Looking into your eyes: observed pupil size influences approach-avoidance responses

Our eyes convey information about a person. The pupils may provide information regarding our emotional states when presented along with different emotional expressions. We examined the effects of pupil size and vergence on inferring other people’s characteristics in neutral expression eyes. Pupil sizes were manipulated by overlaying black disks onto the pupils of the original eye images. The disk area was then changed to create small, medium, and large pupils. Vergence was simulated by shifting the medium-sized disks nasally in one eye. Pupil sizes were exaggerated for Experiment 1 and followed values from the literature for Experiment 2. The first Purkinje image from the eye photos in Experiment 2 was kept to preserve image realism. The characteristics measured were sex, age, attractiveness, trustworthiness, intelligence, valence, and arousal. Participants completed one of two online experiments and rated eight eye pictures with differently sized pupils and with vergence eyes. Both experiments were identical except for the stimuli designs. Results from Experiment 1 revealed rating differences between pupil sizes for all characteristics except sex, age, and arousal. Specifically, eyes with extremely small pupil sizes and artificial vergence received the lowest ratings compared to medium and large pupil sizes. Results from Experiment 2 only indicated weak effects of pupil size and vergence, particularly for intelligence ratings. We conclude that the pupils can influence how characteristics of another person are perceived and may be regarded as important social signals in subconscious social interaction processes. However, the effects may be rather small for neutral expressions.

Users can “voluntarily” control the size of their pupil by switching focus from a far target A (large pupil size) to a near target B (small pupil size), according to the pupillary accommodative response (PAR). Pupil size is governed by smooth muscles and has been suggested as communication pathway for patients affected by paralysis of skeletal muscles, such as in amyotrophic lateral sclerosis (ALS). We here present a video game that relies on PAR: a 2d side-scroller game where the user, by varying pupil size, controls the height at which a spaceship is moving aiming at colliding with bubbles to burst them and score points. The height at which the spaceship flies inversely depends on pupil area. The game is implemented on a Raspberry Pi board equipped with a IR camera and may record the time course of pupil size during the game, for off-line analysis. This application is intended as a tool to train and familiarize with the control of pupil size for alternative augmentative communication.

Background: Pseudoexfoliation (PXF) is a common age-related brillopathy characterized by the accumulation of extracellular material in ocular tissues. It is associated with small pupil size and zonular weakness, complicating cataract surgery. Objective: To assess pupil size and the effect of mydriatics in patients with pseudoexfoliation syndrome. Methods: A cross-sectional study conducted over 5 months at Santhiram Medical College, Nandyal. Adult patients with PXF underwent pupillary diameter measurement before and after administration of mydriatic drops. Results: 40% of patients had a small pupil pre-dilatation; post-dilatation, 84% still had pupils ≤6 mm. No signicant association between pupil size and age or sex was found. Conclusion: Small pupil in PXF patients poses challenges for cataract surgery. Early recognition and proper preoperative planning can reduce intraoperative complications and improve surgical outcomes.

When viewing pupil sizes change, our own pupil sizes change, a phenomenon known as pupillary contagion. This involuntary response is reliable between humans but can be affected by familiarity and empathy. We investigated whether the pupillary contagion response occurs for humans viewing familiar species—cats and dogs—and whether it is modulated by preferences for particular species. Pupil sizes were measured while viewing cat, dog and human images with small, medium and large pupils. Trait empathy, cat and dog affiliation and experience were subsequently measured. There was an image pupil size effect, but this did not vary by species. There was greater pupil size change to cats and dogs than to humans, but this might have been due to the varying size and appearance of the cats and dogs. Greater dog affiliation was also associated with smaller overall pupil size change to dogs and larger change to humans, but this did not interact with image pupil size. Dog affiliation might be associated with less arousal to dog images. In sum, pupillary contagion responses indicate a spontaneous transfer of information about internal states and the findings suggest that humans are sensitive to this across species, regardless of individual preference.

When attention wanders: Pupillometric signatures of fluctuations in external attention

Small-pupil versus multifocal strategies for expanding depth of focus of presbyopic eyes

Epipolis laser in keratomileusis (Epi-LASIK) and laser in situ keratomileusis (LASIK) are two main surgical techniques for myopia in refractive surgery at present. However, the visual outcome and optical quality after the two procedures are not clear. We conducted the current prospective study to compare ocular higher-order aberrations and evaluate optical quality after Epi-LASIK and LASIK. Sixty-two eyes were included. Thirty-two eyes were treated using Epi-LASIK and thirty eyes using LASIK. Best-corrected visual acuity, uncorrected visual acuity, manifest refraction, and wavefront aberrations were measured and analyzed preoperatively and 4-6months postoperatively. Wavefront aberrations were measured by Wavescan (VISX, Santa Clara, CA, USA) using a Hartmann-Shack sensor. The mean changes in RMS for the 5th order (S(5)) were 0.022 ± 0.009µm and 0.050 ± 0.010µm, which was significantly smaller in the Epi-LASIK group than in the LASIK group for a 6-mm pupil (P = 0.048, analysis of covariance). The mean changes in C (5) (-1) and C (5) (5) were significantly smaller in the Epi-LASIK group than in the LASIK group at both 3-mm and 6-mm pupil sizes (P = 0.027, 0.045 and 0.024, 0.027, analysis of covariance). Also, the changes in the contribution of coma-like and spherical-like aberration at 6-mm pupil size were statistically significantly different after both procedures (P = 0.000, randomized block design analysis of covariance). Both Epi-LASIK and LASIK show their own characteristics in increased higher-order aberration at smaller and larger pupil sizes, and may create different effects on optical quality for photopic (smaller pupil) and scotopic conditions (larger pupil). We speculate that the visual performance in the Epi-LASIK group may be better than in the LASIK group for the larger pupil size.

OBJECTIVES:In critically ill patients with neurologic disease, pupil examination abnormalities can signify evolving intracranial pathology. Analgesic and sedative medications (analgosedatives) target pupillary pathways, but it remains unknown how analgosedatives alter pupil findings in the clinical care setting. We assessed dexmedetomidine and other analgosedative associations with pupil reactivity and size in a heterogeneous cohort of critically ill patients with acute intracranial pathology.DESIGN:Retrospective cohort study.SETTING:Two neurologic ICUs between 2016 and 2018.PATIENTS:Critically ill adult patients with pupil measurements within 60 minutes of analgosedative administration. Patients with a history of intrinsic retinal pathology, extracranial injury, inaccessible brain imaging, or no Glasgow Coma Scale (GCS) data were excluded.INTERVENTIONS:None.MEASUREMENTS AND MAIN RESULTS:We used mixed-effects linear regression accounting for intrapatient correlations and adjusting for sex, age, GCS score, radiographic mass effect, medication confounders, and ambient light. We tested the association between an initiation or increased IV infusion of dexmedetomidine and pupil reactivity (Neurologic Pupil Index [NPi]) and resting pupil size (mm) obtained using NeurOptics NPi—200 (NeurOptics, Irvine, CA) pupillometer. Of our 221 patients with 9,897 pupil observations (median age, 60 [interquartile range, 50–68]; 59% male), 37 patients (166 pupil observations) were exposed to dexmedetomidine. Dexmedetomidine was associated with higher average NPi (β = 0.18 per 1 unit increase in rank-normalized NPi ± 0.04; p < 0.001) and smaller pupil size (β = –0.25 ± 0.05; p < 0.001). Exploratory analyses revealed that acetaminophen was associated with higher average NPi (β = 0.04 ± 0.02; p = 0.02) and that most IV infusion analgosedatives including propofol, fentanyl, and midazolam were associated with smaller pupil size.CONCLUSIONS:Dexmedetomidine is associated with higher pupil reactivity (high NPi) and smaller pupil size in a cohort of critically ill patients with neurologic injury. Familiarity with expected pupil changes following analgosedative administration is important for accurate interpretation of pupil examination findings, facilitating optimal management of patients with acute intracranial pathology.

目的 分析LASIK手术对高阶像差的影响,分析LASIK术前近视屈光度与LASIK术后眼的高阶像差的关系.方法采用WASCA波前像差仪测量150眼LASIK术前及术后1月及3月瞳孔直径分别为小瞳孔(3 mm)及大瞳孔(6.25mm)时的总高阶像差的均方根及第三和第四阶像差的Zernike系数,并计算出球差、慧差、第三及第四阶像差的均方根.对结果进行方差分析和直线相关分析.结果 LASIK术后,大瞳孔直径和小瞳孔直径下高阶像差均明显增高.无论瞳孔大小,术后3月较1月时高阶像差均轻微下降.大瞳孔直径下,光区直径为6.25mm时,术后球差、第四阶像差和总高阶像差与术前屈光度存在正相关.结论 LASIK术后,高阶像差明显增高,尤以球差最明显.术前屈光度越高,手术所导致的高阶像差也越大,屈光度过高的近视眼不宜采用波前像差引导的个体化屈光手术。

It is well established that pupil activity indexes cognitive processing. For instance, research has consistently demonstrated that the pupil reacts to working memory span task performance. However, little is known about pupil reaction to cognitive processing in Alzheimer's Disease (AD). We thus investigated whether span tasks can modulate pupil size in patients with AD. We invited 24 patients with AD and 24 healthy older adults to perform backward and forward spans, as well as to count aloud in a control condition, while their pupil activity was recorded with eye tracking glasses. In patients with AD, analysis demonstrated larger pupil size during backward spans (M = 2.12, SD = .39) than during forward spans (M = 1.98, SD = .36) [t(23) = 3.22, p = .004], larger pupil size during forward spans than during counting (M = 1.67, SD = .33) [t(23) = 4.75, p < .001], as well as larger pupil size during backward spans than during counting [t(23) = 10.60, p < .001]. In control participants, analysis demonstrated larger pupil size during backward spans (M = 3.36, SD = .49) than during forward spans (M = 2.85, SD = .68) [t(23) = 5.82, p < .001], larger pupil size during forward spans than during counting (M = 2.09, SD = .62) [t(23) = 5.42, < .001], as well as larger pupil size during backward spans than during counting [t(23) = 9.70, p < .001]. Results also demonstrated a significant interaction effect between groups and conditions [F(2,92) = 16.63, p < .001]; in other words, patients with AD have shown fewer variations on the pupil size across the conditions compared to the control participants. The larger pupil size during backward spans, compared with forward spans or counting, can be attributed to the high cognitive load of backward spans. The modulation of pupil size, as observed across backward/forward spans and counting, can possibly be attributed to sympathetic/adrenergic and parasympathetic/cholinergic activities. Our study demonstrates the value of pupillometry as a potential biomarker of cognitive processing in AD.

Perceived time often diverges from physical time. This discrepancy is important given the crucial role of time perception in numerous cognitive processes. A critical question concerning the non-veridicality of timing is whether and how different physical attributes (e.g., size, speed, and numerosity) influence perceived duration. The present study deals specifically with how perceived time depends on stimulus brightness, both of a to-be-timed stimulus and the background on which this stimulus is presented. The results of two experiments show that increased brightness lengthens perceived duration, and, surprisingly, that this is the case both for the stimulus and the background. The finding that stimulus brightness affects time perception is a much needed replication of classic studies; however, the finding that background brightness similarly affects time perception is novel, and suggests that time perception may be biased by low-level visual perception. Additionally, we tested the hypothesis that large pupils (as a result of spontaneous pupil-size fluctuations) are associated with longer perceived durations. This hypothesis was based on the common assumption that arousal affects both pupil size and time perception; however, in contrast to this hypothesis, results show that pupil size has no relation to perceived time. Taken together, our study suggests that time perception is strongly affected by low-level visual input (brightness) but not-or hardly-by pupil-linked arousal.

BackgroundQuantitative pupillometry is part of multimodal neuroprognostication of comatose patients after out-of-hospital cardiac arrest (OHCA). However, the reproducibility, repeatability, and reliability of quantitative pupillometry in this setting have not been investigated.MethodsIn a prospective blinded validation study, we compared manual and quantitative measurements of pupil size. Observer and device variability for all available parameters are expressed as mean difference (bias), limits of agreement (LoA), and reliability expressed as intraclass correlation coefficients (ICC) with a 95% confidence interval.ResultsFifty-six unique quadrupled sets of measurement derived from 14 sedated and comatose patients (mean age 70±12 years) were included.For manually measured pupil size, inter-observer bias was -0.14±0.44 mm, LoA of -1.00 to 0.71 mm, and ICC at 0.92 (0.86–0.95). For quantitative pupillometry, we found bias at 0.03±0.17 mm, LoA of -0.31 to 0.36 mm and ICCs at 0.99. Quantitative pupillometry also yielded lower bias and LoA and higher ICC for intra-observer and inter-device measurements.Correlation between manual and automated pupillometry was better in larger pupils, and quantitative pupillometry had less variability and higher ICC, when assessing small pupils. Further, observers failed to detect 26% of the quantitatively estimated abnormal reactivity with manual assessment.We found ICC >0.91 for all quantitative pupillary response parameters (except for latency with ICC 0.81–0.91).ConclusionAutomated quantitative pupillometry has excellent reliability and twice the reproducibility and repeatability than manual pupillometry. This study further presents novel estimates of variability for all quantitative pupillary response parameters with excellent reliability.

Quantitative pupillometry is part of multimodal neuroprognostication of comatose patients after out-of-hospital cardiac arrest (OHCA). However, the reproducibility, repeatability, and reliability of quantitative pupillometry in this setting have not been investigated. In a prospective blinded validation study, we compared manual and quantitative measurements of pupil size. Observer and device variability for all available parameters are expressed as mean difference (bias), limits of agreement (LoA), and reliability expressed as intraclass correlation coefficients (ICC) with a 95% confidence interval. Fifty-six unique quadrupled sets of measurement derived from 14 sedated and comatose patients (mean age 70±12 years) were included. For manually measured pupil size, inter-observer bias was -0.14±0.44 mm, LoA of -1.00 to 0.71 mm, and ICC at 0.92 (0.86-0.95). For quantitative pupillometry, we found bias at 0.03±0.17 mm, LoA of -0.31 to 0.36 mm and ICCs at 0.99. Quantitative pupillometry also yielded lower bias and LoA and higher ICC for intra-observer and inter-device measurements. Correlation between manual and automated pupillometry was better in larger pupils, and quantitative pupillometry had less variability and higher ICC, when assessing small pupils. Further, observers failed to detect 26% of the quantitatively estimated abnormal reactivity with manual assessment. We found ICC >0.91 for all quantitative pupillary response parameters (except for latency with ICC 0.81-0.91). Automated quantitative pupillometry has excellent reliability and twice the reproducibility and repeatability than manual pupillometry. This study further presents novel estimates of variability for all quantitative pupillary response parameters with excellent reliability.

Approximately 10% of the lowercase text on nonprescription drug labels is smaller than the 1 mm required by the Food and Drug Administration. The small size, combined with the progressive decline in accommodative amplitude and gain, poses a reading challenge for middle-aged emerging presbyopes. The purpose of this study was to evaluate the impact of progressing presbyopia and near adds on the ability of middle-aged patients to read small text routinely encountered on product labels. Geometrical optics was used to determine the impact of changing viewing distance, accommodation, and pupil size on retinal blur size. We photographed 261 consumer product labels in grocery, personal care, and nonprescription (over-the-counter) drug categories and used character recognition software to identify and size 255,298 printed letters. We computed the impact of viewing distance on the ratio of blur to letter detail and used published blur ratios of ≤4 and ≤2 to identify the conditions that allowed for letter recognition and proficient reading, respectively. Median/mode lowercase letter heights (in millimeters) were 1.39/1.16, 1.29/1.15, and 1.18/1.01, respectively, for groceries, personal care, and over-the-counter drug categories. Despite the increased angular subtense of approaching letters, blur ratios generally increased with reduced viewing distance because of increased defocus. Increased viewing distance decreased blur, but small (e.g., 1 mm) letters became too small to read proficiently (angular size <10 arcminutes) for distances beyond 37 cm. With larger pupils, blur ratios were too large to support proficient reading when accommodative amplitude dropped to ≤3 diopters. An add power sufficient to bring the far point closer than 37 cm was required to proficiently read small text. Product labels, especially nonprescription drug packages, typically use fonts that are too small to be read proficiently by unaided emmetropes with emerging presbyopia. This problem can be ameliorated by correction of presbyopia at an earlier age and with higher add powers.

Presbyopia is a ubiquitous age-related condition characterized by reduced near focusing ability due to lenticular stiffening. Pharmacologic agents such as pilocarpine have re-emerged as a less-invasive treatment option by inducing miosis and thereby enhancing depth of focus. However, the optimal pharmacologically induced pupil size that balances improved near vision with sufficient retinal illuminance remains undetermined. In this work, we present for the first time a direct integration of advanced theoretical modeling with a systematic synthesis of clinical trial outcomes to define the optimal target pupil size for pharmacologic presbyopia correction. We modeled visual performance using the Visual Strehl Ratio of the Optical Transfer Function (VSOTF) and convolved images of optotypes across a range of pupil diameters from 1.5 mm to 3.5 mm. This combined optical–clinical approach allowed us to quantitatively compare modeled image quality and depth of focus predictions with real-world clinical efficacy data from pilocarpine-based interventions. Simulations showed that smaller pupil sizes (1.5–2.5 mm) significantly extended depth of focus compared to standard multifocal optics while maintaining image quality within acceptable limits. These findings align with clinical trials of pilocarpine formulations, which commonly achieve post-treatment pupil diameters in the 2.0–2.5 mm range and are associated with clinically meaningful gains in near vision. Our analysis uniquely demonstrates that these clinically achieved pupil sizes closely match the theoretically optimal 2.0–3.0 mm range identified in our modeling, strengthening the evidence base for drug design and patient selection. These results reinforce the role of pharmacologically controlled pupil size as a central target in presbyopia management. By explicitly linking predictive optical modeling with aggregated clinical outcomes, we introduce a novel framework to guide future pharmacologic development strategies and refine clinical counseling in the emerging era of presbyopia therapeutics.