Synechiae in Cats: Symptoms and Diagnosis

Have you noticed any changes in the way your cat’s eyes look? They may have developed a synechia. Synechiae in cats are abnormal attachments that can form between different structures inside the eye. 

What Is Synechiae in Cats?

A synechia (pronounced "sih-NEE-kee-uh") is an abnormal attachment between the iris (the colored part of the eye) and either the cornea (the clear front surface of the eye) or the lens behind the iris. When the iris sticks to the cornea, it's called anterior synechia.

When it sticks to the lens, it's called posterior synechia. 

Chronic uveitis (inflammation inside the eye) can cause either type. 

Synechiae themselves are not always a medical emergency, but they often occur alongside painful eye conditions that require prompt veterinary care. 

If your cat is squinting, keeping an eye closed, or showing signs of eye pain, have them examined by a veterinarian right away. 

Conditions such as glaucoma, lens luxation, corneal ulcers, and uveitis can cause similar signs and require urgent treatment. 

Symptoms of Synechiae in Cats

Symptoms of synechiae in cats include: 

• Irregularly shaped pupil 
• Spindle-like strands coming off the colored part of the eye 
• Cloudiness in the eye 
• Squinting 
• Pawing at the face 
• Excessive tearing 
• Sensitivity to light; vision changes 

Causes of Synechiae in Cats

Synechiae in cats is usually associated with inflammation inside the eye, particularly uveitis, as well as trauma or other ocular disease. 

The most common cause of synechiae in cats is uveitis. Uveitis is inflammation of the uvea, the middle layer of the cat’s eye that includes the colored iris. Uveitis can make the eye look cloudy. 

There are many different conditions that can lead to uveitis in cats. 

Underlying infections, chronic disease, and even cancer can all lead to uveitis. In some cats, the underlying cause is never identified. 

Infections can also lead to uveitis and secondary synechiae formation. 

Feline infectious peritonitis (FIP), feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), toxoplasmosis, and systemic fungal infections are recognized causes of feline uveitis.  

Bartonella infection has also been associated with uveitis in some cats, although its role can be difficult to establish. 

Trauma, such as an injury to the eye during a cat fight, can lead to inflammation and synechiae formation. 

Rarely, cats with a history of significant intraocular trauma or chronic eye damage can later develop post-traumatic ocular sarcoma, an aggressive cancer inside the eye. 

In severely damaged or nonfunctional eyes, a veterinarian may recommend enucleation (removal of the eye), depending on the extent of the injury and long-term risks. 

Deep corneal injury or perforation can also lead to synechiae formation. 

If the cornea is damaged deeply enough for the iris to contact the injured area, the iris may become attached to the cornea as the wound heals.    

Cancer can also lead to synechiae formation. Ocular lymphoma, iris melanoma, and post-traumatic ocular sarcoma can cause inflammation or bleeding inside the eye, which may contribute to adhesions between the iris and other structures. 

No particular cat breeds are known to be predisposed to synechiae. Cats who spend time outdoors may have greater exposure to trauma and some infectious diseases that can cause uveitis, which may indirectly increase their risk. 

How Veterinarians Diagnose Synechiae in Cats

Synechiae in cats are diagnosed with a thorough ophthalmic (eye) exam. Your cat’s veterinarian will use a tool called an ophthalmoscope to look inside your cat’s eye. 

Tonometry may also be used to check the pressure inside the eye. To do this test, a topical numbing drop may be put in your cat’s eye first, then a tool is used to gently touch the surface of the eye to obtain readings. They may also check your cat’s tear production and ocular reflexes. 

A fluorescein stain may also be used to check for corneal ulceration, particularly if the eye is painful or inflamed. 

If synechiae due to underlying uveitis are suspected, your vet may recommend blood work and testing for infectious or systemic diseases that can cause uveitis. 

Baseline lab work, FeLV/FIV testing, and toxoplasmosis testing may be recommended depending on your cat’s history or examination findings. 

Be sure to let your vet know if your cat has a history of trauma to the eye. 

Treatment of Synechiae in Cats

Synechiae are usually managed either medically or surgically. 

Medically, treatment is centered around two goals: 

1. Managing any existing underlying conditions that led to the synechiae formation. 
2. Preventing further inappropriate adhesion of the iris to other structures in the eye. 

Affected cats with concurrent uveitis are often treated with anti-inflammatory medications. 

Steroid eye drops may be prescribed, such as prednisolone acetate 1%, or non-steroidal anti-inflammatory eye drops, such as diclofenac 0.1% or ketorolac 0.5%, depending on the cause and condition of the eye. 

Eye drops that dilate the pupil, such as atropine, may be prescribed to help prevent or break down posterior synechiae and relieve pain associated with uveitis. 

If the underlying inflammation is immune-mediated or severe enough to require systemic treatment, a veterinarian may prescribe a systemic corticosteroid such as prednisolone pills or transdermal cream.   

If underlying infections are present, they will be treated accordingly, often with antibiotic, antiviral, or antifungal medications, depending on the specific infection. 

Sometimes surgery is indicated in cats affected by synechiae. A veterinary ophthalmologist may use a laser or scalpel to carefully detach synechiae. 

If there is concern for intraocular cancer or if severe secondary glaucoma or chronic eye pain cannot be managed medically, your veterinarian may recommend enucleation, which is surgical removal of the eye.   

Recovery and Management of Synechiae in Cats

Recovery following medical management of synechiae in cats usually entails getting a good rhythm and routine for eye medications. 

Depending on the underlying cause of your cat’s synechiae, recovery may require long-term eye medications that are given regularly for weeks, months, or their entire life. If oral medications are prescribed, consider the use of pill pockets or a pet piller to make medicating easier.   

If surgery was performed, initial healing may take about 10–14 days, depending on the procedure and your veterinarian’s instructions. 

During the recovery period, it is important that your cat not be allowed to rub their affected eye or face. The use of a recovery cone is necessary. 

Your veterinarian may recommend a cold pack wrapped in a soft towel for short periods after some procedures, such as enucleation, to help with swelling and comfort. 

Follow your veterinarian’s specific postoperative instructions. 

Prevention of Synechiae in Cats

The best way to reduce your cat’s risk of developing synechiae is to treat eye conditions promptly before secondary adhesions form. If you notice any changes in the way your cat’s eyes look, such as squinting or drainage, schedule an appointment with a veterinarian as soon as possible. 

Minimizing your cat’s exposure to stray or unfamiliar cats may also reduce exposure to some infectious diseases and traumatic injuries that can lead to uveitis and increase their risk of developing synechiae. 

Cats that roam outdoors and interact with unfamiliar cats may have greater exposure to FeLV, FIV, bite wounds, and other infections or injuries associated with uveitis. 

Trauma is also more likely to occur after a cat fight or if your cat has interacted with  unfamiliar cats.