Ageing and alpha1 adrenoceptors in the iris

Abstract

SummaryThis study was undertaken to determine if the age related decrease in pupil size is attributable to altered sympathetic adrenoceptor responsiveness. Log dose response curves using the selective alpha! agonist phenylephrine and antagonist thymoxamine showed that there is no difference in alpha! adrenoceptor sensitivity in the elderly and the young. Therefore age related miosis is not caused by an alteration in alpha! receptors with age. SubjectsSixty healthy subjects were included in the study.Only those with blue-grey irides were included as the mydriatic response to sympathomimetic amines is inversely proportional to the degree of pigmenta tion of the iris,6 and the elimination of green, hazel or brown eyes served to reduce variability in response. Subjects were sub-divided into two groups. Group A were aged between 20 and 35 years (mean age of 23 years) and group B were aged between 65 and 90 years (mean age of 72 years).Each subject had a complete medical history taken and had a full physical examination. Ophthalmo logical assessment included pupillary reflexes, cor rected visual acuity, slit-lamp and fundal examination. Excluded from the study were mon ocular subjects and those with a corrected visual acuity of less than 6/12, subjects with ocular path ology or history of previous ophthalmic surgery.Also excluded were those with systemic disease and those on medication likely to affect the autonomic nervous system.Smoking and caffeine-containing beverages were not permitted on the day of the study. Alcohol was prohibited during the twelve-hour period preced ing and throughout the study.

Pharmacologic pupil dilation as a predictive test for the risk for intraoperative floppy-iris syndrome

“…For instance, the pupil decreases in size with advanced age, independent of a mydriatic effect. 11,26 In general, medical conditions associated with endothelial dysregulation (eg, congestive heart failure, diabetes, hypertension) have the potential to affect iris integrity. 11 However, the pharmacologic induction of mydriasis in this study was adequate to show the effect of a 1 -ARAs, in particular tamsulosin, on iris smooth musculature, with a reduction in the mydriatic Figure 1.…”

Intracameral Mydriatics in Cataract Surgery

“…It is well known that pupil sizes get generally smaller with age. It has been demonstrated, however, that there is no difference in   -adrenoceptor sensitivity in the elderly and the young, and thus, age related miosis is not attributable to an alteration in the iris   -receptors with age (Buckley, Curtin et al 1987). …”

A Pupillographic Evaluation of a Phenylephrine HC1 5% - Tropicamide 0.8% Combination Mydriatic

“…While phenylephrine HC1 2.5% (or 10%) might be considered an ideal mydriatic because of its selective action on the pupil dilator muscle, its clinical use is limited since phenylephrine HCl-induced mydriasis shows little or no resistance to the pupil constrictor action of bright light (1-3). However, it may show higher efficacy in older patients in whom the resting pupil is usually smaller than in young adults (4,5) .…”