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At least 379 records · Page 21Linked to original sources
PubMed1985

The relationship between feline pupil size and luminance.

The relationships between luminance and height, width or area of the feline pupil were investigated in awake, normal adult cats whose pupils were photographed over a range of light levels with the aid of electronic flash. The results are compared with previous measurements of pupil width and height in awake animals (Kappauf 1943); and with estimates of pupil width, height and area in lightly-anaesthetised cats (Wilcox and Barlow 1975). The implications of these results for retinal illumination and colour discrimination are discussed.

Age Factors↗
PubMed2004

The effects of pupil size on the multifocal electroretinogram.

This is an investigation of the effect of changing the pupil diameter on the P1 amplitude and latency of the multifocal electroretinogram (mfERG). MfERGs were recorded using a custom built wide field electrophysiological system. An array of 61 empirically scaled hexagons was used to stimulate the visual field. The duration of overall recording period was 8 min, segmented into 16 intervals each lasting 30 s. A combination of mydriatics and miotics were used to pharmacologically alter the pupil size and diameters between 1 and 10 mm were measured. There was a reduction in mfERG P1 amplitude in some cases greater than 50% (mfERG P1 amplitude 53 nV at 8 mm to 25 nV at 1 mm), with a change in pupil diameter of 7 mm. The mfERG P1 latency increased in some cases by as much as 8 ms in the central 40 degrees (mfERG P1 latency 39 ms at 8 mm to 47 ms at 1 mm). These results suggest that pupil size has significant effects on mfERG P1 amplitude and latency.

Electroretinography↗
PubMed1980

Pupil cycle time in optic nerve compression.

We measured pupil cycle time before and after treatment in 11 patients with compressive optic nerve disease. Nine patients had chiasmal tumors and two had optic neuropathy of Grave's disease. Pupil cycle time before treatment was abnormal in at least one eye of all patients and in each case, pupil cycle time improved or worsened in accordance with the response to treatment of the patient's visual acuity and visual fields. This suggests that the pupil cycle time may be used as a simple objective office test for following up patients with impaired optic nerve conduction as the result of optic nerve compression. This information is similar to that gained from visual evoked response and may be used together with other objective clinical data such as disk pallor, nerve fiber loss, and relative afferent pupillary defect.

Adenoma↗
PubMed1983

Dynamic pupillary response controlled by the pupil size effect.

Pupillary escape has been described as an initial contraction followed by a slow redilatation, occurring in response to a step stimulus of low-intensity light. When the initial pupil size is small, the response to the same step stimulus is pupillary capture, a steady and sustained contraction. In this experiment a comparison was made between three modes of controlling pupil size and thereby of regulating the pupillary response: contralateral light background level, ipsilateral light background level, and accommodative level with which there is no change in retinal adaptation. All three level setting modes showed similar results in illustrating the pupil size effect. In addition, an inhibitory effect was found with both ipsilateral and contralateral light backgrounds that is independent of Weber's Law in the contralateral case. Our results lead to the formulation of a binocular model, featuring an internal parameter control whereby a signal dependent on the static pupil size regulates the gains of the parallel phasic and tonic pathways, the former responsive to transient changes of light, and the latter to background levels of light and accommodative levels. Our findings also raise interesting questions concerning the loci of these complex interactions in the simple neuroanatomy of the pupillary pathways.

Humans↗
PubMed1983

Image quality of the human eye for eccentric entrance pupils.

The human eye has a considerable amount of chromatic aberration and a moderate amount of spherical aberration. If a small artificial pupil is placed in front of such optics and moved away from the centre towards the periphery the chromatic aberration will result in lateral colour shifting, and the spherical aberration will cause coma. Starting from available experimental data on the chromatic aberration and the spherical aberration, modulation transfer functions (MTF's) are calculated for central and eccentric positions of small pupils placed in front of the human eye. These calculations may help to separate optical and retinal contributions to the well-known reduction of visual acuity measured with eccentric pupils. It appears that measurements with pupils smaller than 1 mm in monochromatic light can be considered optically as diffraction limited. Changes of visual acuity found in this way must be assigned to the retina.

Humans↗
PubMed1988

The effect of pupil centration and diameter on ocular performance.

The variation in sphero-cylindrical refractive error with position in the human eye pupil is derived from the wavefront error of two subjects. The modulation transfer function is also calculated for 1, 2 and 3 mm pupils decentred 1 and 2 mm nasally and temporally. Whilst decentration causes relatively little difference in the M.T.F. at the smaller pupil size, it can produce marked degradation for the larger pupils which can be of significance in the experimental determination of contrast sensitivity or other visual functions.

Humans↗
PubMed1988

The pupil's response to short wavelength cone stimulation.

Using i.r. pupillometry, we measured the response of the pupil to tritanopic metamers alternating at 0.94 Hz. These are lights that differentially stimulate only the short wavelength (S) sensitive cones. We find a response at the alternation frequency for 5 of 7 observers. This shows, for the 5 observers, that S cone signals can influence pupil size, probably via the traditional retinotectal light reflex pathway. Changing the radiance of just one of the alternating pair of lights causes the two lights to differ in their total M + L cone stimulation. The pupil's response to this imbalance can antagonize its response to S cone stimulation. By this procedure we find that imbalances in M + L cone stimulation of less than 0.3 log10 unit offset the pupil's response to S cone stimulation of more than 0.8 log10 unit. This suggests that afferent pupillary signals from S cones are weak relative to those from M + L cones.

Color Perception↗
PubMed1990

Evaluation of pupil constriction and dilation from cycling measurements.

Pupil cycling was produced using an electronic circuit so that the retina was illuminated in Maxwellian view only when pupil area exceeded an adjustable area threshold, Aref. The maximum (Amax) and minimum (Amin) amplitude of the oscillations varied linearly with Aref. These observations are described by a delay-differential equation. The Aref-dependent changes in Amax, Amin were used, respectively, to quantitate dilation and constriction. A comparison of the predicted and observed period of pupil cycling suggests that the latency times for light onset and offset are the same. Measurements of Amax, Amin provide a method for determining the average pupil light response.

Adult↗
PubMed2004

The effect of daily use of brimonidine tartrate on the dark-adapted pupil diameter.

PURPOSE: To investigate the effect of daily brimonidine tartrate 0.15% on the dark-adapted pupil diameter. DESIGN: Observational case series. METHOD: Ten normal volunteers administered brimonidine to their right eyes once daily. Four to six hours later, infrared pupil photographs were taken after dark adaptation. Measurements were performed at baseline; on treatment days 1, 5, 11, and 18; and on washout days 1 and 2. RESULTS: One subject had no response. The nine responding subjects showed an average maximum antimydriatic effect of -1.63 mm (range, -0.57 mm--2.30 mm); all subjects experienced tachyphylaxis. Five subjects showed rebound mydriasis (mean maximum rebound +0.87 mm larger than baseline; range 0.50 mm-1.22 mm). The untreated pupil also responded, showing antimydriasis (two subjects), rebound mydriasis (two subjects), or paradoxical direct mydriasis (one subject). CONCLUSIONS: Once-daily use of brimonidine tartrate to prevent dark-induced pupil dilation can lead to tachyphylaxis and rebound mydriasis.

Adolescent↗
PubMed2004

Pupil staging and EEG measurement of sleepiness.

The goal of this multi-method study was to examine the validity (accuracy) of the pupillometric Alertness Level Test (ALT) as a physiologic measure of sleepiness. The study used a pooled-time series-correlation design with 16 untreated narcolepsy (8 F, 8 M), 16 untreated obstructive sleep apnea (OSA) (7 F, 9 M) and 16 healthy control (8 F, 8 M) subjects. Participants underwent EEG/polysomnography testing using standard Multiple Sleep Latency Test electrode placement concurrent with the 15 min pupillometric ALT. EEG data were examined to determine if theta power (4-7 Hz) increased during 2-s periods of proportional pupil size decreases (pupil Stage 1, 95% or more of maximal pupil size to Stage 4, 65-74% of maximal size). Printed EEG records also were visually scored. Self-report sleepiness measures included the Pittsburgh Sleep Quality Index, the Profile of Mood States and the Epworth Sleepiness Scale. Within subject groups, theta power ratios significantly increased across pupil stages for the sleep disorder groups but not for controls (theta activity increased 42% for narcoleptic and 36% for OSA subjects). Between subject groups, the amount of theta activity was significantly greater for narcoleptic and OSA subjects than that for controls. Visual EEG scoring and self-report measures were usually consistent with objective findings. The ALT is convenient, easily repeatable and less technically demanding than EEG sleepiness measures, and it deserves more comprehensive testing as a valid measure of sleepiness.

Adult↗
PubMed2004

Day to day variability of the dark-adapted pupil diameter.

PURPOSE: To determine the individual variability of the dark-adapted pupil diameter over 2 testing sessions using a standardized dark-adaptation protocol. SETTING: Texas Tech University Health Sciences Center, Lubbock, Texas, USA. METHODS: In this prospective observational cohort study, 40 volunteers with no history of ocular disease, surgery, or injury other than requirement for refractive correction were included. The right eye was tested. A standardized dark-adaptation protocol was used that controlled for accommodation and patient alertness. Infrared, still digital photographs were taken after 5 and 10 minutes of dark adaptation and analyzed independently by 2 investigators using digital-image software. Two test sessions were performed 1 to 7 days apart. Lifestyle factors such as sleep, diet, and exercise were not controlled. RESULTS: The mean subject age was 31.5 years (range 20 to 49 years). There were 20 men; 27 subjects wore correction for myopia, and 13 wore no correction. The mean interval between test sessions was 2 days (range 1 to 7 days). The mean difference and 95% confidence intervals for pupil diameter difference between sessions were as follows: 5-minute readings, +0.032 mm (-0.030 to +0.094); 10-minute readings, -0.006 mm (-0.059 to +0.047); mean of 5- and 10-minute readings, +0.013 mm (-0.038 to +0.064). Using the paired t test, the pupil diameter did not differ significantly between sessions in 5-minute dark adaptation (P =.2980), 10-minute dark adaptation (P =.8263), or the mean (P =.6049). CONCLUSION: Using a consistent dark-adaptation protocol that controlled for alertness, individuals aged 20 to 49 years showed no significant variation in dark-adapted pupil diameter when tested twice in 1 week.

Accommodation, Ocular↗
PubMed2004

Correlation of infrared pupillometers and CCD-camera imaging from aberrometry and videokeratography for determining scotopic pupil size.

PURPOSE: To compare 2 infrared pupillometers with a videokeratographer and 2 aberrometers for the determination of scotopic pupil size. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. METHODS: The pupil diameter was measured in 100 eyes of 51 patients after 2 minutes of dark adaptation using the following devices: digital infrared pupillometer (Procyon Instruments Ltd.), handheld infrared pupillometer (Colvard) (Oasis Medical), Zywave aberrometer (Bausch & Lomb), Wasca aberrometer (Asclepion-Meditec-Zeiss), and Orbscan II topography system (Bausch & Lomb Surgical). Measurements taken with the Procyon pupillometer were considered reference values for comparison with the other devices. Statistical evaluation was performed using the Bland-Altmann method for comparison of measurement techniques. RESULTS: The mean pupil size was 6.10 mm +/- 0.86 (SD) with the Procyon pupillometer, 5.68 +/- 1.07 mm with the Colvard pupillometer, 5.91 +/- 1.01 mm with the Zywave aberrometer with the fixating target turned off, 5.09 +/- 1.14 mm with the Zywave aberrometer with the fixating target turned on, 5.59 +/- 0.99 mm with the Wasca aberrometer, and 3.75 +/- 0.67 mm with the Orbscan topographer. The limits of agreement were smallest for measurements between Procyon and Colvard and largest for measurements between Procyon and Orbscan. The sign test revealed statistically significant differences for all devices compared with the Procyon pupillometer (P<.001 in all cases) except the Zywave aberrometer with the fixating target turned off (P=.13). CONCLUSIONS: The Zywave wavefront sensor with the fixating target turned off using the study settings and light conditions provided measurements of scotopic pupil diameter that were closest to the reference values (Procyon). With the other devices (Colvard pupillometer, Zywave aberrometer with the fixating target switched on, Wasca aberrometer, and Orbscan topographer), the difference was statistically significant.

Adult↗
PubMed2005

Pupil response to tropicamide following laser in situ keratomileusis.

PURPOSE: To investigate the effect of corneal thinning after laser in situ keratomileusis (LASIK) on the corneal penetration of topical eye medication. SETTING: Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA. METHODS: Laser in situ keratomileusis surgery was performed in 19 eyes of 10 patients enrolled in this prospective study. Measurements were made before surgery and 3 months postoperatively. After instillation of tropicamide 1%, the change in pupil size over time was measured with a Colvard pupillometer. Central corneal thickness (CCT) was measured with ultrasonic pachymetry before and 3 months after LASIK. The corneal epithelial condition was also examined by fluorescein dye staining. RESULTS: The mean CCT decreased significantly from 564 microm +/- 33 (SD) before LASIK surgery to 514 +/- 48 microm 3 months postoperatively (P<.0001). Pupil diameter 10, 15, and 20 minutes after tropicamide 1% instillation was significantly larger 3 months after surgery than preoperatively (P=.0083, P=.0043, and P=.0144, respectively). The mean time to reach a pupil diameter of 6.0 mm decreased significantly from 14.4 +/- 4.3 minutes in preoperative eyes to 11.5 +/- 2.3 minutes in postoperative eyes (P=.0281). Mild punctate corneal epithelial staining (fewer than 5 spots) were observed in 4 eyes at the 3-month postoperative examination. CONCLUSIONS: Pupil dilation after tropicamide 1% instillation was significantly faster after LASIK surgery. Corneal thinning that resulted from LASIK enhanced corneal penetration of tropicamide 1%.

Adult↗
PubMed2006

Comparative higher-order aberration measurement of the LADARWave and Visx WaveScan aberrometers at varying pupil sizes and after pharmacologic dilation and cycloplegia.

PURPOSE: To compare higher-order aberration (HOA) measurements of LADARWave and Visx WaveScan aberrometers, to test the validity of the peripheral wavefront data, and to evaluate the effect of pharmacologic dilation and mild cycloplegia. METHODS: Thirty-three myopic eyes of 17 volunteers were enrolled and had the ocular HOAs measured and analyzed with varying pupil diameters (PD) controlled by a tunable light intensity source and after instillation of tropicamide 1% and phenylephrine 2.5%. RESULTS: Higher-order aberrations increased with PD and optical zone (OZ), especially an OZ between 6.0 mm and 6.5 mm. Spherical aberration increased the most, followed by coma, then trefoil and secondary astigmatism. Measurement differences were observed between LADARWave and WaveScan at an OZ of 6.0 mm, although measurement correlations between the 2 machines were high. In the case of the WaveScan, when PD = OZ (6.0 mm), the spherical aberration and, to a less extent, the coma data differed from those obtained with larger PDs and the same OZ. In the case of the LADARWave, at an OZ of 6.0 mm, the HOAs measured in eyes with physiologic pupils were similar to those in pharmacologically dilated pupils when the physiologic pupil center was taken as the reference. CONCLUSIONS: There were detectable measurement differences between LADARWave and Visx WaveScan. Ensuring that the PD is at least 0.5 mm larger than the desired OZ is very important. Dilation and mild cycloplegia did not clinically affect the wave measurement magnitude or pattern.

Adult↗
PubMed2004

A simple pupil-independent method for recording eye movements in rodents using video.

Previous techniques using video to acquire torsional eye-movement recordings in humans have needed to control confounding effects associated with dilation of the pupil. A new pupil-independent, three-dimensional eye-movement recording method was developed to overcome the reliance on tracking the pupil by interpolating between two artificial landmarks placed on the eye. This technique reliably quantified torsional changes in angular eye position at variable amplitudes of horizontal and vertical excursion over at least a 20 degrees range. Application of this system to rodents naturally lacking a clearly defined pupil allows behavioral researchers to obtain torsion in addition to horizontal and vertical changes in angular eye position.

Algorithms↗
PubMed2000

Tonic pupil associated with congenital neuroblastoma, Hirschsprung disease, and central hypoventilation syndrome.

PURPOSE: To report the association of tonic pupil, congenital neuroblastoma, Hirschsprung disease, and central hypoventilation syndrome. METHODS: Case reports. RESULTS: Two infants with central hypoventilation syndrome and Hirschsprung disease were evaluated for dilated, nonreactive pupils present since birth. In both cases, pharmacologic testing with dilute pilocarpine confirmed denervation supersensitivity consistent with tonic pupil. The diagnosis of congenital neuroblastoma was subsequently established in both infants. CONCLUSIONS: The close association of these conditions in these two young children supports the concept of a common neural crest abnormality being present. A careful systemic evaluation to rule out congenital neuroblastoma should be performed in any young child who presents with tonic pupil in the setting of central hypoventilation syndrome and Hirschsprung disease.

Adrenal Gland Neoplasms↗
PubMed2001

Asymmetric pigment dispersion in a patient with the unilateral Adie pupil.

PURPOSE: Pigmentary glaucoma is a bilateral disorder. When it occurs asymmetrically or unilaterally, a cause should be sought because it may help us to understand the pathophysiology of this condition better. We describe a patient with unilateral pigmentary glaucoma and the Adie pupil in the same eye and discuss the possible role of the Adie pupil in the development of the pigmentary glaucoma. METHODS: A case report. A 37-year-old woman presented with asymmetric pigment dispersion resulting in pigmentary glaucoma in the right eye and an unilateral Adie pupil in the same eye. RESULTS: We believe that the dilated Adie pupil in the right eye might have resulted in a decreased amount of relative pupillary block. This, then, might have led to an increased contact between the posterior iris and the zonules, resulting in greater pigment dispersion and trabecular obstruction in the right eye. CONCLUSION: It has been proposed that the pigment is liberated from the iris pigment epithelium because of the mechanical rubbing of the posterior iris against the anterior zonular packets. Our case supports this proposed mechanism of pigment release.

Adult↗
PubMed2003

Tonic pupil and sarcoidosis.

PURPOSE: To present a case of tonic pupil associated with enhancement in the region of the ciliary ganglion on magnetic resonance imaging in a patient with sarcoidosis. DESIGN: Observational case report. METHODS: A 52-year-old woman with sarcoidosis had a right pupil exhibiting sectoral palsy to light and light-near dissociation. RESULTS: Topical administration of 0.1% pilocarpine demonstrated supersensitivity of the right pupillary sphincter muscle. Magnetic resonance imaging (MRI) with contrast revealed enhancement in the region of the right ciliary ganglion. CONCLUSIONS: Tonic pupil may be a manifestation of sarcoidosis, and in such cases, MRI may show enhancement at the level of the ciliary ganglion. Sarcoidosis should be included in the differential diagnosis of tonic pupil.

Blepharoptosis↗