Overview of Cats with a Red Eye
Red eye is a non-specific sign of inflammation or infection. It may be seen with diseases of the external eyelids, third eyelid, conjunctiva, cornea, and sclera. It may also occur with inflammation of the structures inside the eye, with glaucoma (high pressure within the eye) or with certain diseases of the orbit (eye socket). Either one or both eyes can become red, depending upon the cause of the problem.
Eyes become reddened when blood vessels of the conjunctiva (the pink lining of the eyeball and eyelids), sclera (white covering of the eye), or cornea (clear surface of the eye) become enlarged or more numerous.
What to Watch For
Redness of the eye or structures around the eye
Squinting, increased blinking, holding the eye closed
Pawing or rubbing at the eye
Possible decrease in vision or blindness
Possible cloudiness of the eye
Tearing or discharge from the eye
Possible systemic signs if the redness is associated with some sort of illness
Diagnosis of Red Eyes in Cats
Veterinary care includes tests to diagnose the condition causing the red eye and to define subsequent treatment. Your veterinarian will do a complete medical history and physical examination to try to determine if the problem involves only the eye(s) or if other changes are present in the animal.
A complete ophthalmic examination is required to determine the source of the redness and whether it involves inflammation of the external structures of the eye or the internal structures. Your veterinarian may refer your cat to a veterinary ophthalmologist for further evaluation using specialized instrumentation. The following tests may be performed during the eye examination:
Schirmer tear test to measure tear production
Fluorescein staining of the cornea to check for ulcers
Tonometry to measure the pressure within the eye
Examination of the interior of the eye under magnification
Taking scrapings of inflamed tissues (such as conjunctiva and cornea) for cytologic studies to determine the type of inflammation present
Examination of scrapings of the eyelids to look for parasites
Submission of samples for culturing bacteria and other agents
Biopsy of masses around the eye
Other tests may include:
A complete blood count and biochemistry profile if any systemic signs are present
Blood testing for the tick borne rickettsial and bacterial infections, for fungal infections and parasitic conditions, if the red eye is related to inflammation of the interior of the eye
X-rays of the chest and abdomen if an underlying systemic illness is suspected
Treatment of the Red Eye in Cats
The goal of therapy is to decrease any inflammation present and to address the underlying cause. It is very important that the cause of the inflammation or infection be diagnosed, so that specific treatment can be started.
Anti-inflammatory medication. The are two basic classes of topical anti-inflammatory medications that may be used to treat red eyes: nonsteroidal anti-inflammatory drugs and topical corticosteroids. These medications are not indicated when corneal ulcers are present or during active herpesvirus infections, and must be chosen based on the underlying ocular condition.
The nonsteroidal anti-inflammatory drugs (NSAIDs) are agents similar in action to ibuprofen. They are beneficial in some forms of red eye and not in others. They are less potent than the topical corticosteroids.
The topical corticosteroids are used most commonly for conjunctivitis, anterior uveitis and some forms of corneal inflammation. A number of these drugs exist and have varying degrees of potency.
Systemic anti-inflammatory medications. Occasionally systemic anti-inflammatory medications are used in conjunction with topical medications. These include antihistamines for the treatment of allergic conditions, oral NSAIDs to alleviate pain and inflammation inside the eye, and oral corticosteroids. The use of these products depends on the underlying cause of the red eye. It is important to note that systemic corticosteroids should not be used if infectious diseases (such as feline herpesvirus, fungal infections, etc.) are the source of the redness.
An Elizabethan collar may be applied to prevent rubbing or pawing at the eye.
An antibiotic or antiviral eye medication may be administered to treat or prevent infection.
Lubricant eye drops or ointment are sometimes given to protect the surface of the eye.
Swollen tissues may respond to warm, wet compresses.
Other treatments may be administered, depending upon the underlying cause.
Home Care
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up is important and may include the following:
Administer prescribed medications as directed and alert your veterinarian if you are experiencing problems treating your pet.
Ensure that your pet does not rub at the eye and cause more serious injury. If an Elizabethan collar is provided, have your pet wear it at all times.
Observe the eye closely. Signs that may indicate a worsening condition include more obvious redness, increased or altered discharge, pain or loss of vision. Blindness in just one eye may not be obvious, because the animal may behave normally when only one eye is affected.
In-depth Information on Cats with a Red Eye
It is important to differentiate whether the engorged blood vessels that cause an eye to appear “red” are superficial or deep. Engorgement of superficial vessels indicates surface irritation, while reddening of deep blood vessels represents inflammation of more important ocular structures. Deep inflammation is more frequently associated with vision-threatening disease.
Red eye due to conjunctivitis is relatively common and does not require emergency treatment. However, when the redness reflects inflammation of deeper structures, particularly if the eye is painful, then your veterinarian should be consulted promptly.
Causes of Red Eye in Cats
conjunctivitis is one of the more common causes of red eye and, in cats is typically due to infectious agents such as Herpesvirus or Chlamydia psittaci.
Conjunctivitis is associated with engorgement (filling up of fluid) of the smaller, superficial blood vessels of the conjunctiva and will appear different to your veterinarian than engorgement of the deeper (episcleral) blood vessels. Determining the cause of the conjunctivitis and beginning treatment will usually provide significant reduction of inflammation and redness. This is not a vision-threatening disease.
Blepharitis is inflammation of the eyelids. This can be part of a more widespread dermatitis (skin inflammation) or can be localized to the eyelids only. Multiple causes are possible including allergy, parasitic, fungal or bacterial infections and immune-mediated inflammation. Blepharitis causes red eye by inflammation of the adjacent conjunctiva. Concurrent treatment of the conjunctival and skin inflammation is necessary.
Keratitis refers to inflammation of the cornea and is a frequent cause of reddening of the surrounding blood vessels. With more serious or chronic keratitis, blood vessels may begin to encroach (intrude or invade) on the cornea from the surrounding sclera or conjunctiva. In general, keratitis is a more serious diagnosis than conjunctivitis. You should be suspicious of corneal involvement if your pet is showing signs of discomfort such as squinting. Your veterinarian will look for other signs of corneal involvement such as ulceration or opacity of the cornea.
Scleritis is a rare diagnosis. This form of red eye involves the deep blood vessels and usually reflects an altered immune response to the animal’s own sclera. Diagnosis and treatment of this syndrome can be quite challenging and your local veterinarian may recommend referral to a veterinary ophthalmologist.
Uveitis refers to inflammation of the inner vascular layer of the eye including the colored iris and related structures. This is a serious and potentially vision-threatening disease. Uveitis may even indicate that your pet has inflammation of structures within the body other than the eye, especially if both eyes are involved. In this case your veterinarian may recommend some blood tests or radiographs (X-rays) to assess your pet’s health further. Uveitis produces engorgement of the deep blood vessels and is frequently painful. Your animal may appear generally depressed. More serious signs, such as these, warrant an urgent visit to your veterinarian and potentially referral to a veterinary ophthalmologist.
Glaucoma refers to an increase in intraocular pressure (pressure within the eye). This diagnosis is made after tonometry (measurement of intraocular pressure) is performed on your pet. This is a painful disease that will cause engorgement of the deep blood vessels around the eye. If intraocular pressure is excessive or remains elevated for long periods, vision is lost. Ultimately, if untreated, glaucoma causes the eye to stretch and enlarge. This disease can be challenging to treat. Frequently, your veterinarian will recommend referral to a veterinary ophthalmologist for management of glaucoma.
Diagnosis In-depth
Veterinary care includes diagnostic tests to determine the underlying cause of the red eye and guide subsequent treatment. Your veterinarian will do a complete medical history and physical examination to determine if the problem involves only the eye(s) or whether other changes are present in the animal.
A complete ophthalmic examination is required to determine the source of the redness and whether it involves inflammation of the external structures of the eye or the internal structures. Your veterinarian may refer your cat to a veterinary ophthalmologist for further evaluation using specialized instrumentation. The following tests may be performed during the eye examination:
Schirmer tear test to measure tear production
Fluorescein staining of the cornea to check for ulcers
Tonometry to measure the pressure within the eye
Examination of the interior of the eye under magnification
Taking scrapings of inflamed tissues (such as conjunctiva and cornea) for cytologic studies to determine the type of inflammation present
Examination of scrapings of the eyelids to look for parasites
Submission of samples for culturing bacteria and other agents
Biopsy of masses around the eye
If uveitis is the suspected diagnosis or if your pet appears unwell, then further tests are indicated to identify diseases that are systemic (involve other systems). Common tests include a complete blood count, biochemistry profile, serum tests for tick borne diseases, systemic fungal infections, and toxoplasmosis, and possibly X-rays of the chest and abdomen.
Treatment In-depth
Exact treatment requires establishment of a diagnosis.
An Elizabethan collar may be applied to protect the eye. Ocular inflammation may be irritating and your pet can cause more serious injuries to their eye if they scratch it with their paws, or rub it against carpet or furniture.
Infectious agents can be the cause of conjunctivitis, especially in cats, and can worsen ocular inflammation in all animals. Therefore, your veterinarian may prescribe a topical antibiotic or antiviral medication to treat or prevent infection.
Lubricant eye drops or ointments may be prescribed to reduce the dry feeling associated with some surface eye inflammation or to treat any deficiency in the watery tears (dry eye).
Numerous topical anti-inflammatory preparations can be used to diminish inflammation (redness) in the eye. It is important to reiterate that although they may make the eye appear better, these treatments are non-specific and do not replace treatment of the inciting cause. They can also exacerbate a pre-existing condition or lead to other complications. They should be instituted only upon direction of your veterinarian.
Topical corticosteroids are the most commonly used class of anti-inflammatory agents for non-infectious forms of conjunctivitis, keratitis and anterior uveitis.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are a second class of anti-inflammatory drugs, and may be used sometimes in the presence of certain infections.
Topical antihistamines may be tried to control inflammation associated with allergies, but they frequently contain other products (vessel constricting agents) that can be irritating to animals.
Occasionally systemic anti-inflammatory medications are used in conjunction with topical medications. These include antihistamines for the treatment of allergic conditions, oral NSAIDs to alleviate pain and inflammation inside the eye, and oral corticosteroids. The use of these products depends on the underlying cause of the red eye. It is important to note that systemic corticosteroids should not be used if infectious diseases such as feline herpesvirus or fungal infections are the source of the redness.
Swollen tissues may respond to warm, wet compresses.
Other treatments may be administered, depending upon the underlying cause.
