Which of the following signs is NOT associated with Horner's syndrome?

Horner's syndrome is a neurological condition that results from disruption of the sympathetic pathways to the eye, leading to a characteristic set of clinical signs. The hallmark signs associated with Horner's syndrome include miosis (constricted pupil), ptosis (drooping of the upper eyelid), and enophthalmos (sunken eye). These signs are due to the loss of sympathetic tone and the subsequent dominance of parasympathetic activity.

Proptosis, which refers to the protrusion of the eye, is not a feature of Horner's syndrome. Proptosis is typically a sign associated with conditions that cause an increase in retro-orbital pressure, such as trauma, orbital masses, or thyroid disease. In contrast, Horner's syndrome involves a decrease in sympathetic innervation and does not lead to protrusion of the eyeball.

Understanding the signs associated with Horner's syndrome is crucial for accurately diagnosing and managing conditions affecting the eye and surrounding structures. Medical professionals must differentiate these signs from those related to other ocular conditions to provide appropriate treatment.