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Results for “Reflex, Pupillary”

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At least 127 records · Page 7Linked to original sources
PubMed1982

Retinal sensitivity measured by the pupillary light reflex in RCS and albino rats.

The effects of retinal degeneration on the sensitivity of the retina were studied in the Royal College of Surgeons (RCS) rat by measuring the light reflex of the pupil in response to ganzfeld (full field) flashes. Light reflex thresholds were measured for animals from 32 to 683 days of age, and an age-related decrease in sensitivity of 5.2 log units (maximum) was measured. In contrast, thresholds for non-dystrophic albino controls increased only slightly during a comparable period. RCS rat thresholds increased more for short wavelength light than for long wavelength light. The end result was an altered action spectrum of the light reflex which largely, but not exclusively, reflected cone function. Even in cases of advanced degeneration the light reflex thresholds we measured showed significant input from rods. Pupiliary dark adaptation measured following ganzfeld bleaches (10%) with test stimuli of two different wavelengths revealed two mechanisms; a photopic mechanism (gamma max = 520) determined thresholds early in dark adaptation, but later a scotopic mechanism (gamma max = 500) participated in the light reflex.

Aging↗
PubMed1996

Effect of locally applied prazosin on the kinetics of the pupillary light reflex.

The effect of locally applied prazosin on pupillometric measures was studied in healthy volunteers, in an attempt to identify the role of alpha 1-adrenoceptors in the recovery time of the light reflex. Prazosin antagonized the mydriatic effect of phenylephrine, but did not alter that of tropicamide. Miotic responses to a range of light stimuli were measured under ambient temperature conditions of 22 degrees C and 40 degrees C. The 40 degrees C condition was associated with shorter recovery times of the light reflex; prazosin increased the recovery time under both temperature conditions. Response amplitude was not affected by the temperature condition or prazosin. The results are consistent with the hypothesis that sympathetic neuromuscular transmission is involved in the redilatation of the pupil following a miotic response to light stimulation.

Adolescent↗
PubMed1990

Attenuation of the pupillary light reflex in anxious patients.

1. The miotic responses evoked by brief light stimuli were compared between a group of 10 patients suffering from generalized anxiety disorder and 10 age- and sex-matched healthy control subjects. 2. Resting pupil diameter in the dark did not differ significantly between the two groups. 3. In both groups, the amplitude of the light reflex was linearly related to the logarithm of the intensity of the light stimulus; responses in the anxious patient group had consistently lower amplitudes than those in the control group. 4. In both groups, the time taken for 75% recovery of the baseline pupil diameter following a light stimulus was linearly related to the logarithm of the light intensity; the 75% recovery times did not differ significantly between the two groups. 5. It is suggested that these results are consistent with a greater supranuclear inhibition of the parasympathetic oculomotor reflex arc in the anxious patients.

Adult↗
PubMed1991

Effects of clonidine and yohimbine on the pupillary light reflex and carbachol-evoked sweating in healthy volunteers.

The effects of single doses of clonidine hydrochloride (200 micrograms), yohimbine hydrochloride (22 mg), a combination of the two treatments, and placebo, on some autonomic functions were studied in healthy volunteers using a double-blind crossover design. Clonidine prolonged the recovery time of the light reflex, lowered systolic blood pressure and reduced subjectively rated alertness; these effects were reversed by yohimbine. Responsiveness of sweat glands to carbachol was not affected by the treatments.

Adult↗
PubMed1992

Effect of high ambient temperature on the kinetics of the pupillary light reflex in healthy volunteers.

Miotic responses to brief light stimuli were studied in healthy volunteers under two ambient temperature conditions, 22 degrees C and 40 degrees C. The latency and amplitude of the light reflex did not differ between the two conditions, but the recovery time of the reflex was significantly shorter under the 40 degrees C condition than under the 22 degrees C condition. The results are consistent with the hypothesis that exposure to high ambient temperature results in an increased sympathetic drive to the iris dilator muscle but does not influence the parasympathetic light reflex.

Adult↗
PubMed2005

The pupillary light reflex in migraine.

The literature suggests that there may be pupil size and response abnormalities in migraine headache sufferers. We used an infra-red pupillometer to measure dynamic pupil responses to light in 20 migraine sufferers (during non-headache periods) and 16 non-migraine age and gender matched controls. There was a significant increase in the absolute inter-ocular difference of the latency of the pupil light response in the migraine group compared with the controls (0.062 s vs 0.025 s, p = 0.014). There was also a significant correlation between anisocoria and lateralisation of headache such that migraine sufferers with a habitual head pain side have more anisocoria (r = 0.59, p < 0.01), but this was not related to headache laterality. The pupil changes were not correlated with the interval since the last migraine headache, the severity of migraine headache or the number of migraine headaches per annum. We conclude that subtle sympathetic and parasympathetic pupil abnormalities persist in the inter-ictal phase of migraine.

Adult↗
PubMed1989

[Age changes in pupillary light reflex. A demonstration by means of a pupillometer].

A new binocular infrared video-pupillograph (C-2515, Hamamatsu Photonics) with a solid state vidicon tube was developed. Various pupil parameters were instantaneously analyzed by a built-in computer system. The equipment also enabled storage of the data on diskettes. A light reflex, induced by a photic stimulus with a duration of 250 msec (intensity: 3,000 troland) was studied. Several parameters of the light reflex were analyzed. These were: pupil area, change in the area of light stimulus, rate of constriction, latency time, and dilatation time at 63% of the amplitude. A total of 160 subjects (320 eyes) was studied. The ages ranged from 5 to 84 years, and subjects were placed in appropriate ten-year age groups (e.g., 0-9 years, 10-19, 20-29, 30-39, etc.). Ten males and 10 females were included in each group. The light reflex was studied in both eyes. The pupil area reduced as the age advanced, with negative correlation. The pupil area in females over 50 years showed a steeper reduction in size, possibly due to hormonal influences. The latency time at 20 years old was the shortest. In subjects below 10 and over 60 years, the latency time was significantly prolonged when compared with the other age groups. The ratio of the velocity of constriction against the velocity of dilatation was calculated and a negative correlation was seen. This may indicate that there are sympathetic influences related to aging and pupil dynamics. The results revealed that an examination of the light reflex by this new pupillography expressed the precise influence of aging on the pupil.

Adolescent↗