Effect of topical betaxolol on the acute rise of aqueous flare induced by highly selective agonists for prostaglandin E2 receptor subtypes in pigmented rabbits

Laser flare-cell photometer: principle and significance in clinical and basic ophthalmology

A slit-lamp examination is an indispensable and essential clinical evaluation method in ophthalmology, but, it is qualitative subjective. To complement its weaknesses in making a quantitative evaluation of flare intensity and number of cells in the aqueous humor in the eye, we invented the laser flare-cell photometer in 1988. The instrument enables a non-invasive quantitative evaluation of flare intensity and number of cells in the aqueous with good accuracy and repeatability as well as maneuverability equal to slit-lamp microscopy. The instrument can elucidate the pathophysiology in the blood-aqueous barrier (BAB) function in a variety of ocular disorders. The accuracy of the instrument makes it possible to investigate not only the pathophysiology of intraocular disorders but also the effects of various drugs and surgical procedures in BAB. The instrument does not only lighten the burden on patients in clinical examinations and study but it also helps minimize the sacrifice of experimental animals and improves the reliability of the results by minimizing inter-individual variations through its good repeatability. Here I shall relate how the instrument has been applied to clinical and basic studies in ophthalmology and what novel knowledge its application contributed to pathophysiology in ophthalmology.

In vitro effects of preserved or preservative-free antiglaucoma medications on human complement system

PURPOSE

Antiglaucoma drugs have been associated with conjunctival and trabecular inflammatory cell infiltrates. However, the underlying mechanisms are still poorly understood. The aim of this study was to assess the effects of antiglaucoma medications on the complement system, an early mediator of the inflammatory response.

METHODS

Human serum was first treated with a classical or alternative pathway activator (aggregated human IgG or zymosan, respectively) in the presence or the absence of preservative-free or benzalkonium (BAK)-preserved antiglaucoma drugs. CH50 assay was then performed to assess the functional activity of residual complement in treated serum.

RESULTS

In the absence of complement activator, the antiglaucoma drugs tested in this study were all devoid of intrinsic complement-activating potency. Preserved and preservative-free carteolol as well as preserved latanoprost did not worsen or prevent complement activation induced by zymosan or aggregated IgG. Unexpectedly, both preserved and unpreserved timolol and betaxolol significantly counteracted the effects of complement activators. Timolol prevented activation triggered by both IgG and zymosan to the same extent (24% to 29%), despite the presence of BAK in the preserved formulation. Betaxolol was twice as effective at preventing the effect of IgG (34% to 37%) than that of zymosan (14%), regardless of the presence of BAK. However, BAK itself strongly aggravated complement activation by both activators.

CONCLUSIONS

Carteolol, timolol, betaxolol and latanoprost did not activate complement system. On the contrary, the beta-blockers timolol and betaxolol exerted an anti-inflammatory effect by preventing complement activation. The deleterious effect of benzalkonium seems to have been neutralized within the preserved eyedrops through a mechanism that remains to be elucidated. Our study suggests that inflammatory signs in glaucoma patients should not be attributed to complement activation by antiglaucoma drugs.