Changes in ocular biometry and anterior chamber parameters after pharmacologic mydriasis and peripheral iridotomy in primary angle closure suspects / Cambios en la biometría ocular y los parámetros de la cámara anterior tras midriasis farmacológica e iridotomía periférica en sospechas de cierre angular primario

Purpose: The aim of this study was to evaluate the effects of pharmacologic mydriasis and Peripheral Iridotomy (PI) on ocular biometry and anterior chamber parameters in primary angle closure suspects. Methods: In this prospective interventional case series, 21 primary angle closure suspects were enrolled. Intraocular pressure, refraction, ocular biometry (Lenstar, LS900), and anterior chamber parameters (Pentacam HR) were measured at four occasions: before PI (before and after mydriasis with phenylephrine) and two weeks after PI (before and after mydriasis). The study was conducted on both eyes and only one eye per patient, in random, was included in the analysis. Results: The mean age of the participants was 60±7 years and 17 (81%) were female. There were no significant differences in intraocular pressure, refraction, keratometry, biometric and anterior chamber parameters between groups, except for anterior chamber volume, which showed increments with PI and mydriasis. The corresponding values for anterior chamber volume were as follows: 88.2±13.7mm3 before PI, undilated; 106.3±18.8 before PI, dilated; 99.0±14.6 after PI, undilated, and 107.4±16.5 after PI, dilated (P<0.001). Conclusions: This study showed no change in the ocular biometric and anterior chamber parameters including iridocorneal angle after PI and/or pharmacologic mydriasis except for increments in anterior chamber volume. This factor has the potential to be used as a numerical proxy for iris position in evaluating and monitoring patients with primary angle closure suspects after PI (AU)

Objetivo: El objetivo de este estudio fue el de evaluar los efectos de la midriasis farmacológica y la iridotomía periférica (IP) en la biometría ocular y los parámetros de la cámara anterior en las sospechas de cierre angular primario. Métodos: En esta serie de casos intervencional prospectiva, se incluyó a 21 sospechas de cierre angular primario. Se realizaron las mediciones siguientes: presión intraocular, refracción, biometría ocular (Lenstar, LS900), y parámetros de la cámara anterior (Pentacam HR) en cuatro ocasiones, antes de la IP (antes y después de la midriasis con fenilefrina) y dos semanas después de la IP (antes y después de la midriasis). El estudio se realizó en ambos ojos, incluyéndose en el análisis un solo ojo por paciente de manera aleatoria. Resultados: La edad media de los participantes fue de 60±7 años, de los cuales 17 eran mujeres (81%). No se hallaron diferencias significativas en cuanto a presión intraocular, refracción, queratometría, parámetros biométricos y de la cámara anterior entre los grupos, exceptuando el volumen de la cámara anterior, que reflejó incrementos con la IP y la midriasis. Los valores correspondientes para el volumen de la cámara anterior fueron los siguientes: 88.2±13,7mm3antes de la IP, sin dilatación; 106.3±18,8 antes de la IP, con dilatación; 99.0±14,6 tras la IP, sin dilatación, y 107.4±16,5 tras la IP, con dilatación (P<0,001). Conclusiones: El presente estudio no reflejó cambios en los parámetros biométricos oculares y de la cámara anterior, incluyendo el ángulo iridocorneal tras la IP y/o midriasis farmacológica, exceptuando los incrementos del volumen de la cámara anterior. Este factor tiene el potencial de ser utilizado como indicador numérico de la posición del iris al evaluar y supervisar a los pacientes con sospechas de cierre angular primario tras IP (AU)

Midriasis benigna episódica. Experiencia en una consulta monográfica de neuro-oftalmología de un hospital terciario / Benign episodic mydriasis. Experience in a specialist neuro-ophthalmology clinic of a tertiary hospital

Introducción: Las anisocorias son un motivo de consulta relativamente frecuente en unidades de neuro-oftalmología (UNO). Suponen un reto diagnóstico por la variedad de procesos que pueden ocasionarla. En ausencia de síntomas acompañantes, suelen estar ocasionadas por procesos benignos. La midriasis benigna episódica (MBE) es una causa aislada de asimetría pupilar intermitente, de fisiopatología no esclarecida y predominio en mujeres jóvenes migrañosas. Sujetos, material y métodos: Describimos las características epidemiológicas y clínicas de los pacientes con MBE valorados en una UNO de un hospital terciario. Resultados: Un total de 7 pacientes fueron diagnosticadas de MBE. Todas eran mujeres, con edad media de 33 ± 10 años. Los motivos de consulta fueron asimetría pupilar (n = 5) y visión borrosa (n = 2) de presentación fundamentalmente unilateral (n = 6). La duración fue variable, desde minutos hasta 48 h. Cuatro pacientes (57%) presentaban como antecedente migraña sin aura. En estas, los episodios eran recidivantes (75%), de minutos de duración (75%) y asociaban visión borrosa (50%). Los estudios de neuroimagen (resonancia magnética cerebral) fueron normales. Discusión: La midriasis benigna episódica se presenta predominantemente en mujeres jóvenes. Se asocia al antecedente de migraña y hace plantear si se trata de un síntoma acompañante de la migraña, un aura migrañosa o de migraña oftalmopléjica. De predominio unilateral, puede sin embargo existir alternancia del ojo afectado o ser bilateral de forma simultánea, lo que nos hace cuestionarnos la idoneidad del término. En ausencia de síntomas acompañantes y en episodios de corta duración, no consideramos necesaria la realización de pruebas de imagen

Introduction: Anisocorias are a relatively frequent reason for consultation in neuro-ophthalmology units. They remain a diagnostic challenge for specialists as they may be due to several etiological factors. In the absence of other accompanying symptoms, anisocorias are usually due to benign processes. Benign episodic mydriasis (BEM) is an isolated cause of intermittent pupil asymmetry, in which the pathophysiology is still not fully understood, and is predominant in young women with migraine. Subjects, material and methods: We describe the epidemiological and clinical characteristics of patients with BEM, assessed in a neuro-ophthalmology unit in a tertiary hospital. Results: A total of 7 patients were diagnosed with BEM, all of them females, with a mean age of 33 ± 10 yrs. The patients presented with pupil asymmetry (n = 5) and blurred vision (n = 2), and 6 of the 7 patients had unilateral involvement. The duration of impairment varied from a few minutes to 48 hrs. Four patients (57%) had a clinical history of migraine without aura. The episodes in these 4 patients were recurrent (75%), often lasted for a few minutes (75%), and had associated blurred vision (50%). The neuroimaging studies were normal. Discussion: BEM appears predominantly in young women. It is frequently related to a previous history of migraine, and the specialist must consider if it is a concomitant symptom of common migraine, migraine with aura, or ophthalmoplegic migraine. Although BEM has unilateral predominance, there may be alternation of the affected eye or even bilateral impairment during the same episode, which makes us question the adequacy of the term to describe the process. Imaging tests are not recommended in the absence of other accompanying symptoms, or in short-term episodes

Formulation and characterization of atropine sulfate in albumin-chitosan microparticles for in vivo ocular drug delivery.

The overall study goal was to produce a microparticle formulation containing atropine sulfate for ocular administration with improved efficacy and lower side effects, compared with that of the standard marketed atropine solution. The objective was to prepare an atropine sulfate-loaded bovine serum albumin-chitosan microparticle that would have longer contact time on the eyes as well as better mydriatic and cycloplegic effect using a rabbit model. The microparticle formulation was prepared by method of spray-drying technique. The percent drug loading and encapsulation efficiency were assessed using a USP (I) dissolution apparatus. The particle sizes and zeta potential were determined using laser scattering technique and the surface morphology of the microparticles was determined using a scanning electron microscope. The product yield was calculated from relative amount of material used. In vitro cytotoxicity and uptake by human corneal epithelial cells were examined using AlamarBlue and confocal microscopy. The effects of the microparticle formulation on mydriasis in comparison with the marketed atropine sulfate solution were evaluated in rabbit eyes. The prepared microparticle formulation had ideal physicochemical characteristics for delivery into the eyes. The in vivo studies showed that the microparticles had superior effects on mydriasis in rabbits than the marketed solutions

Rat clonidine mydriasis model: imidazoline receptors are not involved.

The clonidine mydriasis model in rats has been widely applied in preclinical research to characterize alpha(2)-adrenoceptor antagonistic properties of drugs. The present study was undertaken to pharmacologically determine if imidazoline I(1) receptors are also involved in this model system. Sigmoid dose-response curves for pupillary dilation were produced in pentobarbital anesthetized rats by intravenous administration of increasing doses of agonists (guanabenz for alpha(2)-adrenoceptors, clonidine for both alpha(2)-adrenoceptors and imidazoline I(1) receptors, and rilmenidine for imidazoline I(1) receptors). Two antagonists (RS 79948 for alpha(2)-adrenoceptors and efaroxan for imidazoline I(1) receptors) were used to antagonize the mydriasis elicited by those three agonists, with antagonistic potencies calculated. In additional experiments, we examined the effect of the selective imidazoline I(1) receptor antagonist, AGN 192403, on clonidine-induced mydriasis. The results showed that pupillary response curves elicited by guanabenz, clonidine and rilmenidine were competitively antagonized by both RS 79948 (0.03-1 mg/kg) and efaroxan (0.03-1 mg/kg) in a dose-related fashion. The potencies of either antagonist against the three agonists were not significantly different. AGN 192403 (5 mg/kg) did not significantly shift the clonidine mydriasis curve. These results suggest that imidazoline I(1) receptors are not functionally involved in the rat clonidine mydriasis model and support this in vivo system as a useful model for studies of alpha(2)-adrenoceptors.

Studies of alpha-adrenoceptor antagonists on sympathetic mydriasis in rabbits.

This study was undertaken to identify the alpha-adrenergic receptor type responsible for sympathetically evoked mydriasis in pentobarbital-anesthetized rabbits. Frequency-response curves of pupillary dilation were generated by stimulation of the preganglionic cervical sympathetic nerve (1-64 Hz). Evoked mydriatic responses were inhibited by systemic administration of nonselective alpha-adrenergic antagonists, phentolamine (0.3-10 mg/kg) and phenoxybenzamine (0.03-0.3 mg/kg), as well as the selective alpha(1)-adrenergic antagonist, prazosin (0.1-1 mg/kg). The alpha(2)-adrenergic antagonist, RS 79948 (0.3 mg/kg, i.v.) was without inhibitory effect, but potentiated the mydriatic response. In addition, the selective alpha(1A)-adrenoceptor antagonist, 5-methylurapidil (0.1-1 mg/kg, i.v.), antagonized the elicited mydriasis in a dose-dependent fashion. Unlike previous observations that prazosin does not block the adrenoceptor in rabbit iris dilator muscle, our results suggest that prazosin is effective in inhibiting neuronally elicited mydriasis in this species, and that alpha(1A)-adrenoceptors appear to mediate the response.

Ocular pharmacokinetics and convectional flow: evidence from spatio-temporal analysis of mydriasis.

Pupil shape and placement were studied during pharmacologic dilation, using a photographic technique. Dilation onset was highly asymmetric; typically, the inferior or inferior-nasal side of the pupil moved maximally, while the opposite side barely moved. Pupil shape tended to elongate at a large angle to the direction of maximum shift. Late in dilation, pupils returned to more circular shape and pupil centers returned to near their original position. Results when a subject's head was inverted during and immediately after drug administration were essentially unchanged. However, results when a subject's head was rolled on one side (and kept there) after administration were markedly different; the dilation pattern shifted roughly in accord with head tilt. It is proposed that anterior chamber convectional flow is responsible for the asymmetry. Supportive evidence was obtained from experiments in which cooled or heated gel-packs were applied to the lids. Analysis indicates that convectional flow makes a very substantial contribution to anterior segment pharmacokinetics and is also likely to be of general importance in anterior segment transport.