Horner's syndrome, also known as oculosympathetic paresis,[1] is a combination of symptoms that arises when a group of nerves known as the sympathetic trunk is damaged.

Once the syndrome has been recognized, medical imaging and response to particular eye drops may be required to identify the location of the problem and the underlying cause.

[3] Signs that are found in people with Horner's syndrome on the affected side of the face include the following: Interruption of sympathetic pathways leads to several implications.

The ptosis from inactivation of the superior tarsal muscle causes the eye to appear sunken in, but when actually measured, enophthalmos is not present.

[citation needed] Horner's syndrome is usually acquired as a result of disease, but may also be congenital (inborn, associated with heterochromatic iris) or iatrogenic (caused by medical treatment).

In rare cases, Horner's syndrome may be the result of repeated, minor head trauma, such as being hit with a soccer ball.

In addition to the blown pupil in a CNIII (oculomotor nerve) lesion, this ptosis is much more severe, occasionally occluding the whole eye.