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At least 505 records · Page 28Linked to original sources
PubMed1985

Systems model for pupil size effect. II. Feedback model.

The human pupillary control system has been the subject of interest to biologists and engineers as an example of a sensorimotor reflex which can be embedded in a control system paradigm. We present a nonlinear feedback model whose compact structure allows us to hypothesize possible physiological mechanisms which generate the proper behavior of the pupil system. The important pupil responses, including pupil size effect, asymmetry, and response the high-frequency stimuli, are defined. This model was simulated on a digital computer and comparisons to the paradigm experimental responses were performed, demonstrating a fit to each of the observed conditions. Improvements on previous models are discussed.

Feedback↗
PubMed1975

[The effect of repeated adrenaline application on intraocular pressure and pupil in the rabbit (author's transl)].

The effect of single and repeated topical application of adrenaline on the intraocular pressure and pupil in the rabbit eye was studied using a 2% adrenaline borate and a commercial preparation of 2% adrenaline hydrochloride. On the first day, the hydrochloride gave a more pronounced pressure reduction and pupil diladation than the borate. This was found to be due to the benzalkonium chloride in the chloride preparation causing a better permeability of the adrenaline into the eye. From the second to the fifth day of adrenaline treatment a marked pressure decrease was found from the previous application of the day before. The following adrenaline application gave a hypertensive phase of intraocular pressure lasting two or three hours and a subsequent hypotensive phase lasting more than 24 hrs. The pupil diladation on the second and following days of treatment was not essentially different from the first day considering the observation period of two hours. The hypertensive phase could not be influenced by intravenous or intramuscular propranolol, however, the topical application of propranolol inhibited it completely. Some aspects of adrenergic regulation of the intraocular pressure are discussed.

Animals↗
PubMed1992

Tonic pupil, areflexia, and segmental anhidrosis: two additional cases of Ross syndrome and review of the literature.

Two patients are described with the triad of tonic pupil, hyporeflexia and segmental anhidrosis (Ross syndrome). Only 18 cases of this syndrome have been reported in the literature so far. While tonic pupil and reduced sweating can be attributed to the affection of postganglionic cholinergic parasympathetic and sympathetic fibres projecting to the iris and sweat glands, respectively, the pathogenesis of diminished or lost tendon jerks remains obscure. To identify the characteristic clinical features, the previous cases of Ross syndrome are reviewed. Recent evidence of subclinical disturbances of sweating in most patients with Adie's syndrome, i.e. tonic pupil and areflexia, casts doubt on the nosological concept of Ross syndrome as a distinct clinical entity.

Adult↗
PubMed1978

[The effect of the pupil as aperture and field stop on the various components of the human electroretinogram (author's transl)].

The electroretinogram (ERG) was recorded in 10 normal subjects under scotopic and photopic conditions with the pupil of one eye constricted and that of the other eye dilated. The human iris, being displaced from the nodal point of the eye, acts not only as an aperture, regulating the retinal illumination, but also as a field stop, limiting the visual angle, especially for large object fields, as in Ganzfeld illumination. This double effect of a constricted pupil clearly influences the Ganzfeld ERG, not only shifting the intensity response functions to higher luminances but also diminishing the maximal responses. Control experiments with smaller test fields, which are less affected by the pupillary field-stop properties, reveal no diminution of the scotopic b-wave amplitudes. Implicit time functions, being nearly independent of the number of receptors stimulated, can be matched by taking into account the pupillary diameter and calculating the actual retinal illumination (Troland). Amplitudes, being highly affected by a decrease of responding neurons due to the angle-limiting field-stop character of the pupil, cannot be matched with regard to the pupillary diameter. This effect is most noticeable in Ganzfeld illumination for the scotopic b-wave, generated mainly by neurons of the peripheral retina, and has less effect on the photopic responses that are generated more centrally.

Adaptation, Ocular↗
PubMed2003

[Atypical tonic pupil as a complication of chickenpox infection].

BACKGROUND: Pupillary disorders following varicella infections are rare and few cases have been reported which were only partially pharmacologically tested. MATERIALS AND METHODS: A 5-year-old boy presented with a left-sided dilated and unreactive pupil, 3 months before he had suffered from chickenpox and in the course of the acute disease developed anterior uveitis which was treated with local prednisone and mydriatics. The pupil remained dilated despite discontinued medication, light reaction was absent and accommodation was impaired. Pilocarpine supersensitivity was an indication against a lesion of the sphincter muscle and reduced response to cholinesterase inhibitors (physostigmine) pointed towards a postganglionic lesion. CONCLUSIONS: It is probable that a varicella virus infection of the short ciliary nerves and the ciliary ganglion caused anterior uveitis and a postganglionic parasympathetic nerve lesion, clinically presenting as a tonic pupil. According to cases previously reported an irreversible nerve lesion has to be assumed.

Anti-Inflammatory Agents↗
PubMed2003

[Impairment of safety in navigation caused by alcohol: pupillography and measurement of pupil movements].

OBJECTIVE: To evaluate data in an interdisciplinary project (ophthalmology, forensic medicine, internal medicine, psychology,and nautical science) in order to identify critical blood alcohol limits in sea navigation. METHODS: A sea traffic simulator was employed for realistic nautical demands on 21 professional experienced skippers under sober and alcoholized conditions (target blood alcohol concentration: 1.0 per thousand ). After simulated navigation, pupil light reflex, spontaneous pupil movements,nystagmus,and saccades were evaluated by pupillography. Modification of the pupillograph enabled us also to measure optokinetic nystagmus. RESULTS: Evaluation of the pupil light reflex revealed obvious changes in the extent of relative contraction and in redilatation time under the influence of alcohol. Diminished vigilance could be observed in all of the skippers when optokinetic nystagmus was tested. CONCLUSION: The pupillograph represents a suitable device for measuring functions of the visual and vegetative systems. Thus, the impact of these functions on nautical capability can be demonstrated. If further investigations such as ophthalmological, medical, psychological, and nautical evaluations are taken into account, it could be determined that blood alcohol levels of 1.0 per thousand may exclude safe navigation.

Accidents↗
PubMed2004

Bilateral optic neuropathy and unilateral tonic pupil associated with acute human herpesvirus 6 infection: a case report.

BACKGROUND: Human herpesvirus 6 (HHV-6), a widespread virus and causative agent of exanthema subitum in children, has been associated with a number of neurologic disorders including cranial nerve palsies, seizures, encephalitis, meningitis, and multiple sclerosis. PATIENT: A 31-year-old man presented with bilateral optic neuropathy, disc edema, and unilateral tonic pupil, which were found to be associated with acute HHV-6 infection. The patient had been suffering from juvenile diabetes for 5 years. One week after onset of intravenous antiviral therapy with foscarnet, disc edema subsided, and tonic pupil reaction was no longer detectable. CONCLUSIONS: HHV-6 infection may play a role as a causative agent in patients with optic neuropathy and tonic pupil.

Adult↗
PubMed1977

Pupil size after use of marijuana and alcohol.

In an experiment using ten subjects, marijuana produced a dose-related constriction of the pupil at low photopic light levels; alcohol produced no effect on pupil size. The two drugs in combination produced no change in pupil size.

Adult↗
PubMed1982

A comparison of the effects of pirenzepine and atropine on gastric acid secretion, salivary secretion and pupil diameter in the rat.

The ability of pirenzepine and atropine, given i.v., to inhibit gastric acid and salivary secretion and increase pupil diameter has been assessed in the rat. Pirenzepine had a similar potency against acid secretion, ED 50 0.71 (0.41 to 1.1) mg.kg-1, and salivary secretion, ED 50 (0.43 to .59) mg.kg-1, whilst its potency was less in the eye, ED 50 1.8 (1.6 to 2.1) mg.kg-1. Atropine however, was more potent in reducing salivary secretion, ED 50 0.012 (0.010 to 0.016) mg.kg-1 and increasing pupil diameter, ED 50 0.028 (0.025 to 0.031) mg.kg-1 than in inhibiting gastric acid secretion, ED 50 0.056 (0.037 to 0.083) mg.kg-1. Therefore, that quantity of pirenzepine which inhibits gastric acid secretion by 50% will have only a slight effect on the eye and will inhibit salivary secretion by a similar magnitude. In contrast, the amount of atropine required to inhibit acid secretion by 50% will significantly increase pupil diameter and abolish salivary secretion.

Animals↗
PubMed1985

Effect of pupil size on steady state accommodation.

Experiments are described in which monocular accommodation response/stimulus curves were measured with Snellen targets over the stimulus range from +1.0 to -5.0 D, using artificial pupils with diameters of 1.0, 1.5, 2.0, 2.5 and 3.0 mm and a constant retinal illuminance of 600 td. The results agree with those of earlier authors in showing a diminished response with smaller pupils. The slopes of the quasi-linear central portions of the response/stimulus curves are well described in terms of a geometrical optical approximation in which the accommodation system works to produce a retinal blur circle whose diameter is a linear function of the dioptric difference between the magnitudes of the stimulus and the accommodative resting state, this blur circle diameter being independent of the pupil diameter. Further consideration of diffractive effects suggests that contrast changes in the intermediate spatial frequency components (approximately 5 c/deg) of the retinal image may play a dominant role in guiding the response.

Accommodation, Ocular↗
PubMed1990

On the effective optical density of the pupil mechanism in fly photoreceptors.

A simple electrophysiological method is described for determining the effective optical density of the intracellular pupil mechanism of insect photoreceptor cells. The method depends on the fact that the photoreceptors can not only be illuminated in the normal, orthodromic way, but also antidromically, i.e. from the back. Two assumptions are made: (i) the receptor potential generating process is invariant for the direction of the incident light; (ii) the pupil mechanism is locally driven and only active distally in the cell. The method was tested in the blowfly Calliphora erythrocephala. The two assumptions appeared to be valid there. The electrophysiologically estimated effective optical density of the pupil was equal to the optically measured absorbance over the investigated two log-unit range.

Adaptation, Ocular↗
PubMed2003

A case of angle closure glaucoma caused by plateau iris and adie's pupil.

PURPOSE: To describe a case of plateau iris associated with bilateral Adie's pupil. DESIGN: Interventional case report. METHODS: A 54-year-old woman presented with pain in her right eye and headache. Intraocular pressure was 34 mm Hg in the right eye. Light reflex was defective bilaterally. RESULTS: Ultrasound biomicroscopic imaging revealed normal anterior chamber depth and narrow angle. The ciliary processes were situated anteriorly. The eyes showed supersensitivity to 0.125% pilocarpine. The patient was diagnosed as having bilateral angle-closure glaucoma induced by Adie's pupil and plateau iris. CONCLUSION: Mild pupillary dilation caused by Adie's pupil may have played a role in the development of angle closure in the plateau iris configuration of our patient.

Anterior Chamber↗
PubMed1998

Pupil-sparing third nerve palsy associated with sildenafil citrate (Viagra).

PURPOSE: To report unilateral pupil-sparing third nerve palsy after use of sildenafil citrate (Viagra). METHOD: Case report. RESULTS: A 56-year-old man with a history of tobacco abuse was treated for erectile dysfunction. Viagra, 50 mg, was taken once without adverse effect. Three weeks later, the patient took a second dose of Viagra (50 mg); 36 hours later he experienced a complete pupil-sparing third nerve palsy. Erythrocyte sedimentation rate, blood glucose level, magnetic resonance imaging, and magnetic resonance angiography were normal. CONCLUSION: In a patient with microvascular disease, use of sildenafil may be associated with pupil-sparing third nerve palsy.

Blood Glucose↗
PubMedDate not supplied

Estimation of anterior nucleus of lens by Scheimpflug image before and after pupil dilatation.

PURPOSE: To compare the accuracy of lens transparency evaluations by Scheimpflug image in the anterior nucleus of the lens before and after pupil dilatation. METHODS: Scheimpflug lens images were recorded in 70 eyes of 38 subjects (age: 28-75 years) before and after pupil dilatation, and light scattering intensity measurements before and after dilatation were compared. RESULTS: There was a significant positive correlation between the light scattering intensity before and after dilatation at the anterior cortex, anterior nucleus, and central clear zone of the lens (r > 0.9, P <.0001). CONCLUSIONS: It is possible to estimate the transparency in the anterior nucleus of the lens from the Scheimpflug image without pupil dilatation. If nuclear type cataracts are regarded as a structural marker of aging in epidemiological studies, measuring the light scattering intensity in the anterior nucleus of the lens without dilatation seems to be a safe, useful, and quantitative method.

Adult↗
PubMed2000

Spontaneous fluctuations in pupil size are not triggered by lens accommodation.

Fluctuations in pupil size and lens accommodation are measured concurrently under open loop conditions, constant illumination and far fixation. In 12/17 trials no correlation was measured between the fluctuations in pupil size and lens accommodation. For the remaining 5/17 trials no lag was observed between the changes in pupil size and lens accommodation indicating that this correlation does not arise as a consequence of a near response. These observations suggest that under conditions of constant illumination and far fixation, the supranuclear centers controlling the near response are not active.

Accommodation, Ocular↗
PubMed1983

Pupil capture: prevention and management.

Pupil capture occurs in a small percentage of patients following posterior chamber lens implantation. We noted a 3% incidence in 100 patients using sulcus fixated planar J-loop lenses, a 1% incidence using sulcus fixated angulated J-loop lenses, and a 1% incidence in capsular bag fixated flexible Y-loop lenses. No patients lost vision from pupil capture, and no clinically significant late complications were observed. Pupil capture may be successfully treated in the early postoperative period in some patients by mydriasis and a noninvasive loop compression technique using Q-tips.

Anterior Chamber↗
PubMed1982

The Marcus Gunn pupil in experimental tract lesions.

Isolated surgical lesions were made in three Macaca mulatta monkeys. Two had right optic tract section. One control underwent section of the right half of the chiasm. Preoperative evaluation revealed no fundus, pupil, or VER abnormalities. Postoperatively, a classic Marcus Gunn pupil was found contralateral to the isolated optic tract lesions. The control had normal pupils. The nature of the lesions was documented histopathologically, the pupillary findings, photographically. Possible explanations are explored. Contrary to traditional teaching, lesions occurring posterior to the chiasm may indeed produce the Marcus Gunn pupillary phenomenon.

Animals↗
PubMed1990

Rapid determination of intraocular lens tilt and decentration through the undilated pupil.

The apparent optical axis of an implanted intraocular lens (IOL) can be located by alignment of the examiner's hand light with the third and fourth Purkinje images from the front and back surfaces of the IOL. Tilt of the IOL can be estimated (or measured with an arc perimeter) by the angle between the apparent optical axis and the patient's line of sight (actual tilt approximately 0.85 x apparent tilt). Decentration of the IOL is easily detected, equal to the distance of the IOL optical axis from the center of the pupil. This simple technique can be used through the natural pupil with posterior chamber IOLs, providing the optical axis of the malpositioned IOL still passes through the pupil.

Humans↗