The College of Optometrists

Horners Syndrome

This gives a person with (often) sudden onset anisocoria (unequal pupil size). There may be an associated upper lid partial drop on the same side (this is due to loss of sympathetic innervation to Mullers muscle in upper lid).

The anisocoria is worse in the dark - when the 'good' eye will dilate, but the affected pupil will not dilate (because the pupil is sympathetic controls the DILATOR muscle).

(unequal pupil size)(note: upto 2mm difference is normal (idiopathic anisocoria) and can be checked because the pupil refex remain comitant)(move together). Note again: idiopathic anisocoria can vary on a day to day basis).

Confirmation test for Horners is 4% Cocaine eye drops into the affected (smaller pupil) eye.(at eye clinic, optoms are not permitted to use this drug). Cocaine blocks the reuptake of the sypathetic/ muscle transmitter noradrenalin. So cocaine causes a buildup of noradrenalin at the muscle receptor plate - causing a 'normal' pupil to dilate. However, if there is no noradrenalin 'cos the sympathetic nerve is damaged = then there will be little/no dialtion. So a posative result with Horners : Cocaine test = still anoscoria. Normal : Cocaine test = anisocoria gets better.

A further test would be with 1% hydroxyamphetamine drops. This is used to show if the lesion is pre or post ganglionic. Hydroxyamphetamine drops act to release noradrenalin from the storage areas of the nerve end plate.

So If pre ganglionic : the hydroxyamphetamine WILL dilate the pupil Post ganglionic : the hydroxyamphetamine WILL NOT dilate the pupil

That is because if the lesion is post ganglionic then the stores of noradrenalin will become depleted, so when the hydroxyamphetamine chemically signals release the noradrenalin = there is non to release - so the pupil stay small.

there are many causes of Horners, from whip lash neck injuries (hurting the nerve) to vascular problems due to diabetes or hypertension. Horners is an emergency referal because you can't do the needed tests. It is rare in general practice - but one day you will see it. hope it helps - steve