Review: mediation of the ocular response to injury.

The structure of the anterior segment of the eye provide aqueous humour for metabolic traffic, regulation of intraocular pressure and the maintenance of a functional permeability barrier to separate internal compartments from general systemic influences. Irritative and injurous insults to the eye elicit an acute defensive miotic and vascular response which upsets the aqueous dynamics and provokes the influx of blood plasma proteins into the aqueous chambers. These events are initiated by antidromic activation of sensory elements within the anterior segment, releasing substance P and calcitonin gene-related peptide (CGRP) which, in lower mammals at least, stimulate respectively the miotic and vascular reactions. Considerable species differences can be found in the responsiveness of the eye to injury and in the effects of exogenous CGRP and substance P.