Introduction
Eye infections are a common health problem for cats and can be caused by a variety of factors like bacteria, viruses, fungi, foreign objects, anatomical defects, allergies, or trauma.
The most common symptoms of an eye infection in cats include: swollen eyelids, redness, cloudy eyes, excessive tearing or discharge, squinting or blinking, pawing at the eyes, sensitivity to light, and crusty eyes. Eye infections can range from mild to severe. Mild cases may clear up on their own, while chronic or severe infections require veterinary treatment.
Left untreated, eye infections in cats can cause permanent damage and blindness. So it’s important for cat owners to watch for eye infection symptoms and seek prompt veterinary care. Eye infections in cats are very treatable if caught early. Treatment may include antibiotic eye drops or ointment, antiviral medication, anti-fungal medication, flushing the eye, or surgery.
Bacterial Infections
Common bacterial causes of conjunctivitis or eye infections in cats include Chlamydia, Mycoplasma, and Staphylococcus. Bacteria can enter a cat’s eyes through contact with an infected animal or environment. Cats with weakened immune systems are more susceptible to bacterial infections.
Symptoms of a bacterial eye infection include redness, swelling, excessive tearing, white or yellow discharge, squinting, and crusty eyes. The infection may affect one or both eyes. In severe cases, ulcers, corneal scarring, or blindness can occur if left untreated.
According to the VCA Animal Hospitals, infectious agents like bacteria are the most common causes of conjunctivitis in cats [1]. Antibiotics such as azithromycin may be prescribed by a veterinarian to treat underlying bacterial infections [2].
Viral Infections
Common viral causes of eye infections in cats include feline herpesvirus and calicivirus.
The feline herpesvirus, also known as feline rhinotracheitis virus, is one of the most common viral causes of conjunctivitis and keratitis in cats according to the VCA Hospitals https://vcahospitals.com/know-your-pet/conjunctivitis-feline-herpes-viral. It is extremely contagious and spreads through direct contact between cats, contact with contaminated surfaces or shared resources, or through tiny aerosol droplets. The virus first infects the upper respiratory tract and can then spread to the eyes.
Symptoms of viral eye infections include inflammation of the conjunctiva (conjunctivitis), eye discharge, sores or ulcers on the cornea (keratitis), and swelling of the eyelids or third eyelid. Viral infections can lead to serious complications like corneal scarring and vision loss if left untreated.
Fungal Infections
Fungal infections are less common but still possible causes of eye infections in cats. Certain fungi like Aspergillus, Candida, or Cryptococcus can infect the eyes and cause symptoms like redness, discharge, corneal ulcers, and vision loss. Fungal infections often start in the nose or sinuses and spread to the eyes via the tear ducts. Cats with weakened immune systems are more prone to fungal eye infections. Diagnosis involves culture tests and imaging. Treatment consists of antifungal medications, sometimes given long-term to fully resolve the infection.
Foreign Objects
A common way that cats can develop eye infections is by getting foreign objects, such as dirt, debris, or plant material lodged in their eyes. These objects can scratch or irritate the cornea or conjunctiva. According to the Lort Smith animal hospital, the most common foreign bodies affecting cat eyes include “plant material, grass seeds and dirt and dust particles.” https://lortsmith.com/need-help-now/cat/injury-trauma/foreign-body-in-the-eye/
When a foreign object gets into the eye, it can cause inflammation, discharge, squinting, swelling, and redness. The cat may paw at the eye excessively trying to dislodge the object. In severe cases, corneal scratches or ulcers can occur, causing significant pain and impaired vision. Cats that spend time outdoors hunting prey or digging in soil are especially prone to getting foreign material in their eyes.
It’s important not to try removing a foreign object yourself, as this can worsen the damage. Instead, seek prompt veterinary attention so the eye can be properly flushed, numbed, and examined under a slit lamp to locate and remove any debris. Leaving a foreign body untreated can lead to a serious eye infection. With quick treatment, most cats recover fully. However, corneal ulcers may require medication, ointments, or in some cases, surgery to heal completely and restore vision.
Anatomical Defects
Cats can be born with anatomical defects in their eyes that can lead to infections and other problems. Common birth defects include entropion, where the eyelid rolls inward, and ectropion, where the eyelid droops outward. These defects cause the eyelids to rub against the eye, leading to irritation, inflammation, and potential infections.
Entropion is the most common eyelid abnormality in cats, affecting the lower lid more often than the upper lid. Friction from entropion can cause corneal ulcers and scarring as well as conjunctivitis. Surgery to remove a section of eyelid skin may be necessary to correct the defect.
Ectropion, where the eyelid sags and exposes the inner eyelid surface, is also common in certain breeds like Persians. This can lead to dry eye, conjunctivitis, and corneal ulcers from lack of lubrication and protection. Minor cases can be managed with eye medications, but surgery may be required for severe ectropion.
Cats can also be born with defective tear ducts, extra eyelashes, or small eyes (micropthalmia). These conditions require management by a veterinary ophthalmologist to prevent complications like chronic eye infections.
Allergies
Allergies are a common cause of eye infections and irritation in cats. Cats can develop allergies to various allergens in their environment including pollen, dust mites, molds, and even certain foods. These allergens can trigger an immune response that leads to itching, swelling, and discharge from the eyes.
Some common household allergens that may irritate a cat’s eyes include dust and pollen. Dust contains microscopic particles that cats can be sensitive to like dust mites and their feces. Pollen from plants, trees, and grass can also trigger ocular allergies in cats when they inhale or come into contact with it. Mold spores in the home from damp areas like basements can also lead to eye irritation if a cat has a mold allergy.
Cats can also develop food allergies that manifest as eye symptoms. Allergies to ingredients like beef, dairy, chicken, or fish can cause itchy, red, and watery eyes in cats. Identifying and eliminating the allergenic food from the diet is key to treating this type of ocular allergy.
Allergic eye conditions like conjunctivitis will usually involve discharge, redness, itching, swelling, and squinting of the eyes. Some cats may even scratch at their eyes excessively due to the irritation. To treat allergic eye issues in cats, identifying and removing the allergen source is recommended along with medication from a veterinarian like antihistamines or corticosteroids to reduce inflammation and itching.
Trauma
Cats can experience eye trauma from scratches, bites, or blunt force that may introduce infection. Common causes of eye trauma include fights with other cats, falls, sharp objects like sticks or thorns, getting hit by a car, or playing roughly.
Scratches are a major source of eye injuries in cats. Cat fights frequently lead to scratches on the eye from another cat’s claws. These scratches can allow bacteria into the eye and cause infections like conjunctivitis. Bites near the eye from other animals can also introduce bacteria and lead to infection.
Blunt force trauma like banging into furniture or getting hit by a car can rupture blood vessels in the eye. This rupture causes bleeding in the anterior chamber of the eye between the cornea and iris. The blood is a breeding ground for bacteria which can lead to infection and inflammation. Trauma can also cause the lens to become dislocated or the retina to detach, leading to vision problems.
Cats may show symptoms like eye discharge, redness, swelling, squinting, sensitivity to light, and excessive blinking or tearing. Any eye trauma should be evaluated promptly by a vet to prevent infection and treat any damage before it worsens. Vets may prescribe antibiotic eye drops or ointments along with medications to relieve pain and inflammation.
Diagnosis
To diagnose an eye infection in cats, the vet will first perform a comprehensive physical exam and take the cat’s full medical history. They will examine the eyes closely for any discharge, redness, swelling or other abnormalities. Common diagnostic tests may include:
Fluorescein staining – drops are applied to the eye to detect ulcers or scratches on the cornea. These areas will glow green under a special light.
Schirmer tear test – measures tear production by placing a special strip in the eyelid pocket. Decreased tear production can indicate certain infections.
Tonometry – tests pressure inside the eye which can be elevated with some infections.
Cytology – examining a sample of discharge under a microscope to look for bacteria, fungi or abnormal cells.
Viral culture – identifying a specific virus from a swab sample of the eye or nose.
To identify the type of infection, the vet will analyze the examination findings, discharge characteristics, and results of any lab tests. Bacterial infections tend to produce thick, opaque discharge while viral infections cause more watery discharge.
Treatment
Treatment for a cat’s eye infection depends on the cause and severity. Mild infections may resolve on their own, but most require veterinary treatment. Common treatments include:
Antibiotics: Broad-spectrum topical antibiotic drops or ointments like Terramycin or Vetropolycin are often prescribed. Oral antibiotics may be given for severe bacterial infections. Common antibiotics used include doxycycline, amoxicillin, and cephalosporins.[1]
Antivirals: Antiviral eye medications may be prescribed for viral infections like feline herpesvirus. These help control the infection and reduce symptoms.
Antifungals: Fungal eye infections are treated with topical antifungal drops or ointments containing medications like miconazole or natamycin.
Steroids: Steroid eye drops help reduce inflammation and irritation. They are often prescribed along with antibiotics or antivirals.
Surgery: Surgery may be needed to remove foreign objects, drain abscesses, or correct anatomical defects contributing to recurrent infections.
Severely infected eyes may need flushing under anesthesia to properly clean them. In rare cases, partial or complete surgical removal of the eye (enucleation) is required.
With prompt veterinary treatment, most cat eye infections can be cured or controlled. But neglected infections can cause permanent eye damage or blindness.
[1] https://www.memphisveterinaryspecialists.com/site/blog-cordova/2021/01/15/treatment-for-eye-infections-in-cats-antibiotics-and-more
