<prompt> Homers syndrome. All true except-MiosisAnhydrosisHyperchromatic irisApparent exophthalmos  <response>: Horners syndrome, also known as oculosympathetic paresis is a combination of symptoms that arises when a group of nerves known as the sympathetic trunk is damaged. The signs and symptoms occur on the same side ipsilateral as it is a lesion of the sympathetic trunk. It is characterized by miosis a constricted pupil, paial ptosis a weak, droopy eyelid, apparent anhydrosis decreased sweating, with apparent enophthalmos inseed eyeballs Signs that are found in people with Horners syndrome on the affected side of the face include the following: ptosis drooping of the upper eyelid anhidrosis decreased sweating miosis constriction of the pupil sinking of the eyeball into the face inability to completely close or open the eyelid facial flushing headaches loss of ciliospinal reflex bloodshot conjunctiva, depending on the site of lesion. unilateral straight hair in congenital Horners syndrome; the hair on the affected side may be straight in some cases. heterochromia iridum in congenital Horners syndrome Interruption of sympathetic pathways leads to several implications. It inactivates the dilator muscle and thereby produces miosis. It inactivates the superior tarsal muscle which produces ptosis. It reduces sweat secretion in the face. Patients may have apparent enophthalmos affected eye looks to be slightly sunken in but this is not the case. The ptosis from inactivation of the superior tarsal muscle causes the eye to appear sunken in, but when actually measured, enophthalmos is not present. The phenomenon of enophthalmos is seen in Horners syndrome in cats, rats, and dogs. Sometimes there is flushing on the affected side of the face due to dilation of blood vessels under the skin. The pupils light reflex is maintained as this is controlled the parasympathetic nervous system. In children, Horners syndrome sometimes leads to heterochromia, a difference in eye color between the two eyes.This happens because a lack of sympathetic stimulation in childhood interferes with melanin pigmentation of the melanocytes in the superficial stroma of the iris. In veterinary medicine, signs can include paial closure of the third eyelid, or nictitating membrane. Ref Harrison20th edition pg 2567 