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Glaucoma

Glaucoma doesn’t just affect humans---it affects all animals, including chickens. It is actually a group of eye conditions which occur when fluid builds up in the front part of the eye. This fluid exerts increased pressure within the eye, causing it to become enlarged and painful, leading to optic nerve damage.

Chickens can develop glaucoma as a primary condition or secondary to trauma. Glaucoma needs to be differentiated from other causes of exophthalmos (a bulging or enlarged eye).

For a definite diagnosis of glaucoma, your veterinarian will need to measure the intraocular pressure (IOP) within your chicken's eye. This is accomplished through the use of a handhold tonometer. A normal bird's eye will have an intraocular pressure of between 9.2 and 22 mmHg.

If caught early, there are some medical therapy options. These include:
  • Osmotic agents: This are known for producing rapid results, and as such are most frequently used during emergency management of glaucoma. The most commonly drugs used in animals include mannitol, glycerin and isosorbide. They are administered systemically and distributed to extracellular fluids, increasing plasma osmolality.
  • Carbonic anhydrase inhibitors (CAIs): These are known for their ability to inhibit the formation of bicarbonate in the ciliary body that is necessary for aqueous humor production. The most commonly used topical agents include dorzolamide and brinzolamide. CAIs are shown to be very effective in dogs and cats.
  • Beta-blockers: These are known for being highly effective in humans, and as such as the most commonly prescribed for treatment in people. They have been increasingly used for glaucoma treatment in animals, especially horses. Timolol is the most commonly used drug. Other topical beta-blockers include levobunolol, betaxolol, metipranolol and carteolol.
When the condition has advanced, surgery to remove the eye may be needed.

Clinical Signs

Enlargement of the eye
Blindness

Diagnosis

  • Clinical signs
  • Eye exam
  • Tonopen or Tonovet - Measurement of intraocular pressure

Treatment

NameSummary
Topical dorzolamideA type of carbonic anhydrase inhibitor that is applied two to three times a day initially, then titrated to effect (which may take up to 4 or 5 days).
Osmotic agentsMannitol, glycerin or isosorbide.
SurgeryEnucleation (eye removal) surgery, while under general anesthesia.

Prevention

Scientific References

Risk Factors

  • Prior history of trauma to the eye

Case Stories