Pupil Size Variation Research Articles

Periodic Unilateral Eyelid Retraction in a Pediatric Patient

A healthy 11-year-old girl presented with right upper eyelid retraction since birth. An evaluation including thyroid function studies and neuroimaging was negative, and the patient was scheduled for a right levator recession to address the eyelid malposition. Intraoperatively, after the induction of inhalational general anesthesia, the patient displayed cyclic right upper eyelid retraction. Occurring in intervals of exactly 48 seconds, these cycles involved a rapid elevation of the right eyelid from a position of half-closure to a retracted position just above the superior limbus. There was no change in pupil size or eye position during these cyclic spasms, and the contralateral eyelid was unaffected. The patient underwent an uncomplicated levator recession, which improved the upper eyelid retraction. Postoperative testing, including external motility video and infrared pupillometry, demonstrated no cyclic variation in eyelid position, eye position, or pupil size in the waking state. This is a unique case of unilateral eyelid retraction with periodic spasms under conditions of anesthesia without a preexisting oculomotor paresis; it represents an unusual variation on congenital eyelid retraction and classically described cyclic oculomotor palsy.

Visual Evaluation of Different Multifocal Corneal Models for the Correction of Presbyopia by Laser Ablation

To evaluate the visual quality of two theoretical multifocal corneal models designed to correct presbyopia by corneal photoablation. Two theoretical multifocal corneal surfaces were analyzed by ray tracing: a central model (with a central zone for near vision and a peripheral zone for distance vision), and a peripheral model (with a central zone for distance vision and a peripheral zone for near vision). For both models, the effect of the size of the central zone and transition zone as well as the size of the pupil was evaluated. Our results show that a smaller transition zone favors total visual quality in both models. The optimal size of the central zone depends both on the size of the transition zone used as well as the model. However, both models responded similarly with respect to the variations in pupil size, providing the same visual quality although in an opposite way. This work shows that the optimal diameter of the central zone is smaller for the central model than for the peripheral model. Also, pupil size plays a fundamental role in achieving multifocality, showing that patient's pupil size should be thoroughly evaluated prior to multifocal refractive surgery.

N400 amplitude reduction correlates with an increase in pupil size.

Pupil dilation is classically associated with increase in cognitive load in humans. Here, we studied the potential link between human pupil dilation and meaning integration effort as indexed by event-related brain potentials (ERPs). We recorded pupil size variation and ERPs simultaneously while participants were presented with matching or unrelated picture–word pairs. Whilst relatedness in meaning between spoken words and pictures typically modulated ERPs, pupil size was also affected quickly after picture onset. Moreover, during the time-window associated with meaning integration, greater pupil dilation correlated with less negative N400 amplitudes elicited by unrelated pictures. Since pupil dilation has been linked to activity of the locus coeruleus–norepinephrine (LC–NE) system, these findings may provide new insights into the suggested link between human high-level cognitive function and activity of the LC–NE system.

Impact of iris pigment and pupil size in ultraviolet radiation cataract in rat

To investigate the effect of iris pigment and pupil size in ultraviolet radiation (UVR)-induced cataract. Brown-Norway rats (pigmented) and Fischer-344 rats (non-pigmented) were unilaterally exposed in vivo to 5 kJ/m(2) UVR. Each strain was split into two groups, each receiving either mydriatic (tropicamide) or miotic (pilocarpine) eye-drops. One week after exposure, the degree of ocular inflammation and damage in the anterior segment was determined. The lenses were extracted, photographed and the degree of forward light scattering (cataract) was quantified. The cataract types differed between the two strains. All Fischer rats developed macroscopically identifiable UVR cataract while only 41% of Brown-Norway rats did so. All groups except the miotic Brown-Norway developed significant light scattering. The Fischer rats developed 3-4-fold more lens light scattering than the Brown-Norway rats. The miotic Fischer group exhibited significantly more light scattering than the mydriatic Fischer group. There was no significant difference in light scattering between the two Brown-Norway groups. There was a correlation between ocular inflammation and degree of light scattering, with Brown-Norway rats exhibiting less inflammation and lens light scattering. Pigmented rats develop less UVR cataract and less ocular inflammation than non-pigmented rats. Pupil size plays a smaller role in UVR cataract development in pigmented rats than in non-pigmented. The role of UVR-induced ocular inflammation in cataract development is still ambiguous.

Optical filters influence on pupil size according to their material and spectral characteristics

Abstract Purpose To evaluate pupil size variations induced by optical filter by using filters with different materials and spectral characteristics, focussing on UV and blue light transmission properties of the filters Methods 220 pupil measurements (20 eyes, 20‐55 years old) were made using the pupillometer Procyon P2000SA at high Mesopic level (4.0lux). 10 filters of varying transmittance (visible, 4%‐65%, 5 filters UV‐transmitting and 5 filters UV‐absorbing) were used in a randomised way. 5 filters (UV‐transmitting) were dye‐coated polyester films with a substrate of PET (polyethylene terephthalate) and the another 5 filters (UV‐absorbing) were Ophthalmic CR39 lenses with a tinted coating in order to get the same absorbing characteristics than the PET filters. Measurements in the absence of a filter served as control Results Significant results on pupil size variation were obtained with lower UV and blue light transmittance filters (F14, F15 and F16; p=0.00) for both materials, PET and CR39 (Mydriasis obtained: F14R=13.99%; F15R=17.57%; F16R=22.90%; F14E=23.95%; F15E=22.69%; F16E=29.87%). Also significant differences in mydriasis‐induced by the filter were obtained when materials and blue‐light transmission properties were compared for filters 14 and 16 (PET vs. CR39: F14 (p=0.006), F16 (p=0.0167) Conclusion Filters with similar visible but different UV and/or blue‐light transmission properties significantly produce variations in pupil size at high Mesopic condition (4.0lux). Differences obtained in mydriasis‐induced by the filter depend not only on the material of the filter, but also the UV and/or blue‐light transmitted by the filter

Influence of ophthalmic lenses in the illuminance originated at a peripheral glare source and reaching the eye

To study the influence of glare on the visual performance of a subject wearing an ophthalmic lens, it is useful to know how the lens affects the illuminance reaching the eye. In this paper, considering spherical standard ophthalmic lenses and defining the relative illuminance, E r, as the quotient between the illuminance at the cornea with and without lens, a methodology to evaluate E r in terms of easily determined parameters is developed. Three effects are considered, pupil size variation of the system with and without lens; lateral shifts of rays transmitted through the lens and reflections at the lens. Calculations are experimentally verified employing 5 organic ophthalmic lenses of ±6; ±4 and 0.12 dioptres and 2 glass plane parallel plates 1.95 and 6.6 mm thick. Using a photometer whose sensor is 12 mm apart from the lens and 740 mm apart from a glare source subtending an eccentricity angle of 9.6°, it results E r=1.204 for the 6 dioptres lens and E r=0.803 for the −6 dioptres one if sensor diameter is 10 mm while, for a 719 mm distance and a 10° angle, E r=0.922 for the thin plate and a 30 mm sensor and E r=1.006 for the thick plate and a 10 mm sensor. Experimental and theoretical results differ in less than 3%.

A New Computer Vision Based Polygraph System

In this paper, we describe a new polygraph system which is based on computer vision technologies. The underpinning idea is to detect pupil size variation from a sequence of images. Based on the variation of the pupil size, we can detect for truth or deception. We have experimented with our system and proved its effectiveness. Compared with traditional polygraph techniques, this is the best computer vision based system to date. It is much simpler compared to old systems and is easier to implement. Keywords: Polygraph, image feature extraction, shape analysis

Visual aftereffects

Visual aftereffects

Changes in Pupil Dynamics at High Altitude—An Observational Study Using a Handheld Pupillometer

Gross pupil dynamics are used as an indirect measure of brain function. Changes in hypoxia and intracranial pressure are thought to alter pupil responses to light. This study assessed a portable handheld pupil measuring device (pupillometer) in the field investigating the changes in pupil size, speed of reaction, and rate of constriction/dilatation with hypoxia induced by changes in altitude. A correlation between pupil dynamics and acute mountain sickness was sought. Seventeen volunteers were studied following acute exposure to 3450 m and then during a trek to 4770 m in Ladakh, India. The pupillometer was used to record maximum and minimum pupil diameter in response to a standard light source with calculation of latency, constriction and dilatation velocities. Acute mountain sickness (AMS) was recorded using Lake Louise self completed questionnaires both in the morning and afternoon on each day. Acute altitude exposure resulted in a significant reduction of percentage change in pupil size (36.5% to 24.1% p=<0.001), significant delay in pupillary contraction (latency; 0.208 to 0.223 seconds p=0.015) and a significant slowing of the rate of contraction (constriction velocity; -2.77 mm/s to -1.75 mm/s p=0.012). These changes reverted to normal during a period of acclimatization. A significant diurnal variation in pupil size was also observed. There was no significant difference between subjects with and without AMS. The handheld pupillometer is a suitable robust tool for monitoring changes in pupil dynamics in the field. With acute exposure to hypobaric hypoxia associated with an ascent to a moderate altitude, there is a general slowing of pupil function which reverts to normal within a few days of acclimatization. There appears to be a marked diurnal variation in pupil size. The measurements clearly demonstrated an effect of hypoxia on cerebral function, but these changes did not relate to moderate AMS.

Effect of the interposition of optical filters with different visible light transmittances in mesopic and scotopic condition pupil size

Abstract Purpose To determine how can the pupil size, in mesopic and scotopic condition, be affected by the interposition of optical filters. Also, the variability of the effect of these optical filters due to each filter’s different visible light transmittance. Methods The transversal study included data from 56 eyes of 28 subjects. To measure the different pupil size, in high mesopic, low mesopic and scotopic condition, was used a digital binocular infrared pupillometer. The obtained pupil size’s measurements, without filter, were compared with the results after the insertion of the different optical filters used: 16 filters with different transmittances (from 82% to 5%). Results Some filters, 5 of the 16, with different transmittances, 63%, 17%, 8%, 6% and 5%, caused significant variations in the pupil size in mean mesopic condition. The 2 highest transmittance’s filters, 63% and 17%, between these 5 filters, which produced significant results (p&lt;0.00, high mesopic condition, 4.0lux), were the ones that led a higgest pupil size variation, in the 3 different light conditions. Conclusion The influence of some optical filters in pupil size variation, was confirmed. This effect on pupil size was significant only in high mesopic condition, and it was independent of each filter’s different visible light transmittance.

Sources of error in intraocular lens power calculation

To identify and quantify sources of error in the refractive outcome of cataract surgery. AMO Groningen BV, Groningen, The Netherlands. Means and standard deviations (SDs) of parameters that influence refractive outcomes were taken or derived from the published literature to the extent available. To evaluate their influence on refraction, thick-lens ray tracing that allowed for asphericity was used. The numerical partial derivative of each parameter with respect to spectacle refraction was calculated. The product of the partial derivative and the SD for a parameter equates to its SD, expressed as spectacle diopters, which squared is the variance. The error contribution of a parameter is its variance relative to the sum of the variances of all parameters. Preoperative estimation of postoperative intraocular lens (IOL) position, postoperative refraction determination, and preoperative axial length (AL) measurement were the largest contributors of error (35%, 27%, and 17%, respectively), with a mean absolute error (MAE) of 0.6 diopter (D) for an eye of average dimensions. Pupil size variation in the population accounted for 8% of the error, and variability in IOL power, 1%. Improvement in refractive outcome requires better methods for predicting the postoperative IOL position. Measuring AL by partial coherence interferometry may be of benefit. Autorefraction increases precision in outcome measurement. Reducing these 3 major error sources with means available today reduces the MAE to 0.4 D. Using IOLs that compensate for the spherical aberration of the cornea would eliminate the influence of pupil size. Further improvement would require measuring the asphericity of the anterior surface and radius of the posterior surface of the cornea.

Analyzing head roll and eye torsion by means of offline image processing

Ocular torsion is a key problem in the understanding of many visual perceptual effects. However, since it is difficult to record, its integration with other sensorimotor signals is still poorly understood. Unfortunately, eyetracker systems are generally not dedicated to the monitoring of eye torsion. In addition, the classical methods used with video-based systems present some limits in the accuracy of torsion calculation. These limits are especially related to the detection of pupil center and the effects of pupil size changes. This article aims at (1) proposing a solution to analyze ocular torsion together with head roll using EyeLink II or similar equipment, (2) reviewing and adapting classical polar cross-correlation methods in order to improve the accuracy of torsion measurement, (3) providing a lower-cost method compared with the existing ones. Video sequences issued from the EyeLink II host computer monitor were recorded by means of a second computer equipped with a video acquisition card and converted into image sequences. Images were analyzed with algorithms of pupil center detection (median-based algorithm), torsion analysis (adapted polar cross-correlation method which takes into account pupil size variations) and marker tracking (head roll analysis). This method was tested on virtual eye images. Results are discussed with respect to other algorithms found in the literature.

In Vivo Gene Delivery in the Retina Using Polyethylenimine

In Vivo Gene Delivery in the Retina Using Polyethylenimine

Comparison of two pupillometers in determining pupil size for refractive surgery

To compare a handheld and a digital pupillometer in determining pupil size in a population of refractive surgery candidates (group 1) and after implantation of an Artisan phakic intraocular lens (PIOL) for correction of myopia (group 2). Pupil size was measured with the Colvard and Procyon pupillometers in 121 eyes in group 1 and 83 eyes in group 2. Pupil sizes measured with the Colvard device were compared with the scotopic, mesopic-low and mesopic-high measurements taken with the Procyon pupillometer in both groups. Analysis of comparison between pupil measurements was performed according to methods described by Bland and Altman. The mean Colvard scotopic pupil diameter, scotopic, mesopic-low and mesopic-high Procyon pupil diameters were 5.86 +/- 0.81 mm, 6.42 +/- 0.88 mm, 5.55 +/- 0.95 mm and 4.21 +/- 0.73 mm in group 1 and 5.32 +/- 0.67 mm, 6.14 +/- 0.81 mm, 5.33 +/- 0.78 mm and 4.02 +/- 0.55 mm in group 2, respectively. The Colvard diameter compared most favourably with the Procyon mesopic-low diameter (group 2; p = 0.78). Measurements of pupil diameter with the Colvard pupillometer correlated best with measurements taken by the Procyon pupillometer under standardized mesopic-low light conditions. We believe that digital binocular infrared pupillometry is advantageous for obtaining standardized measurements of pupil size.

Determining scotopic pupil size

Reply: We thank Cheng and coauthors for their comments on our comparison of devices to determine scotopic pupil sizes. The Zywave unit used by them (commercial software 5.09) is different than the one used in our study (software 4.45SP2). Using the pupillometry function, software 5.09 has no fixation target light and the infrared laser runs continuously at 2 μw of power during the measurement. Software 4.45SP2 has no fixation target light, and the infrared laser runs at 2 μw continuously and then at 35 μw for 100 ms during each measurement. In our study, the measurement was the diameter of 3 averaged wavefront readings. However, even in the continuously running setup of the commercial system, there is variation in pupil size due to hippus that is on the order of the changes in pupil size one sees between the 3 measurements. Day-to-day variations may be larger than the differences Cheng and coauthors question in our measurements. It might be correct to use the largest recorded pupil size rather than an average for a better representation of the scotopic pupil size, but in the study by Cheng and coauthors, the mean Zywave measurement was compared to the scotopic Procyon measurement, which represents the mean and standard error of 10 images acquired in 2 seconds at an illuminace level of 0.04 to 0.07 lux.1 Thomas Kohnen MD Evdoxia Terzi MD Thomas Kasper MD Eva-Maria Kohnen MD Jens Bühren MD

Pupil size variation as an indication of affective processing

The present objective was to investigate pupil size variation during and after auditory emotional stimulation. Thirty subjects’ (15 females and 15 males) pupil responses were measured while listening to 10 negative and 10 positive highly arousing sounds (e.g. a baby crying and laughing), and 10 emotionally neutral sounds (e.g. regular office noise). The subjects also rated their subjective experiences related to the stimuli. The results showed that the pupil size was significantly larger during both emotionally negative and positive stimuli than during neutral stimuli. The results for the time period of 2 s following the stimulus offset showed that pupil size was significantly larger after both negative and positive than neutral stimulation. These results suggest that the autonomic nervous system is sensitive to highly arousing emotional stimulation. The subjective ratings confirmed that the stimuli influenced the subjects’ emotional experiences as expected. Further analyses showed that female subjects had significantly larger pupil responses than males only to neutral stimuli and only during the auditory stimulation. In sum, our results showed that systematically chosen stimuli significantly affected the subjects’ physiological reactions and subjective experiences. It could be possible to use pupil size variation as a computer input signal, for example, in affective computing. Auditory emotion-related cues could also be utilized to modulate the user's emotional reactions.

Normal variation in, and effect of 2% pilocarpine on, intraocular pressure and pupil size in female horses

Abstract Objective To determine normal variation in, and effect of 2% pilocarpine hydrochloride on, intraocular pressure (IOP) and pupil size in female horses during a specified period. Animals 10 female horses with normotensive eyes. Procedure IOP and horizontal and vertical pupil size were measured on a single day between 8 am and 8 pm at hours 0, 0.5, 1, 2, 4, 6, 8, 10, and 12. Measurements were repeated after single-dose application of 2% pilocarpine to both eyes. IOP and pupil size were measured at 8 am and noon in a 5-day experiment of twice-daily application of 2% pilocarpine. Results Variation in IOP and pupil size was not significant between 8 am and 8 pm. Change in IOP or pupil size after a single dose of 2% pilocarpine also was not significant. In the multiple-dose experiment, the IOP at noon on the fifth day was significantly higher than the IOP in the morning on the first and second days. The IOP in the morning on the fifth day was significantly higher than the IOP in the morning and at noon on the first and second days. The IOP at noon on the fourth day was significantly higher than the morning IOP on the first and second days and at noon on the first day. The decrease in vertical pupil size was significant. Conclusions Between 8 am and 8 pm, variation in IOP and pupil size in normotensive eyes of horses is not significant. Two percent pilocarpine does not significantly change IOP between 8 am and 8 pm in clinically normal horses after a single dose or multiple twice-daily applications. After multiple twice-daily applications, a trend toward an increase in IOP was seen, and the decrease in vertical pupil size was significant. (Am J Vet Res 1998;59:1459–1462)

The eyes, the brain, and cardiac resuscitation

The mechanisms and neurological pathways governing pupil size and reactivity are complex and still not fully understood in brain damage and disease [l]. Until very recently ‘widely dilated fixed pupils’ were generally accepted as a reliable sign of irreversible brain damage and a strong justilication for abandoning unsuccessful cardiopulmonary resuscitation (CPR), despite the wide variation in pupil size in this context and their longrecognised unreliability as a guide to cerebral oxygenation and integrity, including brain death [2-41. Whilst a reduction in pupil size is one of the most valuable signs of effective CPR, and often more forceful chest compression can delay pupil enlargement in protracted resuscitation, so far as I know there has been no clinical study on the relationship between pupil size and cerebral blood flow in this situation. A change which is surely long overdue is the final abandonment of still widely used terms (even in the literature) to describe pupil size, such as ‘small’, ‘moderately constricted’, ‘widely dilated’ and so on in favour of accurate assessment in millimetres [4], as has long been standard practice with the Glasgow Coma Score [5]. As to ‘widely dilated’ (2 8 mm diameter) pupils being ‘fixed’, do we ever see pupils of this size in this situation react to light, since the reflex seems to be abolished by severe cerebral ischemia, and reappears only as the pupils return to normal size (~6 mm) and then not invariably in CPR? My personal experience suggests that as in general anaesthesia a positive eyelash reflex during CPR signifies that consciousness is only slightly depressed. It also suggests the brain is intact and the patient will swiftly regain consciousness once satisfactory heart action returns [4]. However, it generally disappears when CPR lasts for more than several minutes. The light reflex is a valuable sign in trauma patients [l] but how useful and how reliable a guide to brain status is it in CPR, and how does it compare with monitoring the eyelash reflex and pupil size? The concept of a protective penumbra during brain ischemia, between 10 and 30% of normal cerebral blood flow (CBF), structural integrity with functional silence [6], offers valuable insights into the possible impact of CPR on the brain [7]. It is likely that each part of the brain has its own critical flow value, highest in selectively vulnerable areas, in particular the cerebral cortex, its filter the reticular formation of the thalamus and the hippocampus [8-lo]. It is also likely the ischemic penumbra is, at least initially, flow time-dependant [l 11, its value rising as CPR continues (Fig. 1). One large study [ 121 has shown that provided CPR starts within about 5-6 min of cardiac arrest and

The effect of pupil size on static and dynamic measurements of accommodation using an infra-red optometer.

The study examines to what degree the output of the Canon Auto-ref R1 infra-red (IR) optometer is affected by variations in pupil size for both static measurement of refractive error and for continuous recording of accommodation when switched to its modified mode of operation. In the normal static mode of operation the measurement of refractive state simply depends on the position of the peak photodetector output for each of three meridians: it does not depend on signal amplitude and hence pupil size. However, in continuous mode the actual output of a single photodiode is measured and the measurement is susceptible to changes in pupil size that occur within the area of the exit pupil utilized by the instrument. Using static and dynamic recording on model and human eyes the study shows that a 10% reduction in output signal relative to the maximum output level (for a constant stimulus) occurs for pupil sizes of 3.9 mm. The relatively small exit pupil has important advantages with regard to the use of mydriatic drugs and task-induced changes in pupil diameter.

Effect of pupil size on kinetic visual field measurements

We determined visual field size as a function of pupil size by repeated measurements of Goldmann fields with an I2 target in the same subjects using contact lenses with different sized artificial pupils. Increasing pupil size from 3 to 6.8 mm increases visual field size from 2.79 to 3.34 steradians, an average increase of 19.7 per cent; a control experiment suggested that the major part of this effect can be explained by reduction of retinal illuminance produced by the variation in pupil size.