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The trigeminal pupillary reflex as a model of vegetative-nociceptive interaction: physiological and clinical aspects.

The study of pupil response to stimuli applied at the corneal level is particularly interesting for the study of integrative sensory-vegetative functions in both physiological and clinical research. In the present study we tried to evaluate and describe pupil response to quantified corneal stimuli in 7 healthy subjects by means of a binocular TV pupillometric device. The pupil response to corneal stimuli was bilateral, direct and consensual. It was characterized by a biphasic progression with an initial response in mydriasis and a later miotic component which was smaller, slower and of longer duration. A direct correlation was observed between the intensity of the stimulus applied and the extent of the mydriasis and between the intensity of the stimulus at the corneal level and the length of the mydriatic response.

Adult↗
PubMed1992

The trigemino-pupillary reflex: a model of sensory-vegetative integration.

Trigeminal stimulation can induce pupillary changes. In vivo and in vitro studies have demonstrated that electrical impulses applied at the trigeminal level can provoke a miotic response, whose nature has been ascribed to the anti-dromic release of neuropeptides (substance P in particular). In order to better define the pupil response to trigeminal stimulation, we investigated the human pupil response to quantified (painless and painful) corneal stimuli by means of a combined (neurophysiological and pharmacological) technique. The response to corneal stimulation was bilateral, direct and consensual. It had a biphasic progression with an initial mydriasis (which directly correlated with the stimulus intensity), followed by a miotic phase. The mydriatic phase disappeared after thymoxamine application, while homatropine pre-treatment prevented occurrence of the miotic phase. The data obtained indicate that the pupillary response to corneal stimulation (trigemino-pupillary reflex) is a multisynaptic reflex with an afferent branch involving the trigeminal system, and an afferent branch involving both the sympathetic and the parasympathetic system. Other pathways, such as the SP-mediated release of acetylcholine, cannot be excluded. Thus the reflex appears to be a potentially useful tool for investigating pain/vegetative interactions in various clinical conditions. In turn, the description of its changes in pathologies characterized by a sympathetic/parasympathetic deficit or by a SP-ergic imbalance will allow us to better describe its inner mechanisms.

Adult↗
PubMed1978

[Pupillary reflex dynamics studied with infrared pupillography].

With a modified method of infrared pupillography--especially developed for the use in clinical neurological routine diagnosis--the time course of the direct phasic pupillary light reflex in man was investigated under physiological and pathological conditions. The described method allows a high resolution of the time course of the light reflex and is superior to kinematographic as well as video-methods described so far. Normally the physiological time parameters are bilaterally symmetrical, also in cases of so-called physiological anisocoria. On the other hand in pathological anisocorias of various etiology pronounced side-differences and abnormal time parameters can be found. Also in cases of isocoria with clinically no abnormal findings of pupillomotor response pathological side-differences can be determined by infrared pupillography. Disturbances of the afferent arc, of the efferent arc and of combination of those as well as pupillary abnormalities to be located in the midbrain area, can be exactly analyzed and documented. Furthermore the method allows an objective documentation of the course in cases of dysfunction of the autonomic nervous system, like in intoxications, or to monitor drug-induced therapeutical measurements. The investigations and findings indicate that infrared pupillography, an objective method for analyzing the dynamics of the pupillary light reflex, is suitable for clinical neurological routing diagnosis.

Adult↗
PubMed1978

The neuronal pathway subserving the pupillary light reflex.

The pupillary light reflex was investigated using electrical stimulation along the pathway and recording in the short ciliary nerves. The discharge of single units in the ciliary ganglion was compared during diffuse light stimuli and electrical stimuli. It was concluded that the early reflex discharge in the short ciliary nerves following electrical stimulation on the optic tract is due to excitation of fibres active during the pupillary light reflex. The light reflex is conveyed by slow (less than 10 m/sec) optic tract fibres which synapase in the medial part of the pretectal area. In turn, pretectal neurones with conduction velocities of about 6 m/sec pass to the Edinger-Westphal complex from which the preganglionic 'pupilloconstrictor' neurones originate. Latency measurements show that there are synapses in the pretectal region and the Edinger-Westphal nucleus. The amplitude of the 'pupilloconstrictor' responses in the short ciliary nerves can be used as a measure of the excitability in the pathway of the pupillary light reflex under various conditions, e.g. following conditioning stimuli of other interacting pathways. In addition to the 'pupilloconstrictor' response there is also another short-latency discharge in the short ciliary nerves following stimulation of the posterior commissure and the Edinger-Westphal nucleus. That discharge is presumably due to activation of fibres which cause accommodation of the lens.

Animals↗
PubMed1991

Isoflurane, but not mild hypothermia, depresses the human pupillary light reflex.

The pupillary light reflex is often evaluated in the perioperative period as a measure of cranial nerve and midbrain integrity. Although surgical concentrations of some anesthetic agents and severe hypothermia qualitatively alter the light reflex, confounding factors frequently present during postanesthetic recovery have not been specifically quantified. We therefore studied 12 volunteers to determine the effects of residual isoflurane concentrations and typical (mild) hypothermia on the human pupillary light reflex. Young, healthy volunteers were assigned to one of three treatments: 1) normothermic isoflurane-oxygen anesthesia; 2) isoflurane-oxygen anesthesia with 2.2 +/- 0.5 degree C central hypothermia; and 3) central hypothermia (1.6 +/- 0.3 degree C) without anesthesia, induced by internal jugular infusion of iced lactated Ringer's solution. In normothermic anesthetized volunteers, the amplitude of the light reflex was depressed 80-90% at end-tidal concentrations greater than 0.5% isoflurane: reflex (percent of control) = 14 - 67.log (percent isoflurane); r = -0.92. In the mildly hypothermic anesthetized volunteers, pupillary responses were not statistically different from those in anesthetized normothermic volunteers: reflex (percent of control) = 16 - 62.log (percent isoflurane); r = -0.97. Hypothermia alone did not alter the magnitude of the light reflex. Our data suggest that mild hypothermia does not depress the light reflex but that isoflurane reversibly depresses the light reflex in a dose-related manner.

Adult↗
PubMed1979

Neuroticism and the effect of stress on the pupillary light reflex.

The pupillary light reflex was recorded under control, stress and fatigue conditions for 30 subjects equally divided into groups low, moderate, and high in Neuroticism. The effects of stress were distinguished by a decrease in both latency and extent of pupillary constriction during the initial light stimulation trials, as well as by a greater magnitude of redilation. Latency to maximum constriction and extent of constriction and redilation progressively decreased during the fatigue condition. No differences between Neuroticism groups were observed although it was noted that Neuroticism was negatively correlated with magnitude of redilation during the post-stress condition.

Humans↗
PubMed1991

The cause of increased pupillary light reflex latencies in diabetic patients: the relationship between pupillary light reflex and visual evoked potential latencies.

In 42 diabetic patients the relationship between the latency of the pupillary light reflex and the pattern reversal visual evoked potential (P100) was examined. Fifty-five percent of diabetic patients had pupillary light reflex latencies above the normal range. In 19% the visual evoked potentials were prolonged when compared to the normal range. Latencies of pupillary light reflexes and VEPs showed no correlation. There was a minimal correlation between the presence of retinopathy and prolongation of both the pupillary light reflex and the visual evoked response latency (kappa coefficients respectively: 0.31, P less than 0.01 and 0.36, P less than 0.02). The presence of an increased pupillary light reflex latency was positively correlated with a reduced respiratory sinus arrhythmia (kappa coefficient: 0.58, P less than 0.0001). Increased VEP latencies showed no correlation with signs of cardiovascular autonomic neuropathy. We conclude that the afferent optic pathway can be affected in diabetic patients. However, prolongation of pupillary light reflex latency in diabetic patients is primarily due to an efferent pupillary defect and represents parasympathetic dysfunction.

Adult↗
PubMed1992

The pupillary light reflex. 2. Prevalence of pupillary autonomic neuropathy in diabetics using age-dependent and age-independent pupillary parameters.

Seventy-seven diabetics with a duration of the disease ranging from 2 to 55 years (average 18.5 years) were studied with infrared videopupillometry. The prevalence of diabetic autonomic neuropathy at the pupillary control system (pANP) was studied comparatively using several pupillary tests. The average prevalence using age-dependent parameters was 30.2% [maximal pupillary area: 22.1%, maximal contraction velocity: 24.7%, contraction velocity at 1 s (CV1): 28.6%, and dilation velocity at 6 s (DV6): 45.5%]. Comparing these percentages to prevalences of other diabetic late complications, e.g. retinopathy (49.4%), DV6 seems to be good for the diagnosis of pANP. If CV1 and DV6 are expressed in percent of the maximal pupillary area (CV1% and DV6%), they become age-independent. The average CV1% and DV6% of diabetics differ highly significantly from those of normals (CV1%: 58.6 +/- 14.5 vs. 64.1 +/- 6.4%, 2 p less than 0.005, and DV6%: 6.0 +/- 2.9 vs. 7.3 +/- 1.1%, 2 p less than 0.001). The average prevalence of pANP using these age-independent parameters was 25.4%. These data suggest that the prevalence of pANP, especially disorders of pupillary dilation (DV6), is high in long-standing diabetes. Furthermore, CV1% and DV6% have proved to be valid parameters in finding differences in the light reflex in non-age-matched study groups.

Adolescent↗
PubMed1977

The cerebellar control of the pupillary light reflex in the cat.

The effect of cerebellar lesions upon the pupillary light reflex was examined in anesthetized cats. The pupillary response elicited by a step and sinusoidally modulated light stimulus was used. In acute cerebellectomized cats, the high frequency cutoff of the frequency response of the pupillary reflex was moved to a lower level after cerebellar lesions. Selective lesions were made in the deep cerebellar nuclei and the frequency responses of the pupillary reflex were compared. The fastigial lesions produced the most prominent change in the frequency responses. Electrical stimulation of the deep cerebellar nuclei, especially the fastigial nuclei, induced pupillary dilatation. Thus the cerebellum appears to participate in the control of the pupillary light reflex by improving the frequency responses of the pupil so that it can follow changing light stimuli better, and this control is exerted via the bilateral fastigial nuclei.

Animals↗