A closer look: Sunken Eyes in Cats
The severity of sunken eyes depends on several factors including:
- Whether the symptom affects one eye or both
- Whether the onset is gradual, sudden, or is present from birth
- Whether the cause affects other organs or not
- Whether the eyesight is affected
In cases where one eye is affected, it is more likely that the cause is traumatic injury, such as a fracture of the orbital bone, or the growth of a mass. When both eyes are affected, the cause is more likely to be systemic, such as severe dehydration or weight loss.
In cases where the onset is sudden, it is more likely that a traumatic injury is the cause. More gradual onset of sunken eyes is often associated with tumors or weight loss. In some cases, the causes of sunken eyes lead to sight loss or permanent blindness if not treated promptly.
Sunken eyes are the result of changes to the eyeball itself, or to the structures that hold the eyeball in place.
In some cases, the eyeball shrinks, allowing it to sink back into the eye socket. When the eyeball shrinks it is known as phthisis bulbi. Causes include:
- Inflammation of the eyeball
- Infection of the eyeball
- Leakage of aqueous fluid (the liquid inside the eyeball)
- Traumatic injuries to the eye
In some cases, the bone that holds the eyeball in place is fractured due to traumatic injury, creating more space behind the eyeball into which the eye retreats.
In some cases, the soft tissue surrounding the eyeball changes, causing the eye to sink. Causes include:
- Severe and rapid weight loss resulting in loss of fat or muscle behind the eye
- Mass growth in the sinus or eye socket pushing the eyeball back into the skull
In some cases, the nerves of the eye are disrupted due to Horner’s Syndrome.
In rare cases, cats are born with one eye that is smaller than the other, or both eyes that are smaller than usual.
Sunken eyes are uncommon in cats. Cats whose eyes are sunk back into the socket require immediate veterinary care, because some of the causes of this symptom result in blindness if left untreated.
Testing and diagnosis
Diagnostic tools to identify the underlying cause of sunken eyes include:
- Physical examination
- Ophthalmic examination
- Schirmer’s test (to determine tear production)
- Fluorescein staining (to check from damage to the surface of the eyeball)
- Tonometry (to check the pressure inside the eyeball)
- Reflex testing of the nerves of the head
- Blood tests
- Diagnostic imaging such as X-rays, CT scans, and MRIs
Treatment depends on diagnosis of the underlying cause, and may include:
- Pain relief
- Wound care
- Supportive care, such as IV fluids
- Dietary changes
In some cases, sunken eyes resolve on their own.
It is possible to mistake sunken eyes for other changes to the eyeball and surrounding structure, such as eyelid ptosis, where the eyelid droops over the eyeball.