Studies on the experimental induction of ptosis in horses

The precise appearance of ptosis due to lesions at different sites was inve stigated in experimental ponies. The angles of the eyelashes to the head wa s used as an objective measurement of ptosis after local anaesthesia of the sympathetic trunk or the palpebral nerve and the administration of an ocul ar alpha agonist or antagonist. It tvas shown that ptosis is not an inevita ble consequence of palpebral nerve pathology, that ocular alpha antagonists can induce ptosis, and that a agonist eyedrops have an inconsistent effect on the equine pupil, but are consistent at reversing ptosis induced by sym pathetic denervation in unsedated horses. (C) 2000 Harcourt Publishers Ltd.