waveforms, exhibited two limbs, with an amplitude minimum at approximately 30Hz, and a high-frequency region peaking at around 45Hz and extending to more than 100Hz at higher adapting levels. At low frequencies (<20Hz), the fundamental response amplitude was independent of mean luminance (Weber law behavior), whereas the response amplitude at high stimulus frequencies varied nonlinearly with mean luminance.

Spatial contrast sensitivity in dynamic and static additive luminance noise.

The purpose of this study was to define the quantitative relationship between the temporal characteristics of additive luminance noise and the properties of the spatial contrast sensitivity function (CSF). CSFs were obtained from two observers using Gabor patch targets of short duration that were added to white luminance noise with a range of root-mean-square contrasts (c(rms)). The noise was either dynamic or static and was either of the same duration as the test target (synchronous) or of longer duration (asynchronous).

Determinants of contrast sensitivity for the tumbling E and Landolt C.

Purpose: To compare the object spatial frequencies that underlie contrast sensitivity for the tumbling E and Landolt C across a range of optotype sizes and under conditions biased toward the magnocellular (MC) and parvocellular (PC) pathways.

Methods: Contrast thresholds of two visually normal observers were measured using tumbling E optotypes that were either low-pass filtered or high-pass filtered with a two-dimensional Gaussian filter. Optotypes were presented using steady-pedestal and pulsed-pedestal paradigms to target the MC and PC pathways, respectively.

Characteristics of period doubling in the rat cone flicker ERG.

When the eye is stimulated by a flickering light, the electroretinogram (ERG) and other electrophysiological responses in the visual pathway often exhibit period doubling. This phenomenon is manifested as an alternation in the shape of the response waveform from cycle to cycle, and also as spectral components at the half-fundamental frequency (F/2) and its odd multiples. Although period doubling has been described in humans as well as in other animals, its features in the rodent flicker ERG have not been characterized.

Is there an omitted stimulus response in the human cone flicker electroretinogram?

Omitting a stimulus from a train of repetitive stimuli, by either interrupting or terminating the train, can elicit an electrophysiological response that occurs at the time appropriate for the omitted stimulus. This study investigated whether such an omitted stimulus response (OSR) is present in the flicker electroretinogram (ERG) of the human cone system. ERGs were recorded from 11 visually normal subjects in response to full-field sinusoidal flicker trains presented against a rod-desensitizing adapting field at frequencies ranging from 12.

Contrast thresholds in additive luminance noise: Effect of noise temporal characteristics.

This study investigated the way in which the temporal properties of additive luminance noise influence threshold contrast and affect estimates of equivalent noise and sampling efficiency. Threshold contrast was obtained from four visually normal observers for a 2-cycle-per-degree Gabor patch across a range of target durations in the absence and presence of additive luminance noise that was either static or dynamic. In addition, the temporal relationship between target and noise was either synchronous (simultaneous presentation of both) or asynchronous (noise duration longer than target duration).

Two distinct processes are evident in rat cone flicker ERG responses at low and high temporal frequencies.

The electroretinogram (ERG) provides a noninvasive, objective measure of retinal function, and is one of the most widely used diagnostic tools in the study of visual disorders. Although rodents are often used in the study of retinal disease, the properties of the flicker ERG of the rodent retina have not been fully characterized. Here, we show that the fundamental response of the rat ERG to sine-wave flicker exhibited a low-pass pattern in the frequency range from 2 to 30 Hz, whereas the second harmonic (F2) showed a more complex frequency-response relation.

Spatial frequencies used in Landolt C orientation judgments: relation to inferred magnocellular and parvocellular pathways.

The purpose of this study was to define the spatial frequencies that underlie judgments of Landolt C orientation under test conditions designed to favor either the magnocellular (MC) or parvocellular (PC) pathway. Contrast thresholds of two observers were measured for briefly presented Landolt Cs of four sizes, using steady- and pulsed-pedestal paradigms to bias performance toward the MC and PC pathways, respectively. Contrast thresholds were derived from a two-alternative forced-choice orientation judgment task using the QUEST procedure.

Comparison of spectral measures of period doubling in the cone flicker electroretinogram.

Purpose: Under certain conditions, the full-field flicker electroretinogram (ERG) of the cone system can show period doubling, such that the shape of the ERG waveform alternates from cycle to cycle. The purpose of this study was to determine the relationship between stimulus temporal frequency and the amplitudes of the spectral components of the ERG that correspond to period doubling.

Method: ERGs were recorded from 10 visually normal subjects in response to full-field sinusoidal flicker presented at frequencies ranging from 12.

Spontaneous improvement of rod system function in a patient with melanoma-associated retinopathy.

Purpose: To report spontaneous improvement of rod visual function in a patient with melanoma-associated retinopathy (MAR).

Methods: Electroretinography (ERG), and dark-adapted psychophysical thresholds were performed on a male patient with the MAR syndrome, during four visits over a period of almost 7 years.

Results: There was a spontaneous, subjective improvement in night vision and a decrease in the severity of photopsias of the patient's left eye between the initial and most recent visits.

Intersession repeatability of humphrey perimetry measurements in patients with retinitis pigmentosa.

Purpose: To determine the relationship between intersession test repeatability in static perimetry and the degree of local sensitivity reduction in patients with retinitis pigmentosa (RP).

Methods: Visual field data were obtained from 27 patients with RP using FASTPAC 30-2 of the Humphrey Field Analyzer and stimulus sizes III and V. Each test was repeated at two subsequent visits after an initial practice session.

Retinal thickness and visual thresholds measured in patients with retinitis pigmentosa.

Purpose: : To determine the association between retinal thickness and visual function in patients with retinitis pigmentosa (RP).

Methods: : Retinal thickness was estimated from optical coherence tomography (OCT) images obtained for six patients with RP. The thickness measurements were compared with dark-adapted rod and minimally light-adapted cone thresholds obtained by psychophysical testing using a Tübinger perimeter and with standard light-adapted Humphrey visual field (HVF) perimetric thresholds.

Effect of contrast on the frequency response of synchronous period doubling.

At temporal frequencies between approximately 30 and 70 Hz, the flicker electroretinogram (ERG) of the cone system can exhibit an alternation in response amplitude from cycle to cycle that has been termed synchronous period doubling. This phenomenon has been attributed to a nonlinear feedback mechanism at an early retinal locus. The purpose of the present study was to define the effect of stimulus contrast on period doubling in order to better understand the nature of the underlying mechanism.

Cone phototransduction and growth of the ERG b-wave during light adaptation.

The purpose of this study was to determine whether cone redepolarization accounts for the amplitude increase of the b-wave of the human electroretinogram (ERG) during light adaptation. The time course of the b-wave amplitude increase was compared to the time course of the change in the activation phase of cone phototransduction, as derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. ERG recordings were obtained from five visually normal subjects, alternately in the presence of the adapting field (adapt-on condition) and 300ms after its temporary extinction (adapt-off condition).

Activation phase of cone phototransduction and the flicker electroretinogram in retinitis pigmentosa.

This study examined the relationship between the activation phase of cone phototransduction and the flicker electroretinogram (ERG) in 15 patients with retinitis pigmentosa (RP) and 12 age-equivalent, visually normal control subjects. Values of Rmp3 (maximum amplitude of P3, the massed cone photoreceptor response) and S (sensitivity of cone phototransduction) were derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. Fundamental amplitude and phase of the flicker ERG were derived from responses to sinusoidal flicker presented at temporal frequencies ranging from 7.

Characteristics of period doubling in the human cone flicker electroretinogram.

Electroretinogram (ERG) responses of the cone system to a flickering stimulus can exhibit a cyclic variation in amplitude. This phenomenon of synchronous period doubling has been attributed to a nonlinear feedback mechanism within the retina that alters response gain. The aim of the present study was to investigate intersubject variability in period doubling in the ERG of the human cone system, and to assess the implications of this variability for signal processing within the retina.