Reduction In Pupil Size Research Articles

Mental effort during mindless reading? Pupil fluctuations indicate internal processing during levels of inattention.

Mind wandering, an experience characterized by a reduced external focus of attention and an increased internal focus, has seen significant theoretical advancement in understanding its underlying cognitive processes. The levels-of-inattention hypothesis posits that in mind wandering, external attention is reduced in a graded fashion, reflecting different levels of weak versus deep attentional decoupling. However, it has remained unclear whether internal processing during mind wandering, and mindless reading in particular, requires effort and, if so, whether it is graded or distinct. To address this, we analyzed pupil size as a measure of cognitive load in the sustained-attention-to-stimulus task during text reading. We examined whether decoupled external attention is linked to an overall reduction in workload and whether internal focus of attention is graded or represents a distinct cognitive process. Overall, overlooking errors in the text was associated with a small pupil size, indicating reduced effortful processing. However, this effect varied with error type: overlooking high- or medium-level errors (weak decoupling) resulted in reduced pupil size, while overlooking low-level errors (deep decoupling) had no effect on pupil size. Moreover, detecting an error (at any processing level) elicited a task-evoked pupillary response, which was absent when it was overlooked. These findings suggest that weak decoupling reduces internal resource-demanding processing and are in line with the hypothesis that large pupils during deep decoupling may be associated with distinct states of effortful internal processing. They further support both the levels-of-inattention hypothesis and the notion that internal focus is a distinct mode of deeply decoupled processing. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Pupil Response in Visual Tracking Tasks: The Impacts of Task Load, Familiarity, and Gaze Position.

Pupil size is a significant biosignal for human behavior monitoring and can reveal much underlying information. This study explored the effects of task load, task familiarity, and gaze position on pupil response during learning a visual tracking task. We hypothesized that pupil size would increase with task load, up to a certain level before decreasing, decrease with task familiarity, and increase more when focusing on areas preceding the target than other areas. Fifteen participants were recruited for an arrow tracking learning task with incremental task load. Pupil size data were collected using a Tobii Pro Nano eye tracker. A 2 × 3 × 5 three-way factorial repeated measures ANOVA was conducted using R (version 4.2.1) to evaluate the main and interactive effects of key variables on adjusted pupil size. The association between individuals' cognitive load, assessed by NASA-TLX, and pupil size was further analyzed using a linear mixed-effect model. We found that task repetition resulted in a reduction in pupil size; however, this effect was found to diminish as the task load increased. The main effect of task load approached statistical significance, but different trends were observed in trial 1 and trial 2. No significant difference in pupil size was detected among the three gaze positions. The relationship between pupil size and cognitive load overall followed an inverted U curve. Our study showed how pupil size changes as a function of task load, task familiarity, and gaze scanning. This finding provides sensory evidence that could improve educational outcomes.

Testing Pupil Size as a Possible Alternative Metric of Physical Fatigue in Automotive Manufacturing Tasks

This work investigates using pupil size to track changes in physical fatigue during manufacturing tasks. Participants completed an automotive manufacturing task over three trials. Impulse and peak force were recorded as ground-truth metrics of physical fatigue. Pupil size and blink rate were also recorded by means of a head-mounted eye-tracker. Impulse and peak force decreased between trial 1 and trial 3 suggesting an increase in fatigue. Interestingly, this was accompanied by a significant reduction in pupil size. No difference in blink rate was found. Our study adds to the literature on fatigue assessment suggesting pupil size as a future possible alternative metric for fatigue assessment in manufacturing Ergonomics.

Transcytosis-mediated anterograde transport of TrkA receptors is necessary for sympathetic neuron development and function

In neurons, many membrane proteins, synthesized in cell bodies, must be efficiently delivered to axons to influence neuronal connectivity, synaptic communication, and repair. Previously, we found that axonal targeting of TrkA neurotrophin receptors in sympathetic neurons occurs via an atypical transport mechanism called transcytosis, which relies on TrkA interactions with PTP1B, a protein tyrosine phosphatase. Here, we generated TrkAR685A mice, where TrkA receptor signaling is preserved, but its PTP1B-dependent transcytosis is disrupted to show that this mode of axonal transport is essential for sympathetic neuron development and autonomic function. TrkAR685A mice have decreased axonal TrkA levels invivo, loss of sympathetic neurons, and reduced innervation of targets. The neuron loss and diminished target innervation phenotypes are specifically restricted to the developmental period when sympathetic neurons are known to rely on the TrkA ligand, nerve growth factor, for trophic support. Postnatal TrkAR685A mice exhibit reduced pupil size and eyelid ptosis, indicative of sympathetic dysfunction. Furthermore, we also observed a significant loss of TrkA-expressing nociceptive neurons in the dorsal root ganglia during development in TrkAR685A mice, suggesting that transcytosis might be a general mechanism for axonal targeting of TrkA receptors. Together, these findings establish the necessity of transcytosis in supplying TrkA receptors to axons, specifically during development, and highlight the physiological relevance of this axon targeting mechanism in the nervous system.

A randomized phase 2 clinical trial of phentolamine mesylate eye drops in patients with severe night vision disturbances

PurposeDim light vision disturbances (DLD) comprise a wide range of symptoms affecting the quality of vision at low illumination including glare, halos, and starbursts. This exploratory study investigated 1.0% phentolamine mesylate ophthalmic solution (PMOS) as a treatment to improve vision and image quality for patients with DLD.MethodsIn this placebo-controlled, randomized, double-masked clinical trial, 24 adult patients with severe DLD were randomized in a 2:1 ratio to receive either one dose of PMOS or placebo. Subjects were eligible if they reported experiencing severe night vision difficulty that was not eliminated by distance spectacle correction and scored ≥0.3 log units below the normal range of contrast sensitivity assessed under mesopic conditions with glare at ≥2 spatial frequencies. Key efficacy outcomes were change from baseline in pupil diameter, contrast sensitivity, and visual acuity. Safety measures including intraocular pressure, conjunctival hyperemia, and systemic effects were also assessed.ResultsEight subjects were randomized to placebo (63% female; mean age 47 years) and 16 were randomized to PMOS (75% female; mean age 42 years). Mean (SD) pupil diameter of PMOS-treated subjects decreased significantly − 1.3 mm (0 to − 2.8 mm) with p < 0.0001. Mean contrast sensitivity with glare in PMOS-treated subjects improved significantly post-treatment at spatial frequencies 3, 6, 12, and 18 cycles per degree (p ≤ 0.03). PMOS also demonstrated improvements in the numbers of letters read for mesopic and photopic, high- and low-contrast visual acuity (LCVA). Importantly, a statistically greater proportion of PMOS-treated eyes registered mesopic LCVA 5 letter (69% vs. 31%, p = 0.029) and 10 letter (34% vs. 6%, p = 0.04) improvement, with a trend at 15 letters (19% vs. 0%, p = 0.16). PMOS was well tolerated with the only reported side effect being a mild increase in conjunctival hyperemia.ConclusionPMOS was well tolerated and effectively reduced pupil size with improvements in contrast sensitivity and visual acuity in adults with severe DLD. Future Phase 3 studies should be conducted to further evaluate its potential to treat DLD.Trial registrationThe trial registration number is NCT04004507 (02/07/2019). Retrospectively registered.

Own Race Eye-Gaze Bias for All Emotional Faces but Accuracy Bias Only for Sad Expressions.

Own race faces tend to be recognized more accurately than those of other less familiar races, however, findings to date have been inconclusive. The present study aimed to determine whether Chinese exhibit different recognition accuracy and eye gaze patterns for Asian (own-race) and White (other-race) facial expressions (neutral, happiness, sadness, anger, disgust, fear). A total of 89 healthy Chinese adults viewed Asian and White facial expressions while undergoing eye-tracking and were subsequently required to identify expressions and rate their intensity and effect on arousal. Results revealed that subjects recognized sad expressions in Asian faces better than in White ones. On the other hand, recognition accuracy was higher for White neutral, happy, fearful, and disgusted expressions although this may have been due to subjects more often misclassifying these Asian expressions as sadness. Moreover, subjects viewed the eyes of emotional expressions longer in Asian compared to White faces and the nose of sad ones, especially during the late phase of presentation, whereas pupil sizes, indicative of cognitive load and arousal, were smaller. Eye-gaze patterns were not, however, associated with recognition accuracy. Overall, findings demonstrate an own-race bias in Chinese for identifying sad expressions and more generally across emotional expressions in terms of viewing the eye region of emotional faces for longer and with reduced pupil size. Interestingly, subjects were significantly more likely to miss-identify Asian faces as sad resulting in an apparent other-race bias for recognizing neutral, happy, fearful, and disgusted expressions.

Transient effects of smoking on the eye

PurposeTo investigate the immediate short-term effects of smoking in habitual smokers, on the tear film, pupil size and accommodative ability of the human eye. MethodsHabitual smokers were tested within 5 min of smoking a cigarette. The tear film analysis was undertaken using tear break–up time (TBUT), tear lipid layer thickness and tears meniscus height (TMH) measurements. Three different ways of tear break–up time (TBUT) were used; using fluorescein; a non-invasive TBUT using tearscope; and a video captured method with a corneal topographer. Pupil size was measured objectively using the video capture on the corneal topographer. Accommodative ability was checked by performing a ‘push up test' to measure amplitudes of accommodation (AoA) and by measuring defocus curves. ResultsForty-five participants were enrolled (mean age 22.0 ± 4.4 years). TBUT was reduced after smoking a cigarette with all three assessment methods and this reduction was statistically significant (p < 0.001). A reduction in lipid layer thickness was seen after smoking a cigarette with both methods used and was statistically significant (p < 0.01). A significant reduction in pupil size (p < 0.01) and in AoA (p < 0.001) was observed after smoking a cigarette. The difference in TMH and defocus curves, before and after smoking, were not statistically significant (p > 0.05). ConclusionThe study shows that there is an immediate adverse effect of smoking on TBUT and AoA which seems to be very transient.

Maturation of Temporal Saccade Prediction from Childhood to Adulthood: Predictive Saccades, Reduced Pupil Size, and Blink Synchronization.

When presented with a periodic stimulus, humans spontaneously adjust their movements from reacting to predicting the timing of its arrival, but little is known about how this sensorimotor adaptation changes across development. To investigate this, we analyzed saccade behavior in 114 healthy humans (ages 6-24 years) performing the visual metronome task, who were instructed to move their eyes in time with a visual target that alternated between two known locations at a fixed rate, and we compared their behavior to performance in a random task, where target onsets were randomized across five interstimulus intervals (ISIs) and thus the timing of appearance was unknown. Saccades initiated before registration of the visual target, thus in anticipation of its appearance, were labeled predictive [saccade reaction time (SRT) < 90 ms] and saccades that were made in reaction to its appearance were labeled reactive (SRT > 90 ms). Eye-tracking behavior including saccadic metrics (e.g., peak velocity, amplitude), pupil size following saccade to target, and blink behavior all varied as a function of predicting or reacting to periodic targets. Compared with reactive saccades, predictive saccades had a lower peak velocity, a hypometric amplitude, smaller pupil size, and a reduced probability of blink occurrence before target appearance. The percentage of predictive and reactive saccades changed inversely from ages 8-16, at which they reached adult-levels of behavior. Differences in predictive saccades for fast and slow target rates are interpreted by differential maturation of cerebellar-thalamic-striatal pathways.SIGNIFICANCE STATEMENT From the first moments of life, humans are exposed to rhythm (i.e., mother's heartbeat in utero), but the timeline of brain development to promote the identification and anticipation of a rhythmic stimulus, known as temporal prediction, remains unknown. Here, we used saccade reaction time (SRT) in the visual metronome task to differentiate between temporally predictive and reactive responses to a target that alternated at a fixed rate in humans aged 6-24. Periods of age-related change varied little by target rate, with matured predictive performance evident by mid-adolescence for fast and slow rates. A strong correlation among saccade, pupil, and blink responses during target prediction provides evidence of oculomotor coordination and dampened noradrenergic neuronal activity when generating rhythmic motor responses.

RoWDI: rolling window detection of sleep intrusions in the awake brain using fMRI

Objective. Brief episodes of sleep can intrude into the awake human brain due to lack of sleep or fatigue—compromising the safety of critical daily tasks (i.e. driving). These intrusions can also introduce artefactual activity within functional magnetic resonance imaging (fMRI) experiments, prompting the need for an objective and effective method of removing them. Approach. We have developed a method to track sleep-like events in awake humans via rolling window detection of intrusions (RoWDI) of fMRI signal template. These events can then be used in voxel-wise event-related analysis of fMRI data. To test this approach, we generated a template of fMRI activity associated with transition to sleep via simultaneous fMRI and electroencephalogram (EEG) (N = 10). RoWDI was then used to identify sleep-like events in 20 individuals performing a cognitive task during fMRI after a night of partial sleep deprivation. This approach was further validated in an independent fMRI dataset (N = 56). Main results. Our method (RoWDI) was able to infer frequent sleep-like events during the cognitive task performed after sleep deprivation. The sleep-like events were associated with on average of 20% reduction in pupil size and prolonged response time. The blood-oxygen-level-dependent activity during the sleep-like events covered thalami-cortical regions, which although spatially distinct, co-existed with, task-related activity. These key findings were validated in the independent dataset. Significance. RoWDI can reliably detect spontaneous sleep-like events in the human brain. Thus, it may also be used as a tool to delineate and account for neural activity associated with wake-sleep transitions in both resting-state and task-related fMRI studies.

Hearing Aid Noise Reduction Lowers the Sustained Listening Effort During Continuous Speech in Noise-A Combined Pupillometry and EEG Study.

The investigation of auditory cognitive processes recently moved from strictly controlled, trial-based paradigms toward the presentation of continuous speech. This also allows the investigation of listening effort on larger time scales (i.e., sustained listening effort). Here, we investigated the modulation of sustained listening effort by a noise reduction algorithm as applied in hearing aids in a listening scenario with noisy continuous speech. The investigated directional noise reduction algorithm mainly suppresses noise from the background. We recorded the pupil size and the EEG in 22 participants with hearing loss who listened to audio news clips in the presence of background multi-talker babble noise. We estimated how noise reduction (off, on) and signal-to-noise ratio (SNR; +3 dB, +8 dB) affect pupil size and the power in the parietal EEG alpha band (i.e., parietal alpha power) as well as the behavioral performance. Our results show that noise reduction reduces pupil size, while there was no significant effect of the SNR. It is important to note that we found interactions of SNR and noise reduction, which suggested that noise reduction reduces pupil size predominantly under the lower SNR. Parietal alpha power showed a similar yet nonsignificant pattern, with increased power under easier conditions. In line with the participants' reports that one of the two presented talkers was more intelligible, we found a reduced pupil size, increased parietal alpha power, and better performance when people listened to the more intelligible talker. We show that the modulation of sustained listening effort (e.g., by hearing aid noise reduction) as indicated by pupil size and parietal alpha power can be studied under more ecologically valid conditions. Mainly concluded from pupil size, we demonstrate that hearing aid noise reduction lowers sustained listening effort. Our study approximates to real-world listening scenarios and evaluates the benefit of the signal processing as can be found in a modern hearing aid.

Effects and mechanisms of information saliency in enhancing value-based decision-making in younger and older adults

Aging attenuates frontostriatal network functioning, which could lead to deficits in value computation when decision-making involves uncertainty. Although it has been shown that visually enhancing information saliency of outcome probability can improve decision-making in old age, mechanisms of this effect are still unclear. In the present study, the saliency of outcome probability was increased using a color-coding scheme as a decision aid in a mixed lottery choice task, and spontaneous eye-blink rate and pupillary responses were assessed in younger and older adults. Older adults showed lower value sensitivity than younger adults; however, increasing information saliency benefitted choice behaviors in both age groups. Furthermore, the decision aid reduced pupil size during decision-making in both age groups, suggesting that enhancing information saliency decreases cognitive demands of value computation. Baseline value sensitivity was negatively correlated with benefit of enhancing information saliency only in older adults. As value representations in older decision makers are less distinctive at baseline, they may have required more environmental compensation than younger adults.

A Pilot Study of Automated Pupillometry in the Treatment of Opioid Use Disorder.

Introduction/Background:A rough, visual estimate of pupil size is used in grading the severity of opioid withdrawal. Few studies have examined the clinical utility of more precise automated pupillometry measurements.Methods:This prospective cohort study enrolled 27 patients receiving opioid agonist therapy (OAT) to treat cravings or withdrawal during an acute hospitalization. Six sets of automated pupillometry measurements were obtained at regular intervals before and after administration of OAT. Clinical Opiate Withdrawal Scale measurements were performed pre and post OAT. Primary outcomes included pupil size in dark and bright illumination (mm). Latency of the pupillary light response (s), constriction and dilation velocity (mm/s), and percent constriction (%) were secondary outcomes.Results:The mean predosing pupil size in dark and bright illumination was 4.33 ± 1.40 mm and 2.96 ± 0.79 mm, respectively. A significantly decreased mean pupil size was first detected at 15 minutes postdosing (4.01 ± 1.34 mm, P = 0.0115 for dark illumination; 2.71 ± 0.72 mm, P = 0.0003 for bright illumination) and this reduction in pupil size persisted at later postdosing timepoints. Those with Clinical Opiate Withdrawal Scale <5 after dosing had a greater decrease in dark pupil size (10.6% ± 13.2 vs 3.2% ± 3.2, P = 0.043). There was no significant change in the remaining pupil reactivity parameters.Conclusions:Automated pupillometry demonstrated a small but significant change in mean pupil size that occurred within 15 minutes of OAT dosing and was associated with low withdrawal scores. This pilot may inform future work to incorporate pupillometry measurement into OAT dosing assessments.

338-LB: ACh Esterase Is a Novel Regulator of Insulin Secretion in Human Islets

The neurotransmitter acetylcholine (ACh) plays a major role in regulating insulin secretion. While in several species parasympathetic innervation provides cholinergic input to beta cells, it is the glucagon secreting alpha cell the major source of ACh in human islets. It is still unclear, however, what is the contribution of cholinergic signaling to beta cell function in humans. Here we analyzed how ACh impacts human beta cell function and insulin secretion, using a combination of in vitro and in vivo approaches. To determine the effect of endogenous ACh in insulin secretion, we manipulated ACh esterase activity using different inhibitors such as pyridostigmine and galantamine. Inhibition of ACh esterase led to a significant increase in insulin secretion in isolated human islets in perifusion experiments. To assess the effect of endogenous ACh on human beta cell function in vivo, we transplanted human islets into the anterior chamber of immunocompromised Nude mice. ACh esterase activity was inhibited by local administration of the ACh esterase inhibitor pyridostigmine as eye drops. To control that the inhibitor was entering the anterior chamber of the eye and reaching the islets, we measured the effect it had on pupil size. 30 microM pyridostigmine induced approximately a 20-30% reduction in pupil size. Importantly, mice treated with 30 microM pyridostigmine showed decreased glucose excursion curves and slightly increased insulin levels 15 min after glucose injection. These results indicate that endogenously released ACh from human alpha cells increases insulin secretion from beta cells in vitro and in vivo. ACh esterase is potential novel target for the treatment of diabetes in humans. Disclosure A.M. Tamayo: None. A. Caicedo: None. Funding American Diabetes Association (1-17-ICTS-052 to A.C.)

Application of Purkinje images for pinhole pupilloplasty and relevance to chord length mu

To evaluate the results of pinhole pupilloplasty in cases with high astigmatism and higher-order aberrations (HOAs). Dr. Agarwal's Eye Hospital & Research Centre, Chennai. Case series. Pinhole pupilloplasty was performed based on the Purkinje 1 (P1) images formed from the light source of a Lumera surgical microscope; the images served as a reference marker for centration. A single-pass 4-throw technique was used to achieve a pinhole pupil. The preoperative and postoperative pupil diameter, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, simulated keratometry (K), and chord length mu (μ) were assessed, the latter using a Pentacam rotating Scheimpflug camera. Pinhole pupilloplasty was performed in 8 eyes (8 patients). There was a statistically significant reduction in the mean horizontal and vertical pupil diameters and in the mean pupil diameter from preoperatively to postoperatively (both P<.001). Although the improvement in UDVA was statistically significant (P<.001), the change in CDVA was not. The mean simulated K and mean chord length μ values were significantly lower postoperatively (P=.024 and P<.001, respectively). The reduction in pupil size was more apparent than the reduction in chord length μ. The correlation between the change in chord length μ and the change in pupil size was not significant (r=-0.067, P=.874). The pupil was well centered on the P1 images. No major adverse events or complications occurred postoperatively. Postoperative results showed a correlation between the improvement in visual acuity and the decrease in pupil size and chord length μ.

Increased sensitivity of the circadian system to light in delayed sleep-wake phase disorder.

This is the first study to demonstrate an altered circadian phase shifting response in a circadian rhythm sleep disorder. Patients with delayed sleep-wake phase disorder (DSWPD) demonstrate greater sensitivity of the circadian system to the phase-delaying effects of light. Increased circadian sensitivity to light is associated with later circadian timing within both control and DSWPD groups. DSWPD patients had a greater sustained pupil response after light exposure. Treatments for DSWPD should consider sensitivity of the circadian system to light as a potential underlying vulnerability, making patients susceptible to relapse. Patients with delayed sleep-wake phase disorder (DSWPD) exhibit delayed sleep-wake behaviour relative to desired bedtime, often leading to chronic sleep restriction and daytime dysfunction. The majority of DSWPD patients also display delayed circadian timing in the melatonin rhythm. Hypersensitivity of the circadian system to phase-delaying light is a plausible physiological basis for DSWPD vulnerability. We compared the phase shifting response to a 6.5h light exposure (∼150lux) between male patients with diagnosed DSWPD (n=10; aged 20.8±2.3years) and male healthy controls (n=11; aged 22.4±3.3years). Salivary dim light melatonin onset (DLMO) was measured under controlled conditions in dim light (<3lux) before and after light exposure. Correcting for the circadian time of the light exposure, DSWPD patients exhibited 31.5% greater phase delay shifts than healthy controls. In both groups, a later initial melatonin phase was associated with a greater magnitude phase shift, indicating that increased circadian sensitivity to light may be a factor that contributes to delayed phase, even in non-clinical groups. DSWPD patients also had reduced pupil size following the light exposure, and showed a trend towards increased melatonin suppression during light exposure. These findings indicate that, for patients with DSWPD, assessment of light sensitivity may be an important factor that can inform behavioural therapy, including minimization of exposure to phase-delaying night-time light.

Effects of brimonidine tartrate 0.1% ophthalmic solution on the pupil, refraction, and light reflex

This study aimed to assess changes in pupil size, uncorrected visual acuity, refraction, and the direct and consensual light reflexes after instillation of brimonidine 0.1% in healthy subjects. The investigation comprised 46 eyes of 23 healthy subjects with no eye diseases in whom brimonidine 0.1% was instilled in the right eye. Pupil size was measured quantitatively under photopic and scotopic conditions, uncorrected visual acuity, refraction, and direct and consensual light reflexes before and at 1, 6, and 24 h after instillation. We found No significant change was found in refraction or uncorrected visual acuity (P = 0.999 and P = 0.998, respectively). A significant reduction in pupil size was observed under scotopic conditions at 1 h and 6 h after instillation (P = 0.007 and P = 0.005, respectively). The rate of pupil contraction and constriction speed measured by light reflexes were significantly increased at 1 h and 6 h after instillation (P = 0.021 and P = 0.033, respectively). Brimonidine 0.1% induced a significant reduction in pupil size under scotopic conditions without a significant change in refraction or visual acuity due to suppression of the sympathetic nervous system.

Impact of large field angles on the requirements for deformable mirror in imaging satellites

For certain imaging satellite missions, a large aperture with wide field-of-view is needed. In order to achieve diffraction limited performance, the mirror surface Root Mean Square (RMS) error has to be less than 0.05 waves. In the case of visible light, it has to be less than 30 nm. This requirement is difficult to meet as the large aperture will need to be segmented in order to fit inside a launch vehicle shroud. To reduce this requirement and to compensate for the residual wavefront error, Micro-Electro-Mechanical System (MEMS) deformable mirrors can be considered in the aft optics of the optical system. MEMS deformable mirrors are affordable and consume low power, but are small in size. Due to the major reduction in pupil size for the deformable mirror, the effective field angle is magnified by the diameter ratio of the primary and deformable mirror. For wide field of view imaging, the required deformable mirror correction is field angle dependant, impacting the required parameters of a deformable mirror such as size, number of actuators, and actuator stroke. In this paper, a representative telescope and deformable mirror system model is developed and the deformable mirror correction is simulated to study the impact of the large field angles in correcting a wavefront error using a deformable mirror in the aft optics.

Age‐dependent prediction of visible differences in displayed images

AbstractA comprehensive computational model of the human visual system has been developed to predict just‐noticeable differences between a pair of stimuli. The stimuli are provided as high‐dynamic‐range, multichannel images, containing accurate spectral and photometric description of the scene. In this work, we extend such a model to determine the effect of age on the sensitivity of the visual system. The extensions are based on the existing models of disability glare, aging of the crystalline lens, and reduced pupil size with age (senile miosis). We confirm findings from other studies that those optical effects cannot fully explain the effect of aging, and we attribute the remaining drop of sensitivity to neural changes. The complete model, including an empirical neural component, can well explain the differences in contrast sensitivity between old and young observers.

Expectancy modulates pupil size during endogenous orienting of spatial attention

fMRI investigations in healthy humans have documented phasic changes in the level of activation of the right temporal-parietal junction (TPJ) during cued voluntary orienting of spatial attention. Cues that correctly predict the position of upcoming targets in the majority of trials, i.e., predictive cues, produce higher deactivation of the right TPJ as compared with non-predictive cues. Since the right TPJ is the recipient of noradrenergic (NE) innervation, it has been hypothesised that changes in the level of TPJ activity are matched with changes in the level of NE activity. Based on aforementioned fMRI findings, this might imply that orienting with predictive cues is matched with different levels of NE activity as compared with non-predictive cues. To test this hypothesis, we measured changes in pupil dilation, an indirect index of NE activity, during voluntary orienting of attention with highly predictive (80% validity) or non-predictive (50% validity) cues. In agreement with current interpretations of the tonic/phasic activity of the Locus Coeruleus-Norepinephrinic system (LC-NE), we found that the steady level of cue predictiveness that characterised both the predictive and non-predictive conditions caused, across consecutive blocks of trials, a progressive decrement in pupil dilation during the baseline-fixation period that anticipated the cue period. With predictive cues we observed increased pupil dilation as compared with non-predictive cues. In addition, the relative reduction in pupil size observed with non-predictive cues increased as a function of cue-duration. These results show that changes in the predictiveness of cues that guide voluntary orienting of spatial attention are matched with changes in pupil dilation and, putatively, with corresponding changes in LC-NE activity.

Effect of topical anti-glaucoma medications on late pupillary light reflex, as evaluated by pupillometry.

The late post-illumination pupillary response (PIPR 10-30s ) to blue light is reduced in glaucoma, suggesting that pupillometry can be used in clinical glaucoma evaluation. Since animal studies have indicated that common anti-glaucomatous agents affect the iris muscle, we investigated the short-term effect of the anti-glaucoma drugs on the pupillary light reflex and in particular on the PIPR10-30s. In this randomized, double-masked, crossover trial, pupillometry was performed before and after topical administration of latanoprost, dorzolamide, and timolol in 20 healthy subjects. Stimulus was blue (463 nm) and red light (633 nm) of 2 log (lux). Main outcome was the PIPR10-30s to blue light. Additionally, pupil size, maximal contraction, and the early post-illumination pupillary response (PIPR 0-10s ) to blue and red light were investigated. Pupil response variations between 8 a.m. and 2 p.m. were also assessed. Intraocular pressure (IOP) was measured before and 3.5 h after drug instillation. We found no drug effect on the blue light PIPR10-30s or any other blue light pupil parameters. During the control day, the only significant variation over time was observed for the red light PIPR0-10s (p = 0.02). Pupillary size decreased slightly with timolol (0.1 mm, p = 0.03) and dorzolamide (0.2 mm, p < 0.001), but not with latanoprost. Timolol also reduced the maximal contraction amplitude significantly during red light (p = 0.02). Intraocular pressure was significantly reduced by all three drugs after 3.5 h (p < 0.01), while it remained unchanged during the control day (p = 0.3). Anti-glaucoma medications did not interfere with the blue light elicited PIPR. Dorzolamide reduced pupil size, while timolol reduced both pupil size and maximal contraction to red light, but the effect was minute and not of clinical importance.