Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PUPILS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2002

Effect of asphyxia on the pupils of brain dead subjects.

The pupils dilate following cardiac arrest but the mechanism is unknown. If pupillary dilation represents inadequate blood supply to the midbrain, pupil size might be a rough guide to the adequacy of the resuscitation effort. The brain dead organ harvest patient presents a unique opportunity to study pupillary activity in the absence of an intact midbrain and to examine the effects of asphyxia on the pupil. Because the midbrain is dead in these subjects, the pupil has no supraspinal autonomic control and following aortic cross clamp, no blood can be delivered to the orbit. Ten brain dead patients scheduled for organ harvest were studied. Pupil size was measured from the right eye every minute for 9 min before and every minute for 10 min following aortic cross-clamp. Dapiprazole eye drops were instilled into the left eye at least 1 h before cross clamp in five cases and pupillary measurements were intermittently taken before and after cross clamp. Pupil size was stable before cross clamp. Following cross clamp, the pupil dilated in all cases, reaching 10.6 mm in one case. Mean dilation was 1.8+/-0.9 mm. Time to peak dilation was 4.3+/-1.4 min and latency of dilation was 1.4+/-1.2 min. Dapiprazole eye drops prevented the pupillary dilation in contralateral eye of the five cases in which it was used. The cause of this sympathetic activity is either a short burst of neuronal activity in the peripheral sympathetic system innervating the dilator muscle, or release of stored norepinephine from the presynaptic terminals, as asphyxia intervenes.

Adrenergic alpha-Antagonists↗
PubMed2001

Effect of preoperative pupil measurements on glare, halos, and visual function after photoastigmatic refractive keratectomy.

PURPOSE: To prospectively assess the effect of preoperative variables such as pupil size on glare, halos, and visual function after photoastigmatic refractive keratectomy (PARK). SETTING: Department of Ophthalmology, Stanford University School of Medicine, Stanford, California, USA. METHODS: Ninety-three eyes had PARK for primary compound myopic astigmatism. Preoperative pupil diameters were measured under scotopic and photopic illuminance conditions. Postoperatively, patients were evaluated at 1, 3, 6, 9, 12, 18, and 24 months. A regression model was performed to evaluate the predictive value of assessing preoperative variables such as pupil diameter on the development of glare and halos, contrast sensitivity, and best spectacle-corrected visual acuity (BSCVA) under scotopic, photopic, and glare conditions. RESULTS: The greater magnitude loss of BSCVA under scotopic conditions in the early postoperative period as well as the slower recovery to preoperative levels in eyes with larger scotopic pupil diameters were not statistically significant (P >.05). An increase in symptoms of glare was related more to the attempted level of spherical equivalent (SE) correction than to the pupil size during the first 12 postoperative months (P <.01). The photoablation dimensions as determined by the attempted level of astigmatic correction may result in decreases in the glare BSCVA up to 12 months after PARK (P =.03). At the 2 year follow-up, pupil diameter under both scotopic and photopic illuminance conditions was not predictive of any of the measured outcomes variables. CONCLUSIONS: An assessment of preoperative pupil size and the attempted level of both SE and astigmatic correction may be useful in identifying patients at risk of developing symptoms or declines in visual performance after PARK. However, follow-up studies are indicated to identify variables predictive of poor visual outcomes following excimer laser refractive surgery.

Adaptation, Ocular↗
PubMed1992

Pupil diameter and the principal ray.

Placement of the surgical zone is critical in refractive procedures that alter a portion of the corneal curve. An improperly centered optical zone may produce glare, decrease best corrected visual acuity, and decrease contrast sensitivity. For proper placement, the new surface should be centered around the line of sight, which is the principal ray from the object of regard that passes through the image of the patient's pupil as projected on the cornea. This point is not necessarily at the geometric center of the cornea and is found by locating the center of the pupil while the patient is maintaining fixation coaxially with the surgeon. However, the pupil does not dilate concentrically and its geometric center moves as the pupil diameter changes. We have found a shift up to 0.7 mm in the geometric center of the pupil as it dilates. Therefore, centration of an ablated or a radial keratotomy zone is most efficiently done when the diameter of the modified corneal optical zone is centered around the line of sight and is superimposed upon the entrance pupil. This will minimize extension of the edge of the large pupil beyond the ablated zone and reduce unwanted secondary optical effects from degrading vision.

Adult↗
PubMed2006

[Influence of intraoperative pupil diameter and nuclear grade due to complications during Aqualase phacoemulsification].

PURPOSE: The aim of this study was to make an evaluation of the frequency of intraoperative complications during Aqualase phacoemulsification and correlate it to different intraoperative pupil diameters and nuclear grades. METHODS: Aqualase phacoemulsification was performed in 23 eyes without retinal or optic disc pathology in 23 unselected patients (15 women and 8 men) who underwent out-patient cataract surgery. Nuclear grade, intraoperative pupil diameters and complications were recorded. The correlation of intraoperative complications with intraoperative pupil diameter and nuclear grade was determined using "Fisher's exact" test. RESULTS: The average age of our patients was 70.3 (+/- 12.5) years, the mean best spectacle-corrected visual acuity (BSCVA) preoperatively was 0.39 (+/- 0.15) and the mean BSCVA postoperatively was 0.79 (+/- 0.13). The mean aqua time was 3.11 s (+/- 1.55 s) with maximum nuclear sclerosis of up to grade 3 (mean nuclear sclerosis 1.9). The aqua time correlated with the nuclear sclerosis (r = 0.90). The mean intraoperative pupil diameter was 7.2 (+/- 0.7) mm. In 2 of 3 patients with an intraoperative pupil diameter of 6 mm, iris touch occurred intraoperatively. There were no other intra- or postoperative complications. The frequency of iris touch was statistically significantly higher for reduced pupil diameters (p = 0.01). The nuclear grade with a maximum of 3 was without statistical significance to iris touch frequency (p > 0.05). CONCLUSIONS: The number of iris traumas is significantly higher when the intraoperative pupil diameter is reduced. The iris should be protected in these cases. A prospective, randomised study should be performed to compare the number of intraoperative complications between ultrasound and Aqualase phacoemulsification.

Aged↗
PubMed2002

Pupil response components: studies in patients with Parinaud's syndrome.

In addition to light flux changes, it is well established that other stimulus attributes such as colour, spatial structure or movement can also cause a transient constriction of the pupil, even when the onset of the stimulus causes a net decrease in light flux level on the retina. Although experimental findings in human subjects with postgeniculate lesions show that the generation of such responses must involve the processing of stimulus attributes in extrastriate areas of the cortex, little is known about the site of integration of cortical signals into the pupillomotor pathway. We have investigated how visual performance and the various components of the pupil response have been affected in subjects with damage to the dorsal midbrain (Parinaud's syndrome). The results show that the probable destruction of the olivary pretectal nucleus and the nucleus of the optic tract has little or no effect on pupil grating or pupil colour responses. The light reflex response, on the other hand, is virtually abolished, with only a small residual component that is similar to the pupil grating response and may not require an afferent projection to the midbrain. These new findings suggest that the site of integration of cortical signals in relation to pupil colour and grating responses and the generation of sleepiness-induced oscillations of the pupil do not rely on the normal functioning of pretectal nuclei that are involved in the light reflex response.

Adult↗
PubMed2001

Pupil diameter and light reaction during cardiac arrest and resuscitation.

OBJECTIVE: Traditionally, both pupil diameter and reaction to light have been examined to confirm the diagnosis of death. In the present study, we investigated quantitative changes in pupil diameter and light reaction for assessing the efficacy of cardiopulmonary resuscitation (CPR) and as a predictor of outcome. DESIGN: Controlled experimental study. SETTING: Animal research laboratory at a university-affiliated research institute. SUBJECTS: Fifteen domestic male pigs weighing between 33 and 40 kg. INTERVENTIONS: Ventricular fibrillation was induced with an alternating current delivered to the right ventricular endocardium. After 7 mins of untreated ventricular fibrillation, chest compression and mechanical ventilation were initiated and maintained for 6 mins. Restoration of spontaneous circulation then was attempted by electrical defibrillation. MEASUREMENTS AND MAIN RESULTS: Spontaneous circulation was reestablished in 9 of 15 animals. Pupils were fully dilated, and pupillary reaction to light was absent in 7 of the 9 resuscitated animals during untreated cardiac arrest. Progressive decreases in pupil diameter were observed together with restoration of light reaction during CPR, in each animal that was successfully resuscitated. When the pupils remained dilated and unreactive after 6 mins of CPR, resuscitation efforts were uniformly unsuccessful. A highly significant linear correlation between coronary perfusion pressure generated during precordial compression and pupil diameter was documented. Both were predictive of outcome. CONCLUSIONS: Dynamic changes of pupil diameter and reactions to light during cardiac arrest and resuscitation were correlated with coronary perfusion pressure, and both predicted the likelihood that spontaneous circulation and cerebral function would be restored.

Animals↗
PubMedDate not supplied

New markers for type A behavior: pupil size and platelet epinephrine.

This study tested the hypothesis that the Type A behavior pattern and its components are associated with increased activity of the sympathetic nervous system. To do this, we employed two new markers of sympathetic tone--pupil size and platelet catecholamine content. Thirty-three healthy males were blindly rated for Type A behavior and verbal stylistic components by Structured Interview. Adrenergic tone to the pupils was assessed from pupil diameter recorded by infrared television pupillometry, and pupil alpha-adrenergic sensitivity was estimated from mydriatic response to ophthalmic phenylephrine. Platelet epinephrine and norepinephrine contents were assayed because these levels are associated with chronic, long-term circulating catecholamine levels. The results showed Type As had consistently larger pupil diameters than Type Bs (p = 0.03, 0.03, and 0.01). There was no difference in pupillary response to phenylephrine instillation between groups. Platelet epinephrine content was greater in Type A subjects (chi 2 = 4.25, p less than 0.04, t = 1.6, p = 0.06). Only the component of explosiveness was modestly associated with resting pupil size, and no components significantly predicted platelet catecholamines. We conclude that the results of these two new markers of autonomic activity, namely, pupil size and platelet epinephrine, suggest that Type A behavior is characterized by increased sympathetic nervous system tone although we cannot rule out the possibility of decreased activity of the parasympathetic nervous system.

Adult↗
PubMed2006

Pupil size and corneal laser surgery.

PURPOSE OF REVIEW: The role of scotopic pupil size as a factor in predicting night vision complaints is controversial. This review summarizes reports in the literature, some that have found and some that have failed to find a correlation with scotopic pupil size and night vision complaints. RECENT FINDINGS: Pupil-measuring devices are discussed along with informed consent issues and reports showing that wavefront aberrations increase with increasing pupil size. A new objective measuring device (Larson) showed a correlation with postoperative starbursts and pupil size and a decrease in starbursts with wavefront-guided treatments compared with conventional excimer laser treatments. Cortical adaptation allows many patients to adapt to their new night vision. Treatment options for those who remain symptomatic include drops to reduce pupil size and wavefront-guided retreatments. SUMMARY: Reports in the literature are conflicting, and refractive surgeons would be wise to inform their patients that large scotopic pupil size is a potential risk factor for night vision complaints. By doing this they will follow the recommendations in recent patient information brochures of both VISX (Santa Clara, California) and Alcon (Orlando, Florida) and on the United States Food and Drug Administration web site.

Cornea↗
PubMed2004

Effects of changing the direction of gravity on sector pupil dilations.

PURPOSE: To study anterior segment aqueous humor kinetics by using sector pupil dilations with different directions of gravity to change the direction of convectional flow in the anterior chamber. METHODS: Sector pupil dilations were elicited using focal applications of phenylephrine at the limbus. To vary the direction of gravity (and hence the direction of convectional flow) relative to the eye, subjects' heads were tilted left side down or right side down with gaze horizontal. Pupil elongation and pupil center displacement were measured as functions of time. RESULTS: Early stages of pupil dilation were dominated by pupil elongation toward the site of drug application. Amplitude of elongation was about the same for all the application points, but center displacement depended on the application point. Later stages of pupil dilation showed an interaction between the site of drug application and the direction of gravity. CONCLUSIONS: The results are interpreted in terms of anterior chamber convectional flow and its interaction with transpupillary aqueous flow and diffusion. Early distribution in the anterior segment of a substance applied to the limbus appears to be determined primarily by local diffusion, whereas later distribution is affected by movement of the drug in convectional and transpupillary flow.

Adult↗
PubMed2006

Dynamic measurement of accommodation and pupil size using the portable Grand Seiko FR-5000 autorefractor.

PURPOSE: The purpose of this study was to evaluate the potential of the portable Grand Seiko FR-5000 autorefractor to allow objective, continuous, open-field measurement of accommodation and pupil size for the investigation of the visual response to real-world environments and changes in the optical components of the eye. METHODS: The FR-5000 projects a pair of infrared horizontal and vertical lines on either side of fixation, analyzing the separation of the bars in the reflected image. The measurement bars were turned on permanently and the video output of the FR-5000 fed into a PC for real-time analysis. The calibration between infrared bar separation and the refractive error was assessed over a range of 10.0 D with a model eye. Tolerance to longitudinal instrument head shift was investigated over a +/-15 mm range and to eye alignment away from the visual axis over eccentricities up to 25.0 degrees . The minimum pupil size for measurement was determined with a model eye. RESULTS: The separation of the measurement bars changed linearly (r2 = 0.99), allowing continuous online analysis of the refractive state at 60 Hz temporal and approximately 0.01 D system resolution with pupils >2 mm. The pupil edge could be analyzed on the diagonal axes at the same rate with a system resolution of approximately 0.05 mm. The measurement of accommodation and pupil size were affected by eccentricity of viewing and instrument focusing inaccuracies. CONCLUSIONS: The small size of the instrument together with its resolution and temporal properties and ability to measure through a 2 mm pupil make it useful for the measurement of dynamic accommodation and pupil responses in confined environments, although good eye alignment is important.

Accommodation, Ocular↗
PubMed1987

The intracellular pupil mechanism and photoreceptor signal: noise ratios in the fly Lucilia cuprina.

The function of the intracellular pupil mechanism is examined by comparing the responses of photoreceptors in normal flies with those from white-eyed flies that lack the pupil. In white-eyed flies the response to an intensity increment of fixed contrast decreases at high background intensities. There is a smaller decrease in noise amplitude so that the signal:noise ratio falls. The intensity dependence of the photoreceptor signal:noise ratio fits a simple model in which activated photopigment molecules compete for 3 X 10(4) transduction units. The signal:noise ratio decreases at high intensities because the transduction units are saturated. This model is supported by a noise analysis, which provides three estimates of the number of events generating photoreceptor responses. In white-eyed flies the event number saturates at high background intensities, suggesting that a maximum of 2 X 10(4) events can be simultaneously active. Wild-type flies do not exhibit saturation effects over the range of intensities studied. The signal:noise ratio rises with intensity to reach a stable asymptote, close to the maximum observed for white-eyed flies. Pupil attenuation is calculated from measurements of signal:noise ratio in white-eyed and wild-type flies. The pupil is progressively activated over a two log unit intensity range and when fully closed attenuates the effective intensity by 99%. The threshold of this pupil effect coincides with the threshold of pupil activation measured optically. We conclude that the intracellular pupil attenuates the light flux to prevent receptor saturation and to extend the range of intensities at which fly photoreceptors operate close to their maximum signal:noise ratio. This upper limit is determined by the number of transduction units generating a cell's response.

Animals↗
PubMed2004

Differences in FM100-Hue test performance related to iris colour may be due to pupil size as well as presumed amounts of macular pigmentation.

BACKGROUND: It has been reported that the differences in macular pigment between Asian and Caucasian eyes might give rise to different performance on the Farnsworth-Munsell 100 Hue test. However, the study did not appear to account adequately for the observation that differences were apparent only in older age groups. It was also acknowledged that other factors, like pupil size and crystalline lens colouration, could influence the result. METHOD: We investigated the performance of the Farnsworth-Munsell 100 Hue test, under standard conditions, by three groups with presumed different macular pigmentation and narrow age range. We also measured pupil size. RESULTS: The group with blue irides (presumed low macular pigmentation) performed significantly better on the colour vision task than the Asian group and the brown-eyed subjects as a whole (presumed higher macular pigmentation). In addition, the difference in pupil size between the blue-eyed group and brown-eyed groups bordered on significance. The difference in pupil size and consequential reduction in retinal illuminance account for a significant proportion of the difference in colour vision performance. In addition, a difference in both pupil size and Farnsworth-Munsell 100 Hue test performance was also observed between males and females that reinforced the importance of pupil size, and not just macular pigment, as a factor in colour vision performance difference between Asian and non-Asian eyes. CONCLUSION: It is concluded that pupil size, not just macular pigment, may have a significant influence on colour vision performance in a young, healthy population.

Adult↗
PubMed1989

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.

Accommodation, Ocular↗
PubMed1978

Edge-light pupil cycle time.

A thin slit-lamp beam illuminating the pupil margin produces clearly visible pupil oscillations. These oscillations can be timed with a stopwatch, thus producing a measurement of the "edge-light" pupil cycle time'. The pupil cycle time is remarkably stable in various testing situations and is repeatable within about +/- 3% over extended periods of time. Expected normal distribution and 95% confidence intervals are given in Table 3. When the iris muscles are normally innervated and responsive, the pupil cycle time is dependent on the speed of nerve conduction and the number and strength of optic nerve impulses. Only 5% of normal persons aged 12 to 50 years are expected to have a pupil cycle time in either eye longer than 954 ms or a difference in pupil cycle time between the two eyes longer than 70 ms.

Adolescent↗
PubMed2006

Variability in pupil size estimation.

BACKGROUND: The clinical estimation of pupil size and reactivity is central to the neurological assessment of patients, particularly those with or at risk of neurological damage. Health care professionals who examine pupils have differing levels of skill and training, yet their recordings are passed along the patient care pathway and can influence care decisions. The aim of this study was to determine if any statistical differences existed in the estimation of pupil size by different groups of health care professionals. METHODS: A total of 102 health care professionals working in the critical care environment were asked to estimate and record the pupil size of a series of 12 artificial eyes with varying pupil diameter and iris colour. All estimations were performed indoors under ambient lighting conditions. RESULTS: Our results established a statistically significant difference between staff groups in the estimation of pupil size. CONCLUSION: The demonstrated variability in pupil size estimation may not be clinically significant. However, it remains desirable to have consistency of measurement throughout the patient care pathway.

Analysis of Variance↗
PubMed1979

Static and kinetic properties of the dolphin pupil.

In dim illumination, adult human pupil area becomes asymptotic at about 51 mm2 whereas the dolphin pupil achieves an area of about 70 mm2 under equivalent conditions. At moderate illumination levels (greater than 100 lx), the dolphin pupil becomes a horizontally oriented ellipse and develops a pronounced central constriction with additional light. The relative relationship between pupil area and illumination copmares closely with published human data. Rates of pupil response to step increments in illumination are very similar for the two species. Although the pupil has been proposed as a mechanism for correction of the dolphins' high aerial myopia, correlation of the laboratory findings on static and kinetic pupil properties with visually controlled aerial behaviors disclosed no special interdependence.

Adaptation, Ocular↗
PubMed2000

Temperature-induced pupil movements in insect superposition eyes.

In this paper, we describe the hitherto largely overlooked effect of temperature on the pupil of insect compound eyes. In the turnip moth Agrotis segetum and in two other nocturnal insects with superposition eyes, the lacewing Euroleon nostras and the codling moth Cydia pomonella, the pupil not only opens and closes with changes in the ambient light level, as expected, but also with changes in temperature in the absence of light. In complete darkness, the pupil of A. segetum responds over a wide range of temperatures, with the pupillary pigments migrating to a light-adapted position when the animal is exposed to either low or high temperatures. At temperatures between 21.0 and 22.7 C, the pigments migrate to the fully dark-adapted position, resulting in an open pupil and maximal eye glow. Pupil closure at high temperatures shows two distinct thresholds: the first at 23.8+/-0.7 C and a second some degrees higher at 25.7+/-1.2 C (means +/- s.d., N=10). Temperatures exceeding the first threshold (the activation temperature, T(a)) initiate a closure of the pupil that is completed when the temperature exceeds the second threshold (the closure temperature, T(c)), which causes rapid and complete migration of pigment to the light-adapted position. All temperatures above T(a) affect the pupil, but only temperatures exceeding T(c) result in complete closure. Temperatures between T(a) and T(c) cause a slow, partial and rather unpredictable closure. The lacewing and the codling moth both show very similar responses to those of A. segetum, suggesting that this response to temperature is widespread in superposition eyes. The possibility that the ambient temperature could be used to pre-adapt the eye to different light intensities is discussed.

Animals↗
PubMed1995

Double-pass measurements of the retinal-image quality with unequal entrance and exit pupil sizes and the reversibility of the eye's optical system.

We have used a modified double-pass apparatus with unequal entrance and exit pupil sizes to measure the optical transfer function in the human eye and have applied the technique to three different problems. First, we confirm that in the eye the double-pass spread function is the cross correlation of the input spread function with the output spread function [J. Opt. Soc. Am. A 12, 195 (1995)]. Consequently, when entrance and exit pupil sizes are equal, phase information is lost from the double-pass images. Second, we show that in double-pass measurements the eye behaves like a reversible optical system. That is, when entrance and exit pupils are equal, the double-pass image results from two passes through an optical system having a transfer function that is the same in both directions. To test for reversibility in the living eye we have used a double-pass apparatus with different exit and entrance pupil sizes (one of them small enough to consider the eye diffraction limited), so that the ingoing and the outgoing transfer functions are different. The measured image quality was unchanged when the pupils were interchanged, i.e., when the first-pass entrance pupil size becomes the second-pass exit pupil size, and vice versa. Third, the technique provides a means for inferring the complete optical transfer function of the eye, including the phase transfer function, and the shape of the point-spread function.

Accommodation, Ocular↗