Iris Bombe in Cats: Causes, Symptoms, and Treatment
Iris bombe is a serious ocular emergency in cats that can threaten vision and comfort. Understanding what it is, how it develops, and what you can do if your cat shows signs of this condition is crucial for any cat owner or veterinary professional.
What Is Iris Bombe?
Iris bombe occurs when the iris—the colored part of your cat’s eye—forms a complete adhesion (called posterior synechiae) to the capsule of the lens. This means the iris sticks all the way around (a full 360 degrees) to the lens behind it. As a result, the iris bulges or billows forward into the front chamber of the eye (the anterior chamber). This abnormal shape isn’t just cosmetic—it blocks normal fluid movement inside the eye.
The obstruction stops aqueous humor (the clear fluid that nourishes the eye) from draining properly. This leads to increased intraocular pressure, which can cause pain and eventually blindness if not addressed quickly.
How Do Synechiae Cause Iris Bombe?
Synechiae are abnormal adhesions between parts of the eye. There are two main types:
- Anterior synechiae: The iris sticks to the cornea.
- Posterior synechiae: The iris sticks to the lens capsule.
Iris bombe specifically results from complete posterior synechiae. When this happens all around the pupil, fluid can't pass from behind the iris to in front of it. Pressure builds up behind the iris, pushing it forward like a sail catching wind.
Causes of Iris Bombe in Cats
The most common root cause is ocular inflammation (uveitis). Other triggers include:
- Trauma (fights, accidents)
- Chronic or severe infections
- Foreign body injuries
- Surgical complications
- Corneal ulcers
- Hyphema (bleeding at the front of the eye)
- Tumors (neoplastic processes)
- Congenital abnormalities
Certain infectious diseases are also linked with uveitis and subsequent iris bombe in cats: FIV, FeLV, FIP, toxoplasmosis, among others.
Signs and Symptoms
Cats with iris bombe may show several warning signs. Watch for:
- A bulging or distorted shape of one or both eyes
- Painful squinting or keeping an eye closed
- Redness and visible inflammation
- Lens cloudiness or opacity
- Tearing or unusual discharge from the eyes
- Cataracts, corneal lesions, ulcers, or scars
- Pupil abnormalities—irregular shape or poor reaction to light
- Changes in iris color or contour
- Lethargy or less interaction due to discomfort or vision loss
Diagnosis: How Vets Identify Iris Bombe
A veterinarian will perform a thorough ophthalmic exam using tools such as:
- Slit-lamp biomicroscopy: For detailed inspection of eye structures.
- Tonometry: To measure intraocular pressure.
- Fluorescein staining: To check for corneal ulcers.
- Gonioscopy: To evaluate drainage angles inside the eye.
- Ophthalmoscopy: For examining deeper structures like retina and optic nerve.
This comprehensive approach helps distinguish iris bombe from other causes of red or painful eyes and guides treatment decisions.
Treatment Options for Iris Bombe in Cats
Treatment aims both to address underlying causes (like infection or inflammation) and manage complications such as high intraocular pressure. Common strategies include:
- Corticosteroids/NSAIDs: Topical or systemic anti-inflammatories control uveitis.
- Mydriatic agents: These dilate pupils and may help break recent adhesions if caught early.
- Aqueous suppressants: Medications like carbonic anhydrase inhibitors or beta-blockers lower intraocular pressure if glaucoma develops.
- Surgical procedures: Synechiolysis (breaking adhesions) or laser iridotomy may be needed for severe cases.
- Treating infection: Antibiotics/antifungals if infection is present.
- Treating systemic disease: Addressing underlying conditions such as FeLV/FIV if identified.
Your vet will recommend regular rechecks to monitor progress and adjust therapy as needed. Early intervention offers better chances for vision preservation but prognosis remains guarded with chronic inflammation or secondary glaucoma.
Can You Prevent Iris Bombe?
You can't always prevent this condition but you can reduce risk by:
- Treating any eye trauma promptly—don’t wait if your cat’s been scratched near an eye!
- Keeps vaccinations up-to-date against infectious causes of uveitis where possible.
- Avoid situations where fights are likely—especially for outdoor cats prone to injury.
- Create a clean environment to minimize infection risk.
Iris Bombe Isn’t Contagious—but It’s Serious!
This condition doesn’t spread between animals but often follows injury or active uveitis. If you notice any change in your cat’s eyes—especially pain, squinting, redness, cloudiness—or behavioral changes like hiding more than usual, seek veterinary help immediately. Quick action can make all the difference for your cat’s comfort and sight!
