Increase In Pupil Diameter Research Articles

Disrupted neural activity patterns to novelty and effort in young adult APOE-e4 carriers performing a subsequent memory task.

IntroductionThe APOE e4 allele has been linked to poorer cognitive aging and enhanced dementia risk. Previous imaging studies have used subsequent memory paradigms to probe hippocampal function in e4 carriers across the age range, and evidence suggests a pattern of hippocampal overactivation in young adult e4 carriers.MethodsIn this study, we employed a word‐based subsequent memory task under fMRI; pupillometry data were also acquired as an index of cognitive effort. Participants (26 non‐e4 carriers and 28 e4 carriers) performed an incidental encoding task (presented as word categorization), followed by a surprise old/new recognition task after a 40 minute delay.ResultsIn e4 carriers only, subsequently remembered words were linked to increased hippocampal activity. Across all participants, increased pupil diameter differentiated subsequently remembered from forgotten words, and neural activity covaried with pupil diameter in cuneus and precuneus. These effects were weaker in e4 carriers, and e4 carriers did not show greater pupil diameter to remembered words. In the recognition phase, genotype status also modulated hippocampal activity: here, however, e4 carriers failed to show the conventional pattern of greater hippocampal activity to novel words.ConclusionsOverall, neural activity changes were unstable in e4 carriers, failed to respond to novelty, and did not link strongly to cognitive effort, as indexed by pupil diameter. This provides further evidence of abnormal hippocampal recruitment in young adult e4 carriers, manifesting as both up and downregulation of neural activity, in the absence of behavioral performance differences.

Ocular safety of propiverine hydrochloride in elderly patients with primary open- and narrow-angle glaucoma .

Propiverine hydrochloride (P4) is an antimuscarinic drug used in overactive bladder syndrome. Two studies were performed: one in 24 patients with open-angle glaucoma (OAG) treated with topical β-blockers, one in 24 patients with narrow-angle glaucoma (NAG) treated with pilocarpine ± topical β-blockers. Patients were treated in randomized, placebo-controlled, double-blind parallel-group fashion (15:9 attribution to P4 vs. placebo (PL)). Single-blind PL dose in the morning of day 1 for baseline; double-blind 15 mg P4 or matched placebo t.i.d. from the afternoon of day 1 until the morning of day 7. In the morning of day 7, trough mean serum P4 concentrations were 169.4 ng/mL (CV (coefficient of variation): 0.55) and 140.7 ng/mL (CV: 0.56) in OAG and NAG; at 3:15 hours after dosing: 237.4 ng/mL (CV: 0.47) and 212.4 ng/mL P4 (CV: 0.38), respectively. P4-treatment led to a prompt (OAG) or more gradient (NAG) increase in pupil diameter (PUD), with a maximum difference from PL of 0.97 mm (95% confidence interval (CI): 0.67 - 1.27) and 0.87 mm (95% CI: 0.36 - 1.39) in OAG and NAG, respectively. However, there was no average increase in intraocular pressure (IOP) or increase in noteworthy safety-relevant individual IOP values (or changes thereof). There was no effect on visual acuity or accommodation. 1-week treatment with P4 appeared to be safe 1) in OAG patients treated with topical β-blockers and 2) in NAG patients treated with topical pilocarpine ± β-blockers, irrespective of whether the eyes had previously been treated with glaucoma surgery or laser therapy. .

Effect of Pupil Size on Wavefront Refraction during Orthokeratology.

It has been hypothesized that central and peripheral refraction, in eyes treated with myopic overnight orthokeratology, might vary with changes in pupil diameter. The aim of this work was to evaluate the axial and peripheral refraction and optical quality after orthokeratology, using ray tracing software for different pupil sizes. Zemax-EE was used to generate a series of 29 semi-customized model eyes based on the corneal topography changes from 29 patients who had undergone myopic orthokeratology. Wavefront refraction in the central 80 degrees of the visual field was calculated using three different quality metrics criteria: Paraxial curvature matching, minimum root mean square error (minRMS), and the Through Focus Visual Strehl of the Modulation Transfer Function (VSMTF), for 3- and 6-mm pupil diameters. The three metrics predicted significantly different values for foveal and peripheral refractions. Compared with the Paraxial criteria, the other two metrics predicted more myopic refractions on- and off-axis. Interestingly, the VSMTF predicts only a marginal myopic shift in the axial refraction as the pupil changes from 3 to 6 mm. For peripheral refraction, minRMS and VSMTF metric criteria predicted a higher exposure to peripheral defocus as the pupil increases from 3 to 6 mm. The results suggest that the supposed effect of myopic control produced by ortho-k treatments might be dependent on pupil size. Although the foveal refractive error does not seem to change appreciably with the increase in pupil diameter (VSMTF criteria), the high levels of positive spherical aberration will lead to a degradation of lower spatial frequencies, that is more significant under low illumination levels.

Central cholinergic pathway involvement in the regulation of pupil diameter, blink rate and cognitive function

Anticholinergic medications can exert their effects by acting on muscarinic receptors, which mediates the function of acetylcholine in the central nervous system. Acetylcholine plays a number of roles, particularly in regard to the control of muscle activity and normal cognitive functioning. Eighteen subjects were recruited into the human, double-blind, placebo-controlled, four-way crossover study. Pupil diameter and blink rate were assessed at rest while eye tracking technology recorded eye characteristics. Thereafter a cognitive task was performed, where pupil size and blink rate were once again measured. Assessments were performed pre-ingestion, 0.5h and 2h following the ingestion of a strong centrally acting anticholinergic (promethazine hydrochloride), a moderate centrally acting anticholinergic (hyoscine hydrobromide), an anticholinergic devoid of central effects (hyoscine butylbromide) and placebo. At rest, hyoscine hydrobromide was the only medication to increase pupil diameter and no drug intervention influenced blink rate. During performance of the cognitive task, hyoscine hydrobromide increased pupil diameter and promethazine increased blink rate. Promethazine was the only medication to influence the modified attention network test (ANT) by increasing the conflict effect and grand mean reaction time (RT). Pupil diameter and blink rate were both influenced by the central anticholinergics during performance of the cognitive test, thus highlighting the importance of central cholinergic pathways in the control of pupil diameter and blink rate. The collective effects of central anticholinergics on the modified ANT and on pupil diameter and blink rate during its performance, conveys the importance of central cholinergic pathways in cognitive function.

The effects of time pressure on driver performance and physiological activity: A driving simulator study

Speeding because of time pressure is a leading contributor to traffic accidents. Previous research indicates that people respond to time pressure through increased physiological activity and by adapting their task strategy in order to mitigate task demands. In the present driving simulator study, we investigated effects of time pressure on measures of eye movement, pupil diameter, cardiovascular and respiratory activity, driving performance, vehicle control, limb movement, head position, and self-reported state. Based on existing theories of human behavior under time pressure, we distinguished three categories of results: (1) driving speed, (2) physiological measures, and (3) driving strategies. Fifty-four participants drove a 6.9-km urban track with overtaking, car following, and intersection scenarios, first with no time pressure (NTP) and subsequently with time pressure (TP) induced by a time constraint and a virtual passenger urging to hurry up. The results showed that under TP in comparison to NTP, participants (1) drove significantly faster, an effect that was also reflected in auxiliary measures such as maximum brake position, throttle activity, and lane keeping precision, (2) exhibited increased physiological activity, such as increased heart rate, increased respiration rate, increased pupil diameter, and reduced blink rate, and (3) adopted scenario-specific strategies for effective task completion, such as driving to the left of the lane during car following, and early visual lookout when approaching intersections. The effects of TP relative to NTP were generally large and statistically significant. However, individual differences in absolute values were large. Hence, we recommend that real-time driver feedback technologies use relative instead of absolute criteria for assessing the driver’s state.

Pupil diameter changes reflect difficulty and diagnostic accuracy during medical image interpretation.

BackgroundNo automated methods exist to objectively monitor and evaluate the diagnostic process while physicians review computerized medical images. The present study tested whether using eye tracking to monitor tonic and phasic pupil dynamics may prove valuable in tracking interpretive difficulty and predicting diagnostic accuracy.MethodsPathologists interpreted digitized breast biopsies varying in diagnosis and rated difficulty, while pupil diameter was monitored. Tonic diameter was recorded during the entire duration of interpretation, and phasic diameter was examined when the eyes fixated on a pre-determined diagnostic region during inspection.ResultsTonic pupil diameter was higher with increasing rated difficulty levels of cases. Phasic diameter was interactively influenced by case difficulty and the eventual agreement with consensus diagnosis. More difficult cases produced increases in pupil diameter, but only when the pathologists’ diagnoses were ultimately correct. All results were robust after adjusting for the potential impact of screen brightness on pupil diameter.ConclusionsResults contribute new understandings of the diagnostic process, theoretical positions regarding locus coeruleus-norepinephrine system function, and suggest novel approaches to monitoring, evaluating, and guiding medical image interpretation.

Evaluation of anterior segment parameters using Scheimpflug technology during the Valsalva maneuver in patients with keratoconus.

This study aimed to explore the effects of the Valsalva maneuver (VM) on ectatic corneas during anterior segment tomography scans using a Scheimpflug camera. This prospective observational study included 100 eyes of 50 patients with bilateral keratoconus (KC). Anterior segment tomography was first performed when the patients were in a resting position and immediately repeated as the participant performed VM. Scheimpflug images were taken using a Pentacam®. The mean age of the participants was 24.14 ± 6.59 years. Of the 100 eyes included in the study, 7% had stage 1 KC, 47% had stage 2 KC, 32% had stage 3 KC, and 14% had stage 4 KC. The indices of KC were not significantly affected by VM. Similarly, no statistically significant differences were found between the stages of KC, or with the mean pachymetric progression index during VM. Pupil diameter showed a statistically significant increase during VM (p=0.017). There was a statistically significant decrease in the anterior chamber angle measurement during VM (p=0.001). Maximum curvature power in the front of the cornea decreased more during VM in stage 4 KC than for the other stages (p=0.014). No changes associated with VM were found in the KC indices or the stage of the disease. However, an increase in pupil diameter and a decrease in anterior chamber angle value were found. These changes were comparable to values obtained from previous studies performed on normal corneas.

Effect of hemodialysis on intraocular lens power calculation

Background To evaluate changes in ocular biometric parameters after hemodialysis (HD) in patients with end-stage renal disease (ESRD). Methods Forty eyes of 40 patients undergoing HD were included in this cross-sectional study. Keratometry (K) readings, white-to-white (WTW) distance, central corneal thickness (CCT), anterior chamber depth (ACD), pupil diameter, lens thickness (LT), axial length (AL), and intraocular lens (IOL) power calculation were measured with Lenstar LS 900 (Haag Streit AG, Koeniz, Switzerland) before and after hemodialysis. Intraocular pressure (IOP) was measured with a non-contact tonometer (Tonopachy NT-530P, Nidek Co., LTD, Tokyo, Japan). Main outcomes were changes in biometric parameters after HD. Reliability of the measurements (intraclass correlation coefficients (ICCs)) and the effect size (Cohen’s d) were also calculated. Results Mean difference in AL before and after HD was −0.041 ± 0.022 mm with ICCs > 0.90 (p < 0.001 and Cohen’s d = 0.06). Pupil diameter was also significantly different before (4.28 ± 0.81 mm) and after (4.44 ± 0.79 mm) HD with ICCs > 0.90 (p = 0.041 and Cohen’s d = 0.20). Hemodialysis had no significant effect on K readings, WTW distance, CCT, ACD, LT, or IOP. Conclusion Axial length and pupil diameter increase after HD with small effect size, while HD does not significantly affect IOL power calculations.

Change of the focused depth of biconvex Toric intraocular lens in Hwey-Lan Liou schematic eye

Background Toric intraocular lens (IOL) has two optical powers in two perpendicular directions, and it could result in many different optic performance from spherical IOL. Objective This study was to evaluate the depths of focus of spherical, aspherical and Toric IOL under polychoromatic light by Hwey-Lan Liou schematic eye. Methods Hwey-Lan Liou schematic eye was created using Zemax software, and the alterations of focusing depth of Tecnis ZA9003 IOL (a spherical IOL), SN60AT IOL(a aspherical IOL), Arcysof Toric IOL were evaluated and compared based on Hwey-Lan Liou schematic eye by ray tracing method. Results The modulation transfer function (MTF) was perfect and the depth of defocus was equal under the zero defocus and under the pupil diameter of 3 mm with symmetrical focus curve in plus or minus two-axis in both spherical IOL and Toric IOL. The MTF decreasing with 5 mm pupil compared with that with 3 mm pupil. The MTF was declined under the pupil diameter of 5 mm compared with 3 mm in spherical IOL and Toric IOL along with the decrease of focus depth and the drifting of MTF toward negative axis. However, only the focus depth was decreased but MTF appeared to be stable in aspherical IOL. Conclusions Toric IOL and spherical IOL exhibit similar trends in focus depth change, and their focus depths decrease with the increase of pupil diameter. In addition, Toric IOL and spherical IOL show good light focus during minus defocus shifting. Key words: Lenses, intraocular; Astigmatism; Eye, artificial; Focused depth

Improving the performance of an EEG-based motor imagery brain computer interface using task evoked changes in pupil diameter.

For individuals with high degrees of motor disability or locked-in syndrome, it is impractical or impossible to use mechanical switches to interact with electronic devices. Brain computer interfaces (BCIs) can use motor imagery to detect interaction intention from users but lack the accuracy of mechanical switches. Hence, there exists a strong need to improve the accuracy of EEG-based motor imagery BCIs attempting to implement an on/off switch. Here, we investigate how monitoring the pupil diameter of a person as a psycho-physiological parameter in addition to traditional EEG channels can improve the classification accuracy of a switch-like BCI. We have recently noticed in our lab (work not yet published) how motor imagery is associated with increases in pupil diameter when compared to a control rest condition. The pupil diameter parameter is easily accessible through video oculography since most gaze tracking systems report pupil diameter invariant to head position. We performed a user study with 30 participants using a typical EEG based motor imagery BCI. We used common spatial patterns to separate motor imagery, signaling movement intention, from a rest control condition. By monitoring the pupil diameter of the user and using this parameter as an additional feature, we show that the performance of the classifier trying to discriminate motor imagery from a control condition improves over the traditional approach using just EEG derived features. Given the limitations of EEG to construct highly robust and reliable BCIs, we postulate that multi-modal approaches, such as the one presented here that monitor several psycho-physiological parameters, can be a successful strategy in making BCIs more accurate and less vulnerable to constraints such as requirements for long training sessions or high signal to noise ratio of electrode channels.

Losses as ecological guides: Minor losses lead to maximization and not to avoidance

Losses are commonly thought to result in a neuropsychological avoidance response. We suggest that losses also provide ecological guidance by increasing focus on the task at hand, and that this effect may override the avoidance response. This prediction was tested in a series of studies. In Study 1a we found that minor losses did not lead to an avoidance response. Instead, they guided participants to make advantageous choices (in terms of expected value) and to avoid disadvantageous choices. Moreover, losses were associated with less switching between options after the first block of exploration. In Study 1b we found that this effect was not simply a by-product of the increase in visual contrast with losses. In Study 1c we found that the effect of losses did not emerge when alternatives did not differ in their expected value but only in their risk level. In Study 2 we investigated the autonomic arousal dynamics associated with this behavioral pattern via pupillometric responses. The results showed increased pupil diameter following losses compared to gains. However, this increase was not associated with a tendency to avoid losses, but rather with a tendency to select more advantageously. These findings suggest that attention and reasoning processes induced by losses can out-weigh the influence of affective processes leading to avoidance.

An Evaluation of Effects of Different Mydriatics on Choroidal Thickness by Examining Anterior Chamber Parameters: The Scheimpflug Imaging and Enhanced Depth Imaging-OCT Study.

Aim. To assess the effects of mydriatics commonly used in clinical practice on choroidal thickness and anterior chamber change. Methods. This was a prospective, randomized, controlled, double-blinded study including a single eye of the participants. The subjects were assigned into 4 groups to receive tropicamide 1%, phenylephrine 2.5%, cyclopentolate 1%, and artificial tears. At the baseline, anterior chamber parameters were assessed using a Pentacam Scheimpflug camera system, and choroidal thickness (CT) was measured using a spectral-domain OCT with Enhanced Depth Imaging (EDI) modality. All measurements were repeated again after drug administration. Results. Increases in pupil diameter, volume, and depth of anterior chamber were found to be significant (p = 0.000, p = 0.000, and p = 0.000, resp.), while decreases in the choroidal thickness were found to be significant in subjects receiving mydriatics (p < 0.05). Conclusions. The study has shown that while cyclopentolate, tropicamide, and phenylephrine cause a decrease in choroidal thickness, they also lead to an increase in the volume and depth of anterior chamber. However, no correlation was detected between anterior chamber parameters and choroidal changes after drug administration. These findings suggest that the mydriatics may affect the choroidal thickness regardless of anterior chamber parameters. This study was registered with trial registration number 2014/357.

Topical caffeine induces mydriasis in animals under ketamine‐xylaxine anesthesia

AbstractPurpose To determine the effect of topically applied caffeine on the pupil diameter during ketamine‐xylazine anesthesiaMethods Six‐week‐old Sprague‐Dawley rats were anesthetized with ketamine xylazine intraperitoneally. Caffeine, 72 mM, dissolved in vehicle, 9 mg/ml, hydroxypropylmethyl cellulose dissolved in water, or the vehicle only, was topically applied. Animals were kept under room light conditions. In experiment I, caffeine in vehicle was topically applied to one eye and vehicle only to the other eye in 10 animals. In experiment II, caffeine in vehicle was applied to both eyes in one group of 10 animals and vehicle only to another group of 10 animals. In both experiments, pupil diameter was measured on both eyes. Measurements were taken immediately after initiation of the anesthesia, and 10, 20, 40 and 60 min. later.Results In experiment I, vehicle only caused a slight transient increase of pupil diameter, peaking around 20 min. after initiation of anesthesia and then decreased below baseline. Caffeine in vehicle caused an initial fast decrease in pupil diameter and the decrease rate leveled out towards 60 min. after initiation of anesthesia. In experiment II, vehicle to both eyes induced a transient increase in pupil diameter that returned to baseline. Caffeine and vehicle on both eyes induced an exponentially declining decrease towards asymptote miosis. The miosis reversed to mydriasis after topical application of tropicamide 5 mg/ml.Conclusion Topically applied caffeine induces miosis in a ketamine‐xylazine anesthetized rat. There is some systemic effect on pupil diameter of the currently used topical application of caffeine. The miotic effect of topically applied caffeine is reversed by tropicamide.

Pupillary Dynamics Reveal Computational Cost in Sentence Planning

This study investigated the computational cost associated with grammatical planning in sentence production. We measured people's pupillary responses as they produced spoken descriptions of depicted events. We manipulated the syntactic structure of the target by training subjects to use different types of sentences following a colour cue. The results showed higher increase in pupil size for the production of passive and object dislocated sentences than for active canonical subject-verb-object sentences, indicating that more cognitive effort is associated with more complex noncanonical thematic order. We also manipulated the time at which the cue that triggered structure-building processes was presented. Differential increase in pupil diameter for more complex sentences was shown to rise earlier as the colour cue was presented earlier, suggesting that the observed pupillary changes are due to differential demands in relatively independent structure-building processes during grammatical planning. Task-evoked pupillary responses provide a reliable measure to study the cognitive processes involved in sentence production.

Comparison of Dynamic Changes in Anterior Ocular Structures Examined With Anterior Segment Optical Coherence Tomography in a Cohort of Various Origins

To identify risk factors associated with primary angle closure (AC) using anterior segment optical coherence tomography (ASOCT) measurements of the iris and to determine if these risk factors differ according to geographic origin. Anterior segment OCT images were collected on 267 persons (eyes) whose family origin was determined by a standardized method. In the 257 eyes with pupil diameter increase in the dark of 0.5 mm or more, findings were compared between bright light conditions and those in a dark room. In 130 eyes, comparison was made after pharmacological pupil dilation. After marking the position of the scleral spur, an automated program quantified many angle and iris parameters, with use of a manual method for a minority that the software could not analyze. Iris area in bright light was larger with increasing age (univariate regression, P = 0.0005), largest in European and African-derived, and smallest in Korean and Chinese eyes (multivariable regression, P = 0.0001), and was significantly larger in AC groups compared with normal and open angle glaucoma groups (univariate regression, P < 0.0001). The absolute iris area loss per mm pupil dilation was significantly less in Chinese persons than African-derived persons (multivariable regression, P < 0.05 adjusted Tukey). Furthermore, in persons with past acute AC attack, the baseline iris area was not different from others, but their iris area lost per millimeter dilation was significantly less than in persons without past acute AC attack (multivariable regression, P = 0.04). The odds of AC disease significantly increased in eyes with smaller percent iris area lost and percent iris area lost per millimeter pupil increase, but when adjusted for geographic origin, this was significant only in persons of Chinese origin (interaction regression model). Apparent gain of iris volume on pupil dilation, due to an artifact in calculation from iris area loss, may indicate a detrimental shift in iris tissue toward the angle. Chinese persons in this cohort had relatively low baseline iris area, but less loss of iris area on pupil dilation than other groups, a feature also associated with greater prevalence of past acute AC attack. Disproportionate peripheral redistribution of iris area on dilation may contribute to AC.

Natural Pupil Size and Ocular Aberration under Binocular and Monocular Conditions

Purpose: To investigate how activity of natural pupils under binocular and monocular conditions affect wave front aberrations. Materials and Methods: Eighteen eyes from 18 subjects (mean age 22.3 ± 0.8 years) were included in the study. The undilated pupil diameters under photopic conditions were measured using the FP-10000 (TMI, Japan) infrared pupillometer. Aberrometry measurements were performed using the KR-9000PW (Topcon, Japan) Hartmann- Shack wavefront sensor. Zernike coefficients were recalculated for the diameters of each pupil under binocular and monocular conditions using Schwiegerling’s algorithm. Multiple regression analysis was performed to analyze independent predictors of the change of higher-order aberration for 6.0 mm from the binocular to the monocular condition. The independent variables were the change of pupil diameter from binocular to monocular condition; binocular pupil diameter; total higher-order aberration for 6.0 mm, sphere, and cylinder. Results: Pupil diameter, total, total higher-order, coma-like, and spherical-like aberrations under monocular conditions were significantly greater than the binocular condition (all P<0.01). The multiple regression of analysis of variables showed that the change of total higher order aberration from the binocular to the monocular condition was related to the change of pupil diameter, and the amount of higher-order aberrations for 6.0 mm (P<0.05). Conclusion: The outcomes suggest that increased pupil diameter under monocular conditions produces higher wavefront aberrations than under binocular conditions, resulting in a degradation of retinal image quality. This effect is enhanced in eyes with greater higher order aberrations and pupil diameter

Retinal light distributions, the Stiles–Crawford effect and apodization

Analysis of retinal image formation for beams of coherent and incoherent radiation emphasizes the role of the Poynting vector's inclination with respect to the retinal image plane. Coherent beams interfere and give rise to a single Poynting vector that highlights the unique direction of incidence of energy flow, whereas multiple incoherent beams, especially incoherent extended sources in the pupil, generate electro-magnetic disturbances in the image plane each characterized by Poynting vectors of their own. As a result, the Stiles-Crawford diminution of luminant efficiency adds differently depending on the coherence of the entering light. Two practical considerations follow: first, in performing diffraction calculations for the retinal image from known wavefronts in the pupil plane, apodization terms should not be factored in, and, second, in principle, for perfect imaging in standard target viewing, Stiles-Crawford integration with increasing pupil diameter is not expected.

Utilidad de la pupilometría dinámica en el control de alcoholemia de los conductores

Pupillometry is becoming a relevant tool in Vision Sciences. So far, only a few studies have explored the relationship between pupil reflex measures and drug consumption. The aim of this study was to assess the applicability of dynamic mesopic pupillometry as an objective measurement method for the detection of blood alcohol levels above the legal limit. In a quasiexperimental design, 19 volunteers were asked to participate in two conditions (before and after alcohol intake). In session with alcohol intake, participants were asked to consume 27.5 ml of alcohol in 60 minute intervals for four hours. Pupillometry records were conducted by means of the Power Refractor II, using four types of light stimulation: white (5600 K), blue (450 nm), green (510 nm) and red (600 nm). The basal diameter of the pupil increased significantly for alcohol concentrations equal to or greater than 0.25 mg/l in exhaled breath. Moreover, the value of the amplitude for red light constriction also provided significant differences between the two conditions. These results are promising in the search for new methods to detect illegal alcohol levels among drivers. This study demonstrates that basal pupil diameter increase and amplitude response could be used as an alcohol consumption level indicator. However, further studies are necessary to validate this and other diagnose methods complementary to breathalyzer and other drugs tests.

Quantifying the impact of cross coverage on physician’s workload and performance in radiation oncology

PurposeTo quantitatively assess the difference in workload and performance of radiation oncology physicians during radiation therapy treatment planning tasks under the conditions of “cross coverage” versus planning a patient with whom they were familiar. Methods and MaterialsEight physicians (3 experienced faculty physicians and 5 physician residents) performed 2 cases. The first case represented a “cross-coverage” scenario where the physicians had no prior information about the case to be planned. The second exposure represented a “regular-coverage” scenario where the physicians were familiar with the patient case to be planned. Each case involved 3 tasks to be completed systematically. Workload was assessed both subjectively (perceived) using National Aeronautics and Space Administration-Task Load Index (NASA-TLX), and objectively (physiological) throughout the task using eye data (via monitoring pupil size and blink rate). Performance of each task and the case was measured using completion time. Subjective willingness to approve or disapprove the generated plan was obtained after completion of the case only. ResultsForty-eight perceived and 48 physiological workload assessments were obtained. Overall, results revealed a significant increase in perceived workload (high NASA-TLX score) and decrease in performance (longer completion time and reduced approval rate) during cross coverage. There were nonsignificant increases in pupil diameter and decreases in the blink rate during cross-coverage versus regular-coverage scenario. In both cross-coverage and regular-coverage scenarios the level of experience did not affect workload and performance. ConclusionsThe cross-coverage scenario significantly increases perceived workload and degrades performance versus regular coverage. Hence, to improve patient safety, efforts must be made to develop policies, standard operating procedures, and usability improvements to electronic medical record and treatment planning systems for “easier” information processing to deal with cross coverage, while recognizing strengths and limitations of human performance.

Contribution of the gradient refractive index and shape to the crystalline lens spherical aberration and astigmatism

The optical properties of the crystalline lens are determined by its shape and refractive index distribution. However, to date, those properties have not been measured together in the same lens, and therefore their relative contributions to optical aberrations are not fully understood. The shape, the optical path difference, and the focal length of ten porcine lenses (age around 6 months) were measured in vitro using Optical Coherence Tomography and laser ray tracing. The 3D Gradient Refractive Index distribution (GRIN) was reconstructed by means of an optimization method based on genetic algorithms. The optimization method searched for the parameters of a 4-variable GRIN model that best fits the distorted posterior surface of the lens in 18 different meridians. Spherical aberration and astigmatism of the lenses were estimated using computational ray tracing, with the reconstructed GRIN lens and an equivalent homogeneous refractive index. For all lenses the posterior radius of curvature was systematically steeper than the anterior one, and the conic constant of both the anterior and posterior positive surfaces was positive. In average, the measured focal length increased with increasing pupil diameter, consistent with a crystalline lens negative spherical aberration. The refractive index of nucleus and surface was reconstructed to an average value of 1.427 and 1.364, respectively, for 633 nm. The results of the GRIN reconstruction showed a wide distribution of the index in all lens samples. The GRIN shifted spherical aberration towards negative values when compared to a homogeneous index. A negative spherical aberration with GRIN was found in 8 of the 10 lenses. The presence of GRIN also produced a decrease in the total amount of lens astigmatism in most lenses, while the axis of astigmatism was only little influenced by the presence of GRIN. To our knowledge, this study is the first systematic experimental study of the relative contribution of geometry and GRIN to the aberrations in a mammal lens.