Intrasession repeatability and agreement of a new method to measure the foveal fixation axis.

Purpose: Ophthalmic lens adaptation, particularly with progressive addition lenses, requires accurate measurements of the patient nasopupillary distance (NPD) and interpupillary distance (IPD), which are usually collected using the pupil centre as a reference. However, differences between the pupil centre and visual or foveal axis could induce some subsidiary effects of correcting lenses. This study aimed to assess the intrasession repeatability of a new prototype (Ergofocus®; Lentitech, Barakaldo, Spain) that can measure the foveal fixation axis (FFA) distance and assess the agreement with the NPD measurements collected using a traditional method (frame ruler). Methods: The FFA at far and near distances was measured three consecutive times in 39 healthy volunteers to determine the intrasession repeatability according to the British Standards Institute and International Organization for Standardization. Additionally, the FFA and NPD (standard frame ruler) were measured in 71 healthy volunteers and compared using Bland-Altman analysis. Two blinded experienced practitioners conducted each FFA and NPD measurement. Results: The FFA measurements showed acceptable repeatability at far distances (right eye (RE): Sw = 1.16 ± 0.76 mm and coefficient of variation (CV) = 3.92 ± 2.51%; left eye (LE) Sw = 1.11 ± 0.79 mm and CV = 3.76 ± 2.51%) and at near distances (RE: Sw = 0.97 ± 0.85 mm and CV = 3.52 ± 3.02%; LE: Sw = 1.17 ± 0.96 mm and CV = 4.54 ± 3.72%). Additionally, agreement with the NPD showed large differences at far distances (RE: -2.15 ± 2.34, LoA = -6.73 to 2.43 mm (P < 0.001); LE: -0.61 ± 2.62, LoA = -5.75 to 4.53 mm (P = 0.052)) and near distances (RE: -3.08 ± 2.80, LoA -8.57 to 2.42 mm (P < 0.001); LE: -2.97 ± 3.97, LoA: -10.75 to 4.80 mm (P < 0.001)). Conclusions: FFA measurements showed clinically acceptable repeatability at both far and near distances. Agreement with the NPD measured using a standard frame ruler showed significant differences, suggesting that both measurements are not interchangeable in clinical practice to prescribe and center ophthalmic lenses. Further research is necessary to assess the impact of FFA measurement in ophthalmic lens prescriptions.

A novel Y-shaper and chopper for small pupil management in cataract surgery: The initial experience.

Small pupil is a well-known risk factor for causing cataract surgery complications such as vitreous loss, anterior capsular tear, increased inflammation, and an irregular pupil shape. Because all currently available pharmacological approaches of dilating the pupil before or during cataract surgery cannot guarantee the result, the surgeon sometimes resorts to the use of mechanical pupil-expanding devices. However, these devices can increase the overall surgical cost and operative time. Very frequently, a combination of the two is needed; thus, we present the Y-shaped chopper designed by the authors, which serves the purpose of managing the intra-operative miosis and allows simultaneous nuclear emulsification.

Task-Evoked Pupillary Response as a Potential Biomarker of Dementia and Mild Cognitive Impairment: A Scoping Review.

Pupil dilation functions as a proxy for cognitive effort and can be measured through automated pupillometry. The aim of this scoping review is to examine how individuals with cognitive impairment differ in task-evoked pupillary responses relative to cognitively healthy individuals. A systematic literature search across six databases was conducted to identify studies examining changes in pupillary responses evoked by cognitive tasks comparing patients with dementia to healthy controls. Eight articles met inclusion criteria and were included for review. Differences in task-evoked pupillary response between cognitively impaired and cognitively healthy participants were observed across studies. Pupil dilation is decreased in patients with Alzheimer's Disease compared to controls, with no difference observed in patients with mild cognitive impairment. A mild, non-significant trend towards reduced pupil dilation in patients with either Parkinson's Disease or Dementia with Lewy Bodies suggests a similar but less pronounced effect than in AD patients. Further research is required to examine the utility of task-evoked pupillary responses as a potential biomarker indexing cognitive decline in individuals transitioning to mild cognitive impairment and/or dementia.

Customization of spectacle frames for individuals with facial deformities by altering conventional spectacle frames - Phase I.

Purpose: Manufacturing a spectacle frame for a facially deformed individual is challenging because of facial asymmetry. One of the solutions is the customization of spectacle frames. Customization of spectacle frames for facially deformed individuals requires a better understanding of the facial anthropometry of deformed faces. This study aimed to analyze the facial anthropometry of deformed faces to understand the range of variability. The results of this study will be used to find customization methods in the future. Methods: We measured and analyzed the 12 facial parameters of individuals with facial deformities using the ImageJ software. Results: The data collected were normally distributed. Paired sample test revealed a statistically significant difference between innercanthus distances (right innercanthus distance [RICD] and left innercanthus distance [LICD]). Correlation analysis showed a positive difference between horizontal and vertical pupillary distance-innercanthus distance (PD-ICD) (0.68, 0.75, and 0.81) and pupillary distance-helix distance (PD-HD) (0.57, 0.68, and 0.59) relations. PD-ICD correlations are stronger compared to the PD-HD relation. Conclusion: Altering the frame center distance and the temple heights are the most important for asymmetric faces. Large population-based data are required to make concrete decisions to design a spectacle frame for asymmetric faces.

Is the Pupil Involved in Duane Syndrome? Static and Dynamic Pupillometry Characteristics.

Objectives: Duane syndrome (DS) is typically characterized by abduction and/or adduction deficiency accompanied by eyelid and ocular motility disturbances. Maldevelopment or absence of the sixth nerve has been shown to be the causative factor. The aim of the present study was to investigate static and dynamic pupillary characteristics in patients with DS and compare the results with those of healthy eyes. Materials and Methods: Patients with unilateral isolated DS and no history of ocular surgery were enrolled in the study. Healthy subjects with a best corrected visual acuity (BCVA) of 1.0 or higher were assigned to the control group. All subjects underwent complete ophthalmological examination and pupillometry measurements (MonPack One, Vision Monitor System, Metrovision, Perenchies, France) including static and dynamic pupil evaluation. Results: A total of 74 patients (22 with DS and 52 healthy subjects) were included in the study. The mean age of the DS patients and healthy subjects was 11.05±5.19 and 12.54±4.05 years, respectively (p=0.188). There was no difference in sex distribution (p=0.502). Mean BCVA differed significantly between eyes with DS and healthy eyes, and between healthy eyes and the fellow eyes of DS patients (p<0.05). No significant difference was found in any static or dynamic pupillometry parameters (p>0.05 for all). Conclusion: In the light of the results of the present study, the pupil seems to be not involved in DS. Larger studies including more patients with different types of DS in different age groups or comprising patients with non-isolated DS may reveal different findings.

Differentiating between Bayesian parameter learning and structure learning based on behavioural and pupil measures.

Within predictive processing two kinds of learning can be distinguished: parameter learning and structure learning. In Bayesian parameter learning, parameters under a specific generative model are continuously being updated in light of new evidence. However, this learning mechanism cannot explain how new parameters are added to a model. Structure learning, unlike parameter learning, makes structural changes to a generative model by altering its causal connections or adding or removing parameters. Whilst these two types of learning have recently been formally differentiated, they have not been empirically distinguished. The aim of this research was to empirically differentiate between parameter learning and structure learning on the basis of how they affect pupil dilation. Participants took part in a within-subject computer-based learning experiment with two phases. In the first phase, participants had to learn the relationship between cues and target stimuli. In the second phase, they had to learn a conditional change in this relationship. Our results show that the learning dynamics were indeed qualitatively different between the two experimental phases, but in the opposite direction as we originally expected. Participants were learning more gradually in the second phase compared to the first phase. This might imply that participants built multiple models from scratch in the first phase (structure learning) before settling on one of these models. In the second phase, participants possibly just needed to update the probability distribution over the model parameters (parameter learning).

External validation of the Glasgow Coma Scale-Pupils in patients with severe head injury. / Validación externa de la Escala de Coma de Glasgow con valoración pupilar en pacientes con traumatismo craneoencefálico grave.

OBJECTIVES: To compare the ability of the Glasgow Coma Scale (GCS) score, the GCS Pupils (GCS-P) score, and the Pupil Reactivity Score (PRS) to predict mortality in patients with severe head injury. MATERIAL AND METHODS: Retrospective analysis of all patients with severe head injury and initial GCS scores of 8 or lower on initial evaluation for whom records included pupil dilation information and clinical course after admission to intensive care units of participating hospitals. We assessed the ability of each of the 3 scores (GCS, GCS-P, and PRS) to predict mortality using discrimination analysis. Discrimination was estimated by calculating the areas under the receiver operating characteristic curves (AUC) and 95% CIs. RESULTS: A total of 1551 patients with severe head injury and pupil dilation records were studied. The mean age was 50 years, 1190 (76.7%) were males, and 592 (38.2%) died. No pupil dilation was observed in 905 patients (58.3%), 362 (23.3%) had unilateral mydriasis, and 284 (18.3%) had bilateral mydriasis. The GCS-P score was significantly better at predicting mortality, with an AUC of 0.77 (95% CI, 0.74-0.79), versus 0.69 (95% CI, 0.67-0.72) for the GCS, and 0.75 (95% CI, 0.72-0.77) for the PRS. As the GCS-P score decreased, mortality increased. CONCLUSION: The GCS-P was more useful than the GCS for predicting death after severe head injury.

OBJETIVO: Analizar la capacidad para predecir la mortalidad hospitalaria de la Escala de Coma de Glasgow con valoración pupilar (GCS-P) comparado con la Escala de Coma de Glasgow (GCS) y con la escala de reactividad pupilar (PRS) en pacientes con traumatismo craneoencefálico (TCE) grave. METODO: Análisis retrospectivo de cohortes de todos los pacientes con TCE, puntuación en la GCS # 8 en la atención inicial, datos de exploración pupilar inicial y del desenlace hospitalario ingresados en las unidades de cuidados intensivos participantes. Se determinó la capacidad predictiva de mortalidad de la GCS, PRS y la GCS-P mediante un análisis de discriminación. La discriminación se analizó empleando curvas operativas del receptor (COR), el área bajo la curva (ABC) y su intervalo de confianza del 95% (IC 95%). RESULTADOS: Se analizaron 1.551 pacientes con TCE grave y datos sobre exploración pupilar. La edad media fue de 50 años, 1.190 (76,7%) eran hombres, y hubo 592 (38,2%) defunciones. Hubo 905 (58,3%) pacientes sin alteraciones pupilares, 362 (23,3%) con midriasis unilateral y 284 (18,3%) pacientes con midriasis bilateral. El análisis del ABCCOR para predecir la mortalidad hospitalaria mostró de forma significativa una mejor capacidad predictiva del GCS-P con ABC = 0,77 (IC 95% 0,74-0,79) respecto al GCS con ABC = 0,69 (IC 95% 0,67-0,72). La reactividad pupilar mostró un ABC = 0,75 (IC 95% 0,72-0,77). Se observó un incremento de mortalidad con la disminución del GCS-P. CONCLUSIONES: La escala GCS-P presentó mejor rendimiento que la GCS para predecir mortalidad en el TCE grave.

Changes in pupil dilation and P300 amplitude indicate the possible involvement of the locus coeruleus-norepinephrine (LC-NE) system in psychological flow.

Psychological flow is a state of full task immersion. The present study was conducted to test the hypothesis that psychological flow is positively related to activity of the phasic locus coeruleus-norepinephrine (LC-NE) system, which supports decisions on whether to engage in or disengage from the current activity. Subjective flow was assessed among 36 participants who engaged in a gamified version of the n-back task with various difficulty levels (0, 1, 2, and 3 back). During the tasks, continuous pupil diameter and EEG were recorded. We found that psychological flow and two presumed indicators of the phasic LC-NE activity (pupil dilation and EEG P300 amplitude) fit inverted U-shapes with increasing subjective task difficulty. Moreover, a positive linear relationship between psychological flow and pupil dilation (not with P300) was found. In conclusion, this study indicates the involvement of the LC-NE system in the peak experience of flow.

Comparison of Ocular Wavefront Aberration Measurements Obtained Using Two Hartmann-Shack Wavefront Aberrometers.

OBJECTIVES: To assess agreement between measurements of ocular wavefront aberrations obtained using the Pentacam AXL Wave (Oculus Optikgeräte GmbH) (Aberrometer A) and KR-1W (Topcon Corp) (Aberrometer B), both of which are based on the Hartmann-Shack principle. METHODS: In this prospective case-control study, ocular wavefront aberrations measurements were obtained using both aberrometers in patients with keratoconus (KC) and control participants. Ocular wavefront aberrations were measured through the natural pupil without dilation using both devices in a dark room. For both aberrometers, accommodation was inhibited by automatically adding fogging. The individual Zernike coefficients from the second to fourth order were compared between the two aberrometers for a 4-mm pupil diameter. RESULTS: Twenty-six KC and 29 control eyes were assessed. Statistically significant correlations ( P <0.05) were observed for all Zernike coefficients, except for Z 4-2 in the control group. Bland-Altman analysis indicated good agreement between aberrometers and no statistically significant differences in the control group. However, in the KC group, patterns of proportional error were observed in vertical coma Z 3-1 (r=0.338, P =0.008), trefoil Z 4-4 (r=0.701, P =0.003), secondary astigmatism Z 4-2 (r=0.348, P =0.025), and spherical aberrations Z 40 (r=0.407, P =0.012). CONCLUSIONS: The Zernike coefficient values measured by the two aberrometers were well correlated in the control and KC groups. However, in eyes with KC, Aberrometer B tended to present greater values in several Zernike coefficients than Aberrometer A, suggesting that wavefront measurements obtained using the two aberrometers are not interchangeable in patients with KC.

FIAT: A Device for Objective, Optical Measures of Accommodation in Phakic and Pseudophakic Eyes.

Purpose: To present FIAT, a novel optical instrument and analysis package that is designed to elicit and optically record accommodation in human eyes. Methods: FIAT employs a Shack-Hartmann wavefront sensor and a retro-illumination pupil camera that records from a single eye at video rates. It is effective at eliciting accommodation by offering the subject a full-field binocular view of an alternating distant target and a near-eye display. FIAT analysis software computes wave aberrations for each video frame over full- or subpupil sizes and computes accommodative dynamics and accommodative range. Results: The system is validated by showing accurate refraction measurements in model eyes and human eyes with trial lenses. Robust accommodative responses are shown for young eyes, and a lack of accommodative response is shown for a known presbyopes. Accommodative stimulus-response curves from five phakic subjects over a range of ages show expected results. Results from two individuals with monofocal intraocular lenses are shown. Conclusions: FIAT is an effective instrument for making accurate, objective measures of accommodation in phakic and pseudophakic eyes. Translational Relevance: We present a device that can play an important role in the development and testing of accommodating intraocular lenses.

The Trade-Off Between Luminance and Color Contrast Assessed With Pupil Responses.

Purpose: A scene consisting of a white stimulus on a black background incorporates strong luminance contrast. When both stimulus and background receive different colors, luminance contrast decreases but color contrast increases. Here, we sought to characterize the pattern of stimulus salience across varying trade-offs of color and luminance contrasts by using the pupil light response. Methods: Three experiments were conducted with 17, 16, and 17 healthy adults. For all experiments, a flickering stimulus (2 Hz; alternating color to black) was presented superimposed on a background with a complementary color to the stimulus (i.e., opponency colors in human color perception: blue and yellow for Experiment 1, red and green for Experiment 2, and equiluminant red and green for Experiment 3). Background luminance varied between 0% and 45% to trade off luminance and color contrast with the stimulus. By comparing the locus of the optimal trade-off between color and luminance across different color axes, we explored the generality of the trade-off. Results: The strongest pupil responses were found when a substantial amount of color contrast was present (at the expense of luminance contrast). Pupil response amplitudes increased by 15% to 30% after the addition of color contrast. An optimal pupillary responsiveness was reached at a background luminance setting of 20% to 35% color contrast across several color axes. Conclusions: These findings suggest that a substantial component of pupil light responses incorporates color processing. More sensitive pupil responses and more salient stimulus designs can be achieved by adding subtle levels of color contrast between stimulus and background. Translational Relevance: More robust pupil responses will enhance tests of the visual field with pupil perimetry.

Effect of pupil dilation on biometric iris recognition systems for personal authentication.

Purpose: To study the effect of pupil dilation on a biometric iris recognition (BIR) system for personal authentication and identification. Methods: A prospective, non-randomized, single-center cohort study was conducted on patients who reported for a routine eye check-up from November 2017 to November 2019 (2 years). An iris scanning device "IRITECH-MK2120U" was used to initially enroll the undilated eyes. Baseline scans were taken after matching with the enrolled database. All eyes were topically dilated and matched again with the enrolled database. The Hamming distance (a measure of disagreement between two iris codes) and recognition status were recorded from the device output, and eyes were evaluated by slit-lamp ophthalmoscopy with special emphasis on pupil shape, size, and texture. Results: All 321 enrolled eyes matched after topical dilation. The pupil size had a significant effect on Hamming distance with a P value <0.05. There were no false matches. A correct recognition rate of 100% was obtained after dilation. No loss of iris texture or pupil shape was observed after dilation. Conclusion: A BIR system is a reliable method for identification and personal authentication after pupil dilation. Topically dilated pupils are not a cause for non-recognition of iris scans.

The effect of intrinsically photosensitive retinal ganglion cell (ipRGC) stimulation on axial length changes to imposed optical defocus in young adults

Purpose: The intrinsically photosensitive retinal ganglion cells (ipRGCs) regulate pupil size and circadian rhythms. Stimulation of the ipRGCs using short-wavelength blue light causes a sustained pupil constriction known as the post-illumination pupil response (PIPR). Here we examined the effects of ipRGC stimulation on axial length changes to imposed optical defocus in young adults.Materials and methodsNearly emmetropic young participants were given either myopic (+3 D, n = 16) or hyperopic (-3 D, n = 17) defocus in their right eye for 2 h. Before and after defocus, a series of axial length measurements for up to 180 s were performed in the right eye using the IOL Master following exposure to 5 s red (625 nm, 3.74 × 1014 photons/cm2/s) and blue (470 nm, 3.29 × 1014 photons/cm2/s) stimuli. The pupil measurements were collected from the left eye to track the ipRGC activity. The 6 s and 30 s PIPR, early and late area under the curve (AUC), and time to return to baseline were calculated.ResultsThe PIPR with blue light was significantly stronger after 2 h of hyperopic defocus as indicated by a lower 6 and 30 s PIPR and a larger early and late AUC (all p<0.05). Short-wavelength ipRGC stimulation also significantly exaggerated the ocular response to hyperopic defocus, causing a significantly greater increase in axial length than that resulting from the hyperopic defocus alone (p = 0.017). Neither wavelength had any effect on axial length with myopic defocus.ConclusionsThese findings suggest an interaction between myopiagenic hyperopic defocus and ipRGC signaling. (AU)

Short bursts of transcutaneous auricular vagus nerve stimulation enhance evoked pupil dilation as a function of stimulation parameters.

Transcutaneous auricular vagus nerve stimulation (taVNS) is a neurostimulatory technique hypothesised to enhance central noradrenaline. Currently, there is scarce evidence in support of a noradrenergic mechanism of taVNS and limited knowledge on its stimulation parameters (i.e., intensity and pulse width). Therefore, the present study aimed to test whether taVNS enhances pupil dilation, a noradrenergic biomarker, as a function of stimulation parameters. Forty-nine participants received sham (i.e., left ear earlobe) and taVNS (i.e., left ear cymba concha) stimulation in two separate sessions, in a counterbalanced order. We administered short bursts (5s) of seven stimulation settings varying as a function of pulse width and intensity and measured pupil size in parallel. Each stimulation setting was administered sixteen times in separate blocks. We expected short bursts of stimulation to elicit phasic noradrenergic activity as indexed by event-related pupil dilation and event-related temporal derivative. We hypothesised higher stimulation settings, quantified as the total charge per pulse (pulse width x intensity), to drive greater event-related pupil dilation and temporal derivative in the taVNS compared to sham condition. Specifically, we expected stimulation settings in the taVNS condition to be associated with a linear increase in event-related pupil dilation and temporal derivative. We found stimulation settings to linearly increase both pupil measures. In line with our hypothesis, the observed dose-dependent effect was stronger in the taVNS condition. We also found taVNS to elicit more intense and unpleasant sensations than sham stimulation. These results support the hypothesis of a noradrenergic mechanism of taVNS. However, future studies should disentangle whether stimulation elicited sensations mediate the effect of taVNS on evoked pupil dilation.

Recommendation of using both initial pupil size and constriction latency in pupillary light reflex as objective indicators reflecting subacute pain-related mental fatigue.

A previous study examining clinical subacute pain models under different methodological conditions showed that pain-induced mental fatigue can be associated with decreased initial pupil size (INIT)/shortened constriction latency (LAT) in the pupillary light reflex (PLR). We aimed to investigate the potential of INIT/LAT as objective indicators reflecting mental fatigue under the same methodological conditions. We recruited 118 patients planning to undergo three types of representative otolaryngological head and neck surgery procedures. We used the numerical rating scale (NRS) to assess subjective pain intensity and two mental fatigue-related mood categories of the Profile of Mood States, as well as INIT and LAT measurements (1) in the afternoon one day before surgery (pre1-surgery), (2) in the morning of the day of surgery (pre2-surgery), and (3) in the morning of the day following surgery (post-surgery). We assessed time point-dependent changes using one- or two-way analysis of variance, as well as responses of PLR parameters to mental fatigue using linear mixed-effects models (LMMs). As a result, NRS scores, the two mood categories, as well as LAT and INIT, showed significant time point-dependent changes. In post-hoc analyses, only INIT showed significant changes between the two pre-surgery time points. Thus, INIT values fluctuated even under pain-free conditions due to differences in the time of the day. LMMs demonstrated decreased INIT/shortened LAT related to mental fatigue. All surgical groups showed similar associations between mental fatigue and INIT/LAT findings. As each parameter has advantages and disadvantages, it is recommended to use both INIT and LAT as the indicators.

Evaluation of pupil diameter for pain assessment in interventional headache management.

OBJECTIVES: Pain is a subjective experience. Besides, sensory, affective and behavioral responses, and autonomic response are part of pain response to noxious stimuli. Evaluation of pupil diameter by pupillometry has been used as an alternative method for pain assessment. In algologic procedures like interventional headache management have not been addressed in the literature. Herein, we investigated changes in pupil diameter during interventional headache management as an objective method for pain assessment. METHODS: Demographic data of the patients were collected before the bilateral major occipital nerve blockage (MONB) procedure. Numeric rating score (NRS) and pupil diameter measurements by pupillometer were recorded before MONB. Standard MONB procedure was applied to all patients. Pain assessment and pupillary diameter measurements were obtained after nerve blockage. RESULTS: Twenty-eight patients were included in this study. Mean age was 41.03+-12.63 years. There is no difference between the hemodynamic parameters before and after the procedure. Post-procedure NRS and pupil diameter values were significantly lower than pre-procedure values. There was a positive correlation between changes in NRS scores and changes in the right and left pupil diameters. CONCLUSION: There was a significant correlation between NRS score and pupil diameter in patients who underwent MONB. Monitoring of pupil diameter can be used for pain assessment during headache treatment. Evaluation of pupil diameter is a new approach in pain palliation. Future research is needed to study the effect of other parameters, that is, gender, age, origin of pain, acute, and chronic pain on pupil diameter and to evaluate its application in different algological procedures.

Reliability and agreement of apparent chord mu measurements between static and dynamic evaluations.

PURPOSE: To assess the repeatability and agreement of Cartesian coordinates and the length of apparent chord mu and pupil diameter measurements during static (Galilei G4) and dynamic (Topolyzer Vario) evaluations. SETTING: IOBA-Eye Institute, Valladolid, Spain. DESIGN: Case series. METHODS: 3 consecutive measurements per scenario (Galilei G4 and Topolyzer Vario under low mesopic and photopic conditions) were performed by the same clinician. The intrasession repeatability was assessed using the within-subject SD (Sw), the precision, the coefficient of variation, and the intraclass correlation coefficient (ICC). The agreement was analyzed using repeated-measures analysis of variance and the Bland-Altman method. RESULTS: Thirty-seven healthy participants were recruited. The Sw values for chord mu parameters and pupil diameter ranged from 0.01 to 0.03 and 0.08 to 0.21, respectively. The ICC was ≥0.89 for all parameters. Galilei G4 and Topolyzer Vario under low mesopic and photopic conditions provided significantly different measures of apparent chord mu length (0.23 ± 0.11 mm, 0.30 ± 0.10 mm, and 0.25 ± 0.11 mm, respectively, P ≤ .02), X-coordinate (-0.18 ± 0.12 mm, -0.27 ± 0.11 mm, and -0.21 ± 0.12 mm, respectively, P < .001), and pupil diameter (3.38 ± 0.50 mm, 6.29 ± 0.60 mm, and 3.04 ± 0.41 mm, respectively, P < .001). Y-coordinate values obtained by Galilei G4 and Topolyzer Vario under low mesopic conditions were significantly different (0.06 ± 0.13 mm vs 0.03 ± 0.11 mm, respectively, P = .02), in contrast to Galilei G4 and Topolyzer Vario under photopic conditions (0.05 ± 0.13 mm, P = .82) and both illumination conditions of Topolyzer Vario (P ≥ .23). CONCLUSIONS: Galilei G4 and Topolyzer Vario provide consistent measurements of apparent chord mu Cartesian coordinates and length, as well as pupil diameter; however, the measurements are not interchangeable. Ophthalmic surgeons should consider these findings when planning customized intraocular lens implantation and refractive surgery procedures.

Relating Pupil Diameter and Blinking to Cortical Activity and Hemodynamics across Arousal States.

Arousal state affects neural activity and vascular dynamics in the cortex, with sleep associated with large changes in the local field potential and increases in cortical blood flow. We investigated the relationship between pupil diameter and blink rate with neural activity and blood volume in the somatosensory cortex in male and female unanesthetized, head-fixed mice. We monitored these variables while the mice were awake, during periods of rapid eye movement (REM), and non-rapid eye movement (NREM) sleep. Pupil diameter was smaller during sleep than in the awake state. Changes in pupil diameter were coherent with both gamma-band power and blood volume in the somatosensory cortex, but the strength and sign of this relationship varied with arousal state. We observed a strong negative correlation between pupil diameter and both gamma-band power and blood volume during periods of awake rest and NREM sleep, although the correlations between pupil diameter and these signals became positive during periods of alertness, active whisking, and REM. Blinking was associated with increases in arousal and decreases in blood volume when the mouse was asleep. Bilateral coherence in gamma-band power and in blood volume dropped following awake blinking, indicating a reset of neural and vascular activity. Using only eye metrics (pupil diameter and eye motion), we could determine the arousal state of the mouse ('Awake,' 'NREM,' 'REM') with >90% accuracy with a 5 s resolution. There is a strong relationship between pupil diameter and hemodynamics signals in mice, reflecting the pronounced effects of arousal on cerebrovascular dynamics.SIGNIFICANCE STATEMENT Determining arousal state is a critical component of any neuroscience experiment. Pupil diameter and blinking are influenced by arousal state, as are hemodynamics signals in the cortex. We investigated the relationship between cortical hemodynamics and pupil diameter and found that pupil diameter was strongly related to the blood volume in the cortex. Mice were more likely to be awake after blinking than before, and blinking resets neural activity. Pupil diameter and eye motion can be used as a reliable, noninvasive indicator of arousal state. As mice transition from wake to sleep and back again over a timescale of seconds, monitoring pupil diameter and eye motion permits the noninvasive detection of sleep events during behavioral or resting-state experiments.