Sleep and circadian differences between light and heavy adult alcohol drinkers.

BACKGROUND: Numerous studies have reported that eveningness is associated with increased alcohol consumption. However, biological markers of circadian timing, such as dim light melatonin onset (DLMO) and circadian photoreceptor responsivity (post-illumination pupil response, PIPR), have rarely been assessed in the context of habitual alcohol consumption. This study aimed to examine sleep, circadian timing, and photoreceptor responsivity in adult alcohol drinkers. METHODS: Participants (21 to 45 years) included 28 light and 50 heavy drinkers. The 8-day study consisted of a week of ad lib sleep monitored with wrist actigraphy, followed by a 9-h laboratory session with a photoreceptor responsivity and circadian phase assessment. RESULTS: The heavy drinkers obtained on average 28 more minutes of sleep (p = 0.002) and reported more eveningness than the light drinkers (p = 0.029). There was a trend for a shorter DLMO-midsleep interval (p = 0.059) in the heavy drinkers, reflecting a tendency for them to sleep at an earlier circadian phase. The PIPR in the heavy drinkers was significantly smaller than in the light drinkers (p = 0.032), suggesting reduced circadian photoreceptor responsivity in the heavy drinkers. A larger PIPR was significantly associated with a later DLMO in the light drinkers (r = 0.44, p = 0.019), but this relationship was absent in the heavy drinkers (r = -0.01, p = 0.94). CONCLUSIONS: These results are consistent with earlier reports of more eveningness and a shorter DLMO-midsleep interval being associated with heavier alcohol drinking. The novel finding of reduced circadian photoreceptor responsivity in heavy drinkers is consistent with prior rodent studies. Future studies should explore the impact of habitual alcohol consumption on other measures of circadian photoreceptor responsivity.

Is melanopsin activation affecting large field color-matching functions?

Color theory is based on the exclusive activation of cones. However, since the discovery of melanopsin expressing cells in the human retina, evidence of its intrusion in brightness and color vision is increasing. We aimed to assess if differences between peripheral or large field and foveal color matches can be accounted for by melanopsin activation or rod intrusion. Photopic color matches by young observers showed that differences between extrafoveal and foveal results cannot be explained by rod intrusion. Furthermore, statistical analyses on existing color-matching functions suggest a role of melanopsin activation, particularly, in large field S fundamentals.

Temporal integration of rod signals in luminance and chromatic pathways.

We assessed how rod excitation (R) affects luminance (L + M + S) and chromatic [L/(L + M)] reaction times (RTs). A four-primary display based on the overlapped images of two spectrally modified monitors, which allowed specific or combined [L + M + S + R, L/(L + M) + R] photoreceptor stimulation, was used to present a C-target stimulus differing from the background only by the selected stimulation. For the luminance pathway, rod input increased RTs, suggesting a suppressive rod-cone interaction. The responses of the chromatic pathway were faster when rods were involved, suggesting a major role of rods in mesopic color perception.

Comparing flickering and pulsed chromatic pupil light responses.

The pupil light reflex (PLR) can serve as a biomarker of the photoreceptor function. Protocols for chromatic PLR consider mostly pulsed stimulation. A more sophisticated and promising technique is based on the PLR to flickering stimulation. Our aim was to compare flickering PLR (fPLR) and pulsed PLR (pPLR) parameters to validate the fPLR paradigm. Two different experiments were carried out in young participants to compare parameters of chromatic pupillary measurements under flickering and pulsed conditions. We found that the fPLR amplitude parameter was significantly associated with the pPLR transient constriction parameter. Also, for some conditions, pulse parameters can be identified directly in the fPLR recordings.

Alcohol subjective responses in heavy drinkers: Measuring acute effects in the natural environment versus the controlled laboratory setting.

BACKGROUND: For decades, laboratory alcohol challenges have been the "gold standard" for measuring individual differences in alcohol's subjective effects. However, these approaches are expensive and labor-intensive, making them impractical for large-scale use. This study examined the reliability and validity of a new high-resolution EMA (HR-EMA) ambulatory approach to assessing alcohol use and subjective responses in drinkers' natural environments. METHODS: Participants were 83 young adult heavy social drinkers (58% male; mean ± SD age = 25.4 ± 2.6 years) who completed up to two smartphone-based, 3-h HR-EMA assessments of alcohol use and related subjective responses in their typical drinking environments. Reported alcohol consumption during the HR-EMA periods was used to calculate estimated blood alcohol concentration (eBAC). Subjective effects were measured using the Brief Biphasic Alcohol Effects Scale (B-BAES) and Drug Effects Questionnaire (DEQ). All participants also completed identical measures during a separate, 4 to 5-h laboratory session in which they received a 0.8 g/kg alcohol challenge. RESULTS: Most natural environment drinking episodes (87%) met or exceeded the threshold for binge drinking (final mean eBAC = 0.12 g/dl). Associations between reported alcohol use and subjective responses on the B-BAES and DEQ were strongest earlier in the drinking events, with fair reliability of reported subjective effects across two HR-EMA episodes (intraclass correlation [ICC] range = 0.46-0.49). There was fair-to-good correspondence between HR-EMA- and laboratory-derived subjective responses (ICC range = 0.49-0.74), even after accounting for differences in alcohol consumption and drinking context. Reported stimulating and rewarding alcohol effects were higher in the ambulatory than laboratory setting, and vice versa for sedating effects. CONCLUSIONS: This study supports the reliability and validity of smartphone-based HR-EMA to measure alcohol use and subjective responses in heavy drinkers' natural environments. These findings lend support to the use of ambulatory HR-EMA as a measure of alcohol subjective responses in risky drinkers when a laboratory protocol is not practical, feasible, or safe.

Optimizing methods to isolate melanopsin-directed responses.

The intrinsic melanopsin photoresponse may initiate visual signals that differ in spatiotemporal characteristics from the cone-opsin- and rhodopsin-mediated signals. Applying the CIE standard observer functions in silent-substitution methods can require individual differences in photoreceptor spectral sensitivities and pre-receptoral filtering to be corrected; failure to do so can lead to the intrusion of more sensitive cone processes with putative melanopsin-directed stimuli. Here we evaluate heterochromatic flicker photometry (HFP) and photoreceptor-directed temporal white noise as techniques to limit the effect of these individual differences. Individualized luminous efficiency functions (V(λ)) were compared to the CIE standard observer functions. We show that adapting chromaticities used in silent-substitution methods can deviate by up to 54% in luminance when estimated with the individual and standard observer functions. These deviations lead to inadvertent cone intrusions in the visual functions measured with melanopsin-directed stimuli. To eliminate the intrusions, individual HFP corrections are sufficient at low frequencies (∼1Hz) but temporal white noise is also required at higher frequencies to desensitize penumbral cones. We therefore recommend the selective application of individualized observer calibration and/or temporal white noise in silent-substitution paradigms when studying melanopsin-directed photoresponses.

Dry Eye Symptoms in Individuals With Keratoconus Wearing Contact Lenses.

OBJECTIVES: To assess dry eye symptoms associated with different contact lens modalities in patients with keratoconus using a dry eye questionnaire. METHODS: An online survey was distributed by the National Keratoconus Foundation. The survey asked participants to report demographic characteristics, current optical correction, age at the time of diagnosis of keratoconus, and contact lens history. The 12-item Ocular Surface Disease Index (OSDI) questionnaire was also completed. Data from participants wearing the same contact lens modality bilaterally were analyzed. RESULTS: The survey was completed by 197 individuals wearing the same contact lens modality bilaterally. The average age of participants at the time of the survey was 47.2±14.8 years (range: 15-87 years), and the average age at which keratoconus was diagnosed was 26.1±9.9 years (range: 8-55 years). The mean overall OSDI score of all participants was 40.2±22.8 (range: 0-100). There was no difference in the mean OSDI scores based on current contact lens modality type (F=1.79; n=187; P=0.13). Based on an OSDI score of 33 or higher, 90% of participants reported symptoms indicative of dry eye disease. Scleral lens wearers reported less discomfort on the individual items related to windy and low-humidity conditions. CONCLUSIONS: Individuals with keratoconus, irrespective of contact lens modality, report a high incidence of dry eye symptoms.

The Feasibility, Tolerability, and Safety of Administering a Very High Alcohol Dose to Drinkers with Alcohol Use Disorder.

INTRODUCTION: There remains a paucity of research quantifying alcohol's effects in drinkers with alcohol use disorder (AUD), particularly responses to very high alcohol doses (≥0.8 g/kg). As drinkers with AUD frequently engage in very heavy drinking (8 to 10 drinks/occasion), doses of ≤0.8 g/kg may lack ecological validity. The present study examined the feasibility, tolerability, and safety of administering a very high alcohol dose (1.2 g/kg) to non-treatment-seeking AUD participants. METHODS: Sixty-one young adult AUD drinkers enrolled in the Chicago Social Drinking Project and completed 3 laboratory sessions at which they consumed a beverage with 1.2, 0.8, and 0.0 g/kg alcohol. Physiological responses (vital signs, nausea and vomiting, breath alcohol concentrations [BrAC]) were monitored throughout the sessions. After each session, participants completed a next-day survey of substance use, engagement in risky behaviors, and related consequences. RESULTS: Overall, the sample demonstrated good compliance with study procedures; 93% of participants adhered to presession alcohol abstinence requirements (indicated by BrAC < 0.003 g/dl), with no participants exhibiting serious alcohol withdrawal symptoms at arrival to study visits. The 1.2 g/kg alcohol dose achieved an expected mean peak BrAC of 0.13 g/dl at 60 minutes after drinking, which was well tolerated; the majority of the sample did not experience nausea (70%) or vomiting (93%), and dose effects on vital signs were not clinically significant. Finally, we demonstrated that the 1.2 g/kg alcohol dose is safe and not associated with postsession consequences, including reduced sleep time, atypical substance use, accidents or injuries, and severe hangovers. CONCLUSION: Results support the feasibility, tolerability, and safety of administering a very high alcohol dose to young adult drinkers with AUD within the context of a well-validated laboratory alcohol challenge paradigm. Utilizing an alcohol dose more consistent with naturalistic drinking patterns may foster greater ecological validity of laboratory paradigms for persons with moderate to severe AUD.

Exposure to JUUL use: cue reactivity effects in young adult current and former smokers.

BACKGROUND: Exposure to the use of first, second and third generations of electronic cigarettes (e-cigarettes) elicits the desire to vape and smoke among observers, as well as facilitates smoking behaviour. Given the rapid rise in the popularity of the pod mod JUUL, we examined whether observing the use of this device would elicit similar responses in smokers. Exploratory analyses were also conducted to determine whether JUUL can act as a smoking cue for former smokers. METHODS: The sample consisted of 82 young adult participants (62 current smokers and 20 former smokers approximately 1 year smoke free). The study examined their response to observing use of bottled water (control cue) and JUUL (active cue) in a controlled laboratory paradigm. Both cues were delivered by a trained study confederate under the guise of a social interaction task, and participants completed mood and desire and urge surveys precue and postcue exposures. RESULTS: In current smokers, exposure to the JUUL cue increased smoking urge and desire for a cigarette, mod/vape pen and JUUL, and two-thirds chose to smoke in the behavioural analogue task. In former smokers, the JUUL cue evoked modest and transient increases in desire for a cigarette and JUUL. CONCLUSIONS: The use of JUUL affects the user and elicits responses in observers; this study is the first to demonstrate that exposure to JUUL use may act as a smoking cue and exposure to JUUL use may affect tobacco control efforts.

Chromatic discriminations along two cardinal axes share a common attentional resource.

Attentional modulation is specific to either luminance or chromatic contrast discrimination, implying separate attentional resources for processing luminance and chromatic information processing [e.g., Curr. Biol.12, 1134 (2002)CUBLE20960-982210.1016/S0960-9822(02)00921-1]. However, there are two distinct visual pathways that process chromatic information: the parvocellular (PC) and koniocellular (KC) pathways. It is unclear whether there are separate attentional resources modulating the chromatic processes in these pathways. Here, we examined the attentional modulation effects on chromatic contrast discrimination with chromaticities along the $l$l or $s$s cardinal axis on a cone chromaticity space for preferentially stimulating either the inferred PC or KC pathway, respectively. A dual-task interference paradigm was used, and chromatic contrast discrimination sensitivities under dual-task conditions were compared with that under a single-task condition. The results revealed that compared with the single-task condition, attending to a competing central task in the dual-task condition decreased the peripheral discrimination sensitivity in both chromatic cardinal axes, and sensitivity reduced regardless of whether the dual tasks were along the same or different chromatic cardinal axes. These findings indicate that attentional effects on chromatic processes are not specific to the cardinal axis, suggesting that the PC and KC pathways may share a common attention resource in modulating chromatic processing.

Keratoconus Patient Satisfaction and Care Burden with Corneal Gas-permeable and Scleral Lenses.

SIGNIFICANCE: Scleral lenses (SLs) are increasingly being considered as the initial correction for patients with keratoconus. In this study, keratoconus patients report higher levels of comfort and visual satisfaction with SL compared with corneal gas-permeable lenses (GPs). PURPOSE: This study aimed to compare patient satisfaction and care burden associated with GP and SL for the management of keratoconus. METHODS: An electronic survey was distributed by the National Keratoconus Foundation from October 2016 to March 2017. Age at diagnosis, initial and current treatment, lens complications, access to care, lens handling time, and annual out-of-pocket treatment costs were collected. Vision, lens comfort, and ease of use satisfaction were rated from 1 to 5. RESULTS: A total of 422 responses were received, including 75 bilateral GP and 76 bilateral SL wearers. Scleral lens wearers had greater satisfaction with vision (3.2 ± 1.1 [SL] vs. 2.6 ± 1.1 [GP]; P < .001) and comfort (3.3 ± 1.0 [SL] vs. 2.2 ± 1.2 [GP]; P < .001) but similar ease of use satisfaction in both groups (2.8 ± 1.1 [SL] vs. 2.7 ± 1.1 [GP]; P < .90). Both groups reported issues with cloudy or foggy vision (GP, 63%; SL, 58%) and contact lens discomfort (GP, 77%; SL, 67%). Although GP wearers reported more issues with lens movement or loss (40 [GP] vs. 18% [SL]), they had fewer difficulties with halos (53 vs. 72% [SL]) and lens handling (40%) compared with SL wearers (63%). Gas-permeable lens (48%) and SL (45%) wearers spend 6 to 10 minutes daily handling their lenses. Sixty percent of GP wearers reported annual out-of-pocket cost expenses less than U.S.$1000, whereas only 41% of SL wearers reported the same. CONCLUSIONS: Scleral lens wearers with keratoconus report greater satisfaction with vision and comfort than do GP wearers, although both groups reported cloudy vision and lens discomfort.

Second Generation Electronic Nicotine Delivery System Vape Pen Exposure Generalizes as a Smoking Cue.

Introduction: Second generation electronic nicotine delivery systems (ENDS; also known as e-cigarettes, vaporizers or vape pens) are designed for a customized nicotine delivery experience and have less resemblance to regular cigarettes than first generation "cigalikes." The present study examined whether they generalize as a conditioned cue and evoke smoking urges or behavior in persons exposed to their use. Methods: Data were analyzed in N = 108 young adult smokers (≥5 cigarettes per week) randomized to either a traditional combustible cigarette smoking cue or a second generation ENDS vaping cue in a controlled laboratory setting. Cigarette and e-cigarette urge and desire were assessed pre- and post-cue exposure. Smoking behavior was also explored in a subsample undergoing a smoking latency phase after cue exposure (N = 26). Results: The ENDS vape pen cue evoked both urge and desire for a regular cigarette to a similar extent as that produced by the combustible cigarette cue. Both cues produced similar time to initiate smoking during the smoking latency phase. The ENDS vape pen cue elicited smoking urge and desire regardless of ENDS use history, that is, across ENDS naїve, lifetime or current users. Inclusion of past ENDS or cigarette use as covariates did not significantly alter the results. Conclusions: These findings demonstrate that observation of vape pen ENDS use generalizes as a conditioned cue to produce smoking urge, desire, and behavior in young adult smokers. As the popularity of these devices may eventually overtake those of first generation ENDS cigalikes, exposure effects will be of increasing importance. Implications: This study shows that passive exposure to a second generation ENDS vape pen cue evoked smoking urge, desire, and behavior across a range of daily and non-daily young adult smokers. Smoking urge and desire increases after vape pen exposure were similar to those produced by exposure to a first generation ENDS cigalike and a combustible cigarette, a known potent cue. Given the increasing popularity of ENDS tank system products, passive exposures to these devices will no doubt increase, and may contribute to tobacco use in young adult smokers.

Evidence for an impact of melanopsin activation on unique white perception.

Current models of human color vision only consider cone inputs at photopic light levels, yet it is unclear whether the recently discovered melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) contribute to color perception. Using a lab-made five-primary photostimulator that can independently control the stimulations of rods, cones, and ipRGCs in human retina, we determined the observer's unique white perception, an equilibrium point for signals arising from the opponent mechanisms of color vision, under different levels of melanopsin activation. We found changing melanopsin activation levels shifts the equilibrium point in the chromatic pathways. Our results suggest potential evidence for an impact of melanopsin activation on unique white perception and the existing color vision model for the periphery may need to be revised by incorporating melanopsin signaling.

Cone and melanopsin contributions to human brightness estimation: reply.

Our analytical description of full-field brightness perception data [J. Opt. Soc. Am. A35, B19 (2018)JOAOD60740-323210.1364/JOSAA.35.000B19] with contributions from cone luminance and melanopsin expressing intrinsically photosensitive retinal ganglion cells has been extended [J. Opt. Soc. Am. A35, 1780 (2018)JOAOD60740-323210.1364/JOSAA.35.001780] to include S-cones through a blue-yellow opponent channel. We welcome this reanalysis and provide a few remarks on the approach.

Extrinsic cone-mediated post-receptoral noise inhibits the rod temporal impulse response function.

We determined how extrinsic white noise correlating with cone inputs to the three primary visual pathways affects both rod-pathway temporal contrast sensitivity and the impulse response function. A four-primary photostimulator provided independent control of rod and cone photoreceptor excitations under mesopic illumination (20 photopic Td). We show that rod-pathway temporal contrast sensitivity uniformly decreases across all temporal frequencies in the presence of cone noise correlating with the inferred magnocellular, parvocellular, or koniocellular pathways. The rod-pathway temporal impulse response functions derived using the Stork-Falk procedure (with a minimum phase assumption) had lower amplitudes in the pathway-specific cone noise. Therefore, cone noise impairs rod-pathway temporal contrast sensitivity without delaying rod-pathway signal transmission.

Cone and melanopsin contributions to human brightness estimation.

We determined the contributions of cone and melanopsin luminance signaling to human brightness perception. The absolute brightness of four narrowband primary lights presented in a full-field Ganzfeld was estimated in two conditions, either cone luminance-equated (186.7-1,867.0 cd·m-2) or melanopsin luminance-equated (31.6-316.3 melanopsin cd·m-2). We show that brightness estimations for each primary light follow an approximately linear increase with increasing cone or melanopsin luminance (in log units), but are not equivalent for primary lights equated with either cone or melanopsin luminance. Instead, brightness estimations result from a combined interaction between cone and melanopsin signaling. Analytical modeling with wavelength-dependent coefficients signifies that melanopsin luminance positively correlates with brightness magnitudes, and the cone luminance has two contribution components, one that is additive to melanopsin luminance and a second that is negative, implying an adaptation process. These results provide a new framework for evaluating the physiological basis of brightness perception and have direct practical applications for the development of energy-efficient light sources.

COMPARISON OF VISUAL AND ANATOMICAL OUTCOMES OF EYES UNDERGOING TYPE I BOSTON KERATOPROSTHESIS WITH COMBINATION PARS PLANA VITRECTOMY WITH EYES WITHOUT COMBINATION VITRECTOMY.

PURPOSE: To determine whether 1-year visual and anatomical results after surgery combining pars plana vitrectomy, Boston keratoprosthesis, and a glaucoma drainage device as needed are similar, better, or worse than Boston keratoprosthesis initial implantation alone. METHODS: We performed a retrospective review of adult patients undergoing Boston keratoprosthesis at our institution. Visual acuity outcomes, anatomical results, and complication rates of patients undergoing combination surgery (including pars plana vitrectomy and a posterior glaucoma drainage device) were compared with those undergoing keratoprosthesis placement alone. RESULTS: There were 70 eyes in the keratoprosthesis alone group and 55 eyes in the keratoprosthesis with pars plana vitrectomy group. Mean follow-up durations were 54.67 months in the keratoprosthesis alone group and 48.41 months in the combination group. Baseline mean Snellen equivalent visual acuities were worse for the combination group compared with the keratoprosthesis alone group (P = 0.027). Visual acuities improved postoperatively by 1 month after keratoprosthesis implantation for both groups and improved three or more lines of Snellen acuity in the majority of eyes for both groups (≥72% by 12 months). Eyes undergoing pars plana vitrectomy had lower rates of de novo (P = 0.015) and significantly lower rates of secondary procedures (P = 0.002) at 1 year. One year complications rates for retroprosthetic membrane formation, retinal detachment, hypotony, cystoid macular edema, epiretinal membrane formation, endophthalmitis, and corneal melting were similar for both groups. CONCLUSION: Compared with keratoprosthesis alone, combining keratoprosthesis with pars plana vitrectomy and a glaucoma drainage device as needed, resulted in lower rates of de novo glaucoma, lower rates of additional surgical procedures, similar visual acuity outcomes at 1 year, and did not result in higher complication rates.

Macaque retinal ganglion cell responses to visual patterns: harmonic composition, noise, and psychophysical detectability.

The goal of these experiments was to test how well cell responses to visual patterns can be predicted from the sinewave tuning curve. Magnocellular (MC) and parvocellular (PC) ganglion cell responses to different spatial waveforms (sinewave, squarewave, and ramp waveforms) were measured across a range of spatial frequencies. Sinewave spatial tuning curves were fit with standard Gaussian models. From these fits, waveforms and spatial tuning of a cell's responses to the other waveforms were predicted for different harmonics by scaling in amplitude for the power in the waveform's Fourier expansion series over spatial frequency. Since higher spatial harmonics move at a higher temporal frequency, an additional scaling for each harmonic by the MC (bandpass) or PC (lowpass) temporal response was included, together with response phase. Finally, the model included a rectifying nonlinearity. This provided a largely satisfactory estimation of MC and PC cell responses to complex waveforms. As a consequence of their transient responses, MC responses to complex waveforms were found to have significantly more energy in higher spatial harmonic components than PC responses. Response variance (noise) was also quantified as a function of harmonic component. Noise increased to some degree for the higher harmonics. The data are relevant for psychophysical detection or discrimination of visual patterns, and we discuss the results in this context.

Luminance and chromatic signals interact differently with melanopsin activation to control the pupil light response.

Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin. These cells receive afferent inputs from rods and cones, which provide inputs to the postreceptoral visual pathways. It is unknown, however, how melanopsin activation is integrated with postreceptoral signals to control the pupillary light reflex. This study reports human flicker pupillary responses measured using stimuli generated with a five-primary photostimulator that selectively modulated melanopsin, rod, S-, M-, and L-cone excitations in isolation, or in combination to produce postreceptoral signals. We first analyzed the light adaptation behavior of melanopsin activation and rod and cones signals. Second, we determined how melanopsin is integrated with postreceptoral signals by testing with cone luminance, chromatic blue-yellow, and chromatic red-green stimuli that were processed by magnocellular (MC), koniocellular (KC), and parvocellular (PC) pathways, respectively. A combined rod and melanopsin response was also measured. The relative phase of the postreceptoral signals was varied with respect to the melanopsin phase. The results showed that light adaptation behavior for all conditions was weaker than typical Weber adaptation. Melanopsin activation combined linearly with luminance, S-cone, and rod inputs, suggesting the locus of integration with MC and KC signals was retinal. The melanopsin contribution to phasic pupil responses was lower than luminance contributions, but much higher than S-cone contributions. Chromatic red-green modulation interacted with melanopsin activation nonlinearly as described by a "winner-takes-all" process, suggesting the integration with PC signals might be mediated by a postretinal site.

Eye movements and the neural basis of context effects on visual sensitivity.

The effects of context on visual sensitivity are well established (e.g., sensitivity to luminance flicker is substantially higher on mean-gray surrounds than on white or black surrounds). The neural mechanisms generating context effects, however, remain unresolved. In the absence of direct tests, some theories invoke enhancement of edges by lateral inhibition, whereas others rely on transients caused by miniature eye movements that maintain fixation. We first replicated the luminance results on human observers and found unexpectedly that sensitivity to red-green flicker is also affected by surround color, being substantially higher on mean-gray surrounds than on red or green surrounds. To identify the neural bases of both context effects, we used in vivo electrophysiological recordings of primate magnocellular and parvocellular ganglion cell responses to luminance and red-green modulations, respectively. To test neuronal sensitivity to stationary edge contrast, neuronal responses were measured at various distances from the modulation edge against various surrounds. We found no evidence of enhanced responses to stationary edges on any surrounds, ruling out lateral inhibition-type explanations. To simulate the effects of eye movements, target patches were abruptly displaced while measuring responses. Abruptly displaced edges evoked vigorous transient responses that were selective for modulation-phase on mean-gray surrounds, but were phase-invariant on other surrounds. Eye movements could thus enhance detection of flicker on mean-gray surrounds, and neurometric analyses supported a primary role for eye movements in enhancing sensitivity. In addition, the transformation of spatial edges to transient neuronal responses by eye movements provides the signals for detecting luminance and color edges in natural scenes.