The setting sun sign or sunset eye sign or setting sun phenomenon is a clinical phenomenon encountered in infants and young children with raised intracranial pressure.

It is an ophthalmologic sign  resulting from upward-gaze paresis. In this condition, the eyes appear driven downward, the sclera can be seen between the upper eyelid and the iris. Part of the lower pupil may be covered by the lower eyelid.

It is an earlier sign of hydrocephalus than enlarged head circumference. Despite the fact that setting sun eye is a grave sign, most commonly accompanied by other neurological signs and symptoms suggesting serious diseases full fontanels, separation of sutures, irritability vomiting. This sign is a valuable early warning of an entity requiring urgent neuroimaging and urgent neurosurgical intervention.Also it  is apart of Parinaud’s syndrome.

Epidemiology

Seen in up to 40% of children with obstructive hydrocephalus and 13% of children with shunt dysfunction

Pathogenesis

 Pathogenesis of this sign is not well understood, but it seems to be related periaqueductal dysfunction rather than the mechanical displacement as the possible mechanism for this sign secondary to increased intracranial pressure.