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Exophthalmos, Enophthalmos, and Strabismus in Dogs

Exophthalmos, enophthalmos, and strabismus are all diseases which cause the dog's eyeball to be abnormally positioned.

With exophthalmos, the dog's eyeball protrudes, or bulges, from the orbit of the eye. This may be due to a space-occupying mass behind the eyeball. Enophthalmos, meanwhile, causes the eyeball to recess, or sink, into the skull. Lastly, strabismus is when an affected animal's eye appears to look off at a different angle, unable to focus in the same direction as the other eye. This can occur with one or both eyes, and is more commonly referred to as "crossed eyes."

The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.

Symptoms and Types

The signs for each of these disease are as follows:

1. Exophthalmos:
   • Fever
   • General malaise
   • Swollen eyelid
   • "Cherry eye"
   • Loss of vision
   • Pockets of pus in or around the eye (orbital abscess)
   • Discharge from the eyes that is watery (serous) or mucous mixed with pus (mucopurulent)
   • Lagophthalmos (inability to close the eyelids completely)
   • Inflammation of the cornea (transparent coating of the eye) or surrounding tissue
   • Pain on opening the mouth
2. Enophthalmos:
   • Entropion
   • "Cherry eye"
   • Wasting of the muscle surrounding the eye (extraocular muscle atrophy)
3. Strabismus:
   • Deviation of one or both eyes from the normal position
   • Decreased functioning of the muscles surrounding the eye

Causes

Exophthalmos is generally due to a space-occupying mass located behind the eyeball. Strabismus, or "crossed eyes," is usually caused by an imbalance of extraocular (outside of the eye) muscle tone. The Shar-pei is highly susceptible to this eye disease.

Some other factors that may lead to these eye diseases include:

1. Exophthalmos:
   • Bleeding within the eye
   • Pockets of pus within the eye
   • Inflamed eye tissue (bacterial or fungal in nature)
   • Inflamed or swollen sac of mucous in the bone that surrounds the eye socket
   • Inflammation in the muscles surrounding the eye(s)
   • Arteriovenous fistula (when arteries join with veins, and a new, abnormal passage is formed); this is rare
2. Enophthalmos:
   • Cancer
   • Dehydration (it affects the water content within the eyeball)
   • Drooping eyelid
   • Constricted pupils
   • Collapsed globe
   • Loss of volume in the eyeball (i.e., the eyeball is shrunked and usually non-functional)
   • Horner’s Syndrome (a lack of nerve distribution to the eye and/or a loss in the supply of nerves)
3. Strabismus:
   • Genetics
   • Restriction of eye muscle mobility from scar tissue (usually from previous trauma or inflammation)
   • Abnormal crossing of visual fibers in the central nervous system

Diagnosis

You will need to give a thorough history of your dog's health, onset of symptoms, and possible incidents that might have preceded this condition. Your veterinarian will perform a thorough physical exam, examining the eyeballs, surrounding bone and muscle, and an inspection of your dog's mouth for any abnormalities. X-ray imaging of the skull will help to determine the exact location of any growths, pockets of fluid, or abnormalities in the muscle or bone that might be contributing to the abnormal positioning of the eyeball.

Your veterinarian will also probably want to perform basic blood tests, including a chemical blood profile, a complete blood count, a urinalysis, and an electrolyte panel, just to make sure there is no underlying systemic disease involved.

Treatment

• Eyeball out of socket
  • Surgery: possible complications are excessively dry eyes (keratoconjunctivitis sicca)
• Abscess or inflammation of the eyeball
  • Surgery to drain the abscess
  • Collect samples for bacterial culture and microscopic examination
  • Hot packing
• Cancer of the eye
  • Usually begins in the eye and spreads
  • Operate early, removing the malignant mass, or the entire eyeball
  • If appropriate, chemotherapy or radiotherapy will be prescribed
  • Without chemotherapy or radiotherapy, survival is weeks to months if it is metastasizing malignant cancer (spreading cancer); end of life care or euthanasia may be only recourses
  • Veterinarian specializing in cancer may need to be consulted for specific care
• Zygomatic mucocele (a pocket of mucous in the bone surrounding the eyeball)
• Antibiotics and corticosteroids; surgery if necessary
• Strabismus
  • Nerve disorder: the underlying cause will be treated
  • Surgery to correct muscle abnormality, or therapy to strengthen muscles

Living and Management

Your veterinarian will schedule follow-up appointments dependent on your dog’s underlying diagnosis. For example, if your pet has an eye infection, your veterinarian will want to examine your dog at least weekly until signs of the disease have resolved.

If you see signs of any of these eye diseases returning, you will need to contact your veterinarian immediately to avoid permanent damage to the eye.