Which condition may lead to a fixed and dilated pupil?

A fixed and dilated pupil can result from several conditions, but the most notable one is Adie's Pupil, also known as Adie's Tonic Pupil. This condition is characterized by a pupil that is larger than normal and reacts poorly to light. It occurs due to damage to the postganglionic fibers of the ciliary ganglion, which affects the muscles responsible for constricting the pupil when exposed to light or when focusing on near objects.

The fixed dilation is especially significant because, unlike other pupil responses that may change with light or accommodation, Adie's Pupil does not constrict properly. This results in a pupil that appears dilated and is unresponsive, which is an important diagnostic feature.

In contrast, the other conditions listed do not typically present with a fixed and dilated pupil. Amblyopia refers to a vision development problem in children, while Horner's syndrome leads to miosis (constricted pupils), and optic neuritis is an inflammation that affects the optic nerve and typically does not cause a fixed and dilated pupil. Understanding the specific characteristics of each condition helps in distinguishing the causes of abnormal pupil reactions in clinical practice.