What are Setting Sun Eyes (Sunset Eyes)?
Setting sun eyes is when the eyes appear stuck in a downward gaze with the pupil covered by the lower eyelid. It’s also called ‘the sunset eye sign’ or ‘setting sun phenomenon.’
The setting sun sign is most common in infants and young children. It can be a valuable early warning sign of increased intracranial pressure.
Forty percent of children diagnosed with obstructive hydrocephalus (problems with circulation and reabsorption of cerebrospinal fluid ) also have sunset eyes.1
What Causes Sunset Eyes?
The most common causes of persistent sunset eyes are hydrocephalus and shunt dysfunction, which can cause Parinaud syndrome (a neurological disorder).
Periodic or transient setting sun phenomenon can also occur in healthy infants when they are repositioned or removed from light. This reaction is typical because infants have an immature eye reflex system.
Hydrocephalus is cerebrospinal fluid (CSF) buildup in the brain, resulting in elevated intracranial pressure. The name translates to "water on the brain."
Typical causes of hydrocephalus include overproduction of CSF, infection, or a blockage in the flow of CSF.
Hydrocephalus can lead to sunset eyes when elevated intracranial pressure affects the part of the brain that controls eye movement.
Hydrocephalus is commonly treated by connecting a shunt (flexible tube with a catheter and valve) to aid the flow of CSF from a brain ventricle to the abdomen.
A shunt malfunction can lead to a backup of CSF, resulting in high intracranial pressure.
If someone with a shunt placement is also experiencing sunset eyes, it typically means your doctor must fix a shunt dysfunction.
Thirteen percent of children with the setting sun sign have also had a shunt malfunction.3
Parinaud syndrome (PS), or dorsal midbrain syndrome, is a neurological disorder resulting in up-gaze palsy, an inability to move the eyes upwards. It can make the eyes turn downward in a fixed downward gaze.
Sunset eyes are present in 87 to 100% of people with PS.4
Lesions in the part of the brain that controls the vertical movement of the eyes cause Parinaud syndrome. Common causes of lesions include:
Who Can Develop This Condition?
The setting sun eye phenomenon is most common in infants and young children who develop a neurologic condition that disrupts the part of the brain that controls eye movement.
Healthy infants can also spontaneously develop a benign setting sun phenomenon without any signs of illness or disease. It may occur due to changing the infant's position or removing light.
Sunset eyes not associated with a neurological condition typically go away without treatment or intervention, usually before age two.
Signs and Symptoms of Sunset Eyes
Common signs and symptoms of sunset eyes include:
- Eyes fixed in a downward gaze
- Eyes appear driven down and unable to look upward
- The pupil is covered by the lower eyelid giving it the "sunset" appearance
- The sclera (white of the eye) is between the upper eyelid and the iris (colored part).
Hydrocephalus is a neurological condition that typically leads to the setting sun sign. Sunset eyes are a critical early warning sign of hydrocephalus.
Other warning signs of hydrocephalus include:
- Enlarged head circumference
- Bulging fontanelle (soft spot on a baby’s head)
- Uncontrolled vomiting
- Shaky eyes (nystagmus)
- Crossed eyes (strabismus)
How are Sunset Eyes Treated?
Sunset eyes are treated by first finding and eliminating the underlying cause of increased intracranial pressure.
The sunset eye phenomenon is most commonly associated with hydrocephalus, which doctors treat surgically. If not treated quickly, it can lead to brain damage.
There are two ways to treat hydrocephalus surgically, which include:
- Endoscopic third ventriculostomy (ETV): A small hole is made in the brain's third ventricle to relieve fluid and pressure.
- Shunt surgery: A drainage tube is inserted from a brain ventricle to the abdomen to remove fluid from the brain.
Treatment for Parinaud syndrome also depends on the underlying cause. It may include tumor removal or treatment for hydrocephalus (a common cause of PS).
Sunset eyes are associated with infants and young children with increased intracranial pressure, typically caused by hydrocephalus (fluid on the brain). Sunset eyes can be a fixed downward gaze with the pupil covered by the lower eyelid giving it a "sunset" appearance.
Treatment involves finding and eliminating the underlying cause of elevated pressure. It typically involves inserting a shunt (drainage tube) from a brain ventricle to the abdomen to relieve fluid and strain off the brain.
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