# Why Is My Cat having bloodshot eyes? Uveitis Glaucoma and Trauma Guide ## Key Takeaways - Redness in a cat's eye is a symptom, not a disease, indicating inflammation or increased intraocular pressure (IOP), with uveitis, glaucoma, and trauma being the most common serious causes requiring immediate veterinary attention. - Uveitis, inflammation of the uveal tract, is often secondary to systemic infections (FeLV, FIV, FIP, toxoplasmosis), immune-mediated disease, or cancer, presenting with redness, miosis, and a cloudy eye, and can lead to secondary glaucoma. - Glaucoma, characterized by elevated IOP due to impaired aqueous humor drainage, is typically secondary to uveitis or trauma in cats, causing severe pain, corneal edema, mydriasis, and potential irreversible optic nerve damage. - Trauma, from cat fights, blunt force, or foreign bodies, presents with variable signs including redness, swelling, bruising, visible wounds, or corneal ulcers, necessitating prompt diagnosis via fluorescein staining and tonometry. - Veterinary diagnosis relies on ophthalmic examination, tonometry to measure IOP, fluorescein staining for corneal integrity, and often systemic diagnostics (blood tests, blood pressure) to identify underlying causes, particularly for uveitis. - Immediate veterinary care is critical; home remedies and human eye drops are contraindicated, and prompt treatment for uveitis (anti-inflammatories, atropine), glaucoma (pressure-lowering agents), or trauma (surgical repair, antibiotics) is essential to preserve vision and comfort. --- If your [cat](/knowledge/veterinary-medicine/clinical-methods/cat) has bloodshot eyes, the redness is a sign of inflammation or increased pressure inside the eye, not a condition itself. The three most common and serious causes are uveitis (inflammation inside the eye), glaucoma (increased fluid pressure), and trauma (physical injury). This guide explains each cause, how veterinarians tell them apart, and what you should do right away. **Owner Triage Summary:** Bloodshot eyes in cats are always a reason for a veterinary visit, often on an emergency basis. Do not wait to see if it clears up. While you arrange transport, keep your cat in a dark, quiet room and do not touch or rub the eye. Do not administer any human eye drops, especially those containing steroids, because they can worsen certain infections or ulcers. If your cat is squinting, pawing at the eye, or the eye looks cloudy, treat this as an emergency. ## At a Glance: Uveitis, Glaucoma, and Trauma This table provides a quick comparison. Your veterinarian will make the definitive diagnosis. | Feature | Uveitis (Inflammation) | Glaucoma (High Pressure) | Trauma (Injury) | | :--- | :--- | :--- | :--- | | **Core Problem** | Inflammation of the inner vascular layer (uvea) | Inadequate drainage of aqueous humor causing increased intraocular pressure | Physical damage to the eye or surrounding structures | | **Typical Signs** | Redness, squinting, tearing, a constricted pupil, a cloudy or dull eye, and sometimes a visibly swollen iris | Redness, a dilated or fixed pupil, a cloudy or steamy cornea, severe pain, and a visibly enlarged eyeball (buphthalmos) | Redness, swelling of the eyelids, bruising, a visible wound, bleeding, or a change in pupil size | | **Pupil Size** | Often constricted (small) | Often dilated (large) or unresponsive | Variable, depending on the injury | | **Pain Level** | Moderate to severe | Severe, often described as a deep headache | Variable, from mild to severe | | **Vision Threat** | High, can lead to glaucoma, cataracts, or retinal detachment | High, causes irreversible damage to the optic nerve and retina | High, depending on the severity and location of the injury | | **Common Causes** | Infections (viral, bacterial, fungal, parasitic), immune-mediated disease, cancer, or trauma | Primary (rare, breed-related) or secondary to uveitis, trauma, or lens luxation | Cat fights, blunt force, foreign bodies, or penetrating wounds | ## Understanding the Feline Eye: Anatomy and Physiology To understand why an eye turns red, it helps to know its basic structure. The eye is a fluid-filled sphere. The outer layer includes the clear cornea and the white sclera. The middle layer is the uvea, which is rich in blood vessels and has three parts: the iris (the colored part), the ciliary body (which produces fluid), and the choroid (which supplies blood to the retina). The inner layer is the retina, which detects light. Redness, medically termed hyperemia, occurs when the small blood vessels on the surface of the eye (conjunctival vessels) or the deeper vessels within the eye (episcleral vessels) dilate and fill with blood. This is a universal response to irritation, inflammation, or injury. The eye also maintains a constant internal pressure, called intraocular pressure (IOP), to keep its shape. A clear fluid called aqueous humor is produced by the ciliary body and drains through a meshwork at the angle where the iris and cornea meet. If this drainage system becomes blocked, pressure builds up, leading to glaucoma. ## Why Is My Cat Having Bloodshot Eyes? The Three Main Causes When a cat presents with a red eye, a veterinarian will systematically rule out these three primary conditions, as they require very different treatments. ### Uveitis: The Most Common Cause of Red Eyes in Cats Uveitis is inflammation of the uveal tract. It is arguably the most common cause of a red eye in cats and is a complex condition with many potential underlying triggers. **Pathophysiology:** Inflammation causes the blood vessels in the uvea to leak fluid and white blood cells into the eye. This makes the eye appear red and cloudy. The inflammation can also cause the pupil to constrict (miosis) and can affect the ciliary body's ability to produce fluid, often leading to a temporarily low intraocular pressure. **Causes and Differentials:** In cats, uveitis is frequently a sign of an underlying systemic disease. The most significant causes include: - **Infectious Diseases:** [Feline leukemia virus](/knowledge/viruses/pet-viruses/feline-leukemia-virus) (FeLV), [feline immunodeficiency virus](/knowledge/viruses/pet-viruses/feline-immunodeficiency-virus) (FIV), feline infectious peritonitis (FIP), toxoplasmosis, and fungal infections like histoplasmosis are all well-documented causes of uveitis. - **Immune-Mediated Disease:** The body's immune system can mistakenly attack the uvea, leading to inflammation without an identifiable infectious agent. - **Trauma:** Any blunt or penetrating injury to the eye can trigger uveitis as a secondary response. - **Cancer:** Primary tumors of the eye, such as melanoma or lymphoma, can cause uveitis. Lymphoma is a particularly important cause in cats. - **Metabolic Disease:** High blood pressure (hypertension) can cause bleeding and inflammation within the eye. **Clinical Signs:** A cat with uveitis will often have a red eye, excessive tearing (epiphora), squinting (blepharospasm), and a constricted pupil. The iris may appear dull, swollen, or change color. The cornea may look cloudy or hazy due to fluid buildup in its layers. The eye may feel softer than normal due to decreased fluid production. ### Glaucoma: A Painful Emergency Glaucoma is a condition characterized by increased intraocular pressure (IOP). It is a painful and vision-threatening disease that requires immediate veterinary attention. **Pathophysiology:** Glaucoma occurs when the aqueous humor cannot drain properly from the eye. This can be a primary problem (a defect in the drainage angle, which is rare in cats) or, more commonly, a secondary problem where the drainage angle is blocked by another condition. **Causes and Differentials:** In cats, glaucoma is almost always secondary to another disease process. - **Secondary to Uveitis:** This is the most common cause. Inflammatory debris and scar tissue can physically block the drainage angle, preventing fluid from leaving the eye. - **Secondary to Trauma:** Damage to the lens or internal structures can disrupt normal fluid flow. - **Secondary to Lens Luxation:** If the lens moves out of its normal position, it can physically block the pupil or the drainage angle. - **Primary Glaucoma:** This is an inherited condition, but it is uncommon in domestic cats compared to dogs. **Clinical Signs:** The eye is often severely red and painful. The cornea may appear cloudy or bluish (edema). The pupil may be dilated and unresponsive to light. As the pressure increases, the eyeball itself may enlarge, a condition called buphthalmos. This is a late sign and indicates that the eye has sustained significant, likely irreversible internal damage. ### Trauma: Direct Injury to the Eye Trauma is a common cause of a red eye, especially in cats that go outdoors or live in multi-cat households. **Causes and Differentials:** - **Cat Fights:** Bite wounds and scratches can directly injure the cornea, sclera, or eyelids. They can also introduce bacteria into the eye, leading to a severe infection. - **Blunt Force:** Being hit by a car or a blunt object can cause internal bleeding (hyphema) or damage to the retina and optic nerve. - **Foreign Bodies:** Grass seeds, plant material, or small objects can become lodged under the eyelid or penetrate the cornea. - **Chemical Irritation:** Exposure to household chemicals can cause severe corneal burns and conjunctivitis. **Clinical Signs:** Signs are variable and depend on the type and severity of the injury. They can include redness, swelling of the eyelids (chemosis), bruising, bleeding, a visible corneal ulcer or laceration, squinting, and a change in pupil size or shape. A prolapsed (dislocated) eyeball is a severe form of trauma. ## Risk Factors and Predispositions Several factors can increase a cat's risk for these conditions. - **Lifestyle:** Outdoor cats have a significantly higher risk of trauma from fights and accidents. - **Infectious Disease Status:** Cats infected with FeLV, FIV, or FIP are at a higher risk of developing uveitis. - **Age:** While any age can be affected, older cats are more prone to systemic diseases like hypertension and cancer that can cause uveitis or secondary glaucoma. - **Breed:** While primary glaucoma is rare, it can occur in some breeds. However, breed is not a reliable predictor for the common secondary forms. Your veterinarian will base their diagnosis on clinical findings, not breed alone. ## Veterinary Examination and Diagnostics A thorough veterinary examination is essential. The veterinarian will first perform a physical exam and then focus on the eyes. They will need to differentiate between uveitis, glaucoma, and trauma, as the treatments are opposite. For example, treating glaucoma involves lowering pressure, while treating uveitis often involves reducing inflammation, and some glaucoma medications are contraindicated in uveitis. **Key Diagnostic Tests:** 1. **Ophthalmic Examination:** The veterinarian will use a bright light and a magnifying lens to examine the eye's structures in detail. 2. **Schirmer Tear Test (STT):** This test measures tear production to rule out dry eye (keratoconjunctivitis sicca), which can also cause redness. 3. **Fluorescein Stain Test:** A dye is applied to the eye to check for corneal ulcers or scratches. This is a critical test for trauma. 4. **Tonometry:** This test measures the intraocular pressure (IOP). A small, pen-like device is gently placed against the cornea. This is the definitive test for glaucoma. 5. **Ophthalmoscopy:** After dilating the pupil, the veterinarian can examine the lens, retina, and optic nerve for signs of inflammation, bleeding, or detachment. **Additional Systemic Testing:** Because uveitis is often a sign of a systemic disease, your veterinarian may recommend blood tests, including a complete blood count, biochemistry profile, and tests for FeLV, FIV, toxoplasmosis, and other infectious agents. Blood pressure measurement is also crucial to rule out hypertension. ## Evidence-Based Management and Treatment Treatment is highly specific to the diagnosis. Never attempt to treat a red eye at home without a veterinary diagnosis. ### Treatment for Uveitis The goals are to reduce inflammation, relieve pain, and treat the underlying cause. - **Topical Anti-Inflammatories:** Corticosteroid eye drops are often prescribed to reduce inflammation. However, they are strictly contraindicated if a corneal ulcer is present, as they can delay healing and worsen infection. - **Atropine:** This medication dilates the pupil and helps relieve the painful spasms of the ciliary muscle. - **Systemic Medications:** If an infectious cause is found, specific treatments like antibiotics, antifungals, or antiviral drugs will be prescribed. Treatment for underlying conditions like hypertension or cancer is also essential. - **Pain Relief:** Oral pain medications may be given to keep your cat comfortable. ### Treatment for Glaucoma Glaucoma is an emergency. The goal is to lower the IOP rapidly to prevent irreversible damage to the optic nerve. - **Osmotic Agents:** In a hospital setting, intravenous medications like mannitol may be used to rapidly draw fluid out of the eye. - **Topical Medications:** Medications like prostaglandin analogues (e.g., latanoprost) and carbonic anhydrase inhibitors (e.g., dorzolamide) are used to increase fluid drainage and decrease fluid production. - **Surgery:** In cases that do not respond to medication, surgical options may be considered to create a new drainage pathway or to destroy the fluid-producing cells. - **Enucleation:** If the eye is blind and painful, surgical removal of the eye (enucleation) may be the most humane option to relieve suffering. ### Treatment for Trauma Treatment depends on the specific injury. - **Corneal Ulcers:** Treated with topical antibiotics and pain relief. Surgery may be needed for deep ulcers. - **Lacerations:** May require surgical repair. - **Hyphema (Bleeding in the Eye):** Treated with rest and anti-inflammatory medications. - **Foreign Bodies:** Removed surgically if necessary. - **Prolapsed Eye:** Requires immediate surgical replacement. ## Unsafe Home Remedies and What to Avoid Your good intentions can cause serious harm. Avoid the following: - **Human Eye Drops:** Do not use Visine, artificial tears, or any other human eye drops. They are not formulated for cats and can be toxic or ineffective. Most critically, never use human steroid drops (like hydrocortisone) as they can worsen a corneal ulcer. - **Over-the-Counter Pet Eye Drops:** Many of these are not effective for the serious conditions discussed here and can delay proper treatment. - **Herbal Remedies:** Do not apply any herbal teas, oils, or washes to the eye. They are not sterile and can introduce bacteria or cause severe irritation. - **Rubbing the Eye:** Do not rub or massage the eye. This can cause further damage, especially if there is a corneal ulcer or a penetrating injury. - **Attempting to Flush the Eye:** Unless a veterinarian instructs you to flush the eye with a specific sterile saline solution, do not attempt to rinse it yourself. ## Prevention and Long-Term Prognosis **Prevention:** - **Keep Cats Indoors:** This is the single most effective way to prevent trauma from fights and accidents. - **Vaccination:** Keep your cat's vaccinations up to date to reduce the risk of infectious diseases like FPV ([feline panleukopenia](/knowledge/veterinary-medicine/viral-diseases/feline-panleukopenia), a cause of uveitis in kittens). - **Regular Veterinary Checkups:** Annual or semi-annual exams can help detect early signs of systemic diseases like hypertension before they cause eye problems. **Prognosis:** - **Uveitis:** The prognosis depends entirely on the underlying cause. If the cause is treatable, the inflammation can often be controlled. However, chronic uveitis can lead to secondary glaucoma, cataracts, and permanent vision loss. - **Glaucoma:** The prognosis for vision is poor if the pressure is not controlled quickly. Once vision is lost, it is usually permanent. The goal of treatment is often to maintain comfort and a good quality of life. - **Trauma:** The prognosis varies widely. Minor corneal ulcers heal well with treatment. Severe injuries, like a ruptured globe or a prolapsed eye, have a guarded to poor prognosis for saving the eye. ## Limitations and When to Contact a Veterinarian This guide provides general veterinary information and is not a substitute for a professional diagnosis. The information presented here cannot predict the specific cause of your cat's red eye. Breed-level information is particularly unreliable for predicting these conditions, as the most common causes (infection, trauma, systemic disease) are not breed-specific. Only a hands-on veterinary examination, including tonometry and other diagnostics, can determine if your cat has uveitis, glaucoma, trauma, or another condition. **Contact your veterinarian or an emergency veterinary clinic immediately if your cat has any of the following:** - A red eye that persists for more than a few hours. - Squinting, excessive blinking, or pawing at the eye. - A cloudy, blue, or hazy cornea. - A change in pupil size (either constricted or dilated). - Bleeding from the eye or visible wounds. - An obviously swollen or enlarged eyeball. - Signs of systemic illness, such as lethargy, loss of appetite, or fever. - Any sudden change in vision or bumping into objects. Do not wait. Eye conditions are painful and can lead to permanent blindness quickly. ## The Clinical Significance of Redness: Conjunctival Versus Episcleral Injection When you look at your cat's red eye, the pattern of redness itself carries diagnostic information that your veterinarian will interpret carefully. Redness is not uniform, and the location and character of the blood vessels involved can point toward a specific category of disease before any instruments are used. Conjunctival hyperemia refers to redness of the thin, transparent membrane that lines the eyelids and covers the front part of the sclera. This type of redness tends to be bright red, involves the vessels that are visible on the surface, and often affects the inner lining of the eyelids as well. Conjunctival hyperemia is commonly seen with surface conditions such as conjunctivitis, dry eye, or mild irritation. The vessels appear fine, branching, and they move with the conjunctiva when you gently manipulate the eyelid. Episcleral injection, by contrast, involves the deeper blood vessels that lie just beneath the conjunctiva, over the sclera itself. This redness appears as a darker, more violaceous or brick-red color, and the vessels are straighter, larger, and do not move as freely over the surface. Episcleral injection is a hallmark of deeper intraocular disease, including uveitis and glaucoma. When a veterinarian sees this pattern, they immediately shift their focus from surface conditions to the interior of the eye. The distinction matters because it changes the urgency and the diagnostic plan. A cat with purely conjunctival hyperemia from a mild irritant may not require the same aggressive workup as a cat with episcleral injection suggesting uveitis or glaucoma. However, in practice, many cats present with a mixed pattern, and the redness can be accompanied by other signs such as discharge, squinting, or changes in the appearance of the cornea. This is why a hands-on examination is non-negotiable. The pattern of redness is one piece of a larger puzzle that includes pupil size, corneal clarity, intraocular pressure, and the results of a fluorescein stain test. Another important observation is the difference between a unilateral and bilateral presentation. A single red eye is more suggestive of trauma, a foreign body, or a localized problem such as a corneal ulcer. Bilateral redness raises the suspicion of a systemic process, such as an infectious disease, hypertension, or an immune-mediated condition. Cats with feline herpesvirus, for example, may develop uveitis in one eye initially, but the infection can spread to both eyes over time. Toxoplasmosis and fungal infections frequently cause bilateral disease because the organisms reach the eye through the bloodstream. Your veterinarian will ask whether the redness appeared suddenly or gradually, whether it is confined to one eye, and whether you have noticed any changes in your cat's behavior, appetite, or energy level. ## The Diagnostic Challenge of the Feline Red Eye The red eye in cats presents a unique diagnostic challenge because the clinical signs of uveitis, glaucoma, and trauma overlap considerably. A cat with uveitis may have a cloudy cornea, a constricted pupil, and a soft eye. A cat with glaucoma may have a cloudy cornea, a dilated pupil, and a firm eye. But there are exceptions to every rule. Some cats with uveitis develop secondary glaucoma because the inflammation blocks the drainage angle, and in these cases, the eye may feel firm even though the primary problem is inflammation. Conversely, a cat with early glaucoma may not yet have a visibly enlarged eyeball, and the pupil may still respond sluggishly to light. This overlap is why tonometry is essential. Tonometry measures the intraocular pressure by gently applanating or indenting the cornea with a specialized device. The normal intraocular pressure in cats typically falls within a range that your veterinarian will interpret based on the device used and the cat's individual characteristics. A pressure that is too low can indicate uveitis, because inflammation reduces the production of aqueous humor by the ciliary body. A pressure that is too high indicates glaucoma, because the fluid cannot drain adequately. The numerical value alone does not tell the whole story, but it is a critical data point that helps your veterinarian distinguish between these two conditions. The Schirmer tear test is another routine diagnostic that is often performed before other tests. This test uses a small strip of filter paper placed inside the lower eyelid to measure tear production over one minute. Low tear production suggests keratoconjunctivitis sicca, or dry eye, which can cause redness and discomfort. While dry eye is less common in cats than in dogs, it can occur, especially in association with chronic herpesvirus infection or certain medications. Identifying dry eye is important because it changes the treatment plan. A cat with dry eye needs tear replacement therapy and possibly immune-modulating medication, not anti-inflammatory drops alone. Fluorescein stain testing is performed to evaluate the integrity of the cornea. A small amount of orange dye is applied to the surface of the eye, and then the eye is examined under a cobalt blue light. If the cornea has an ulcer or a scratch, the dye will adhere to the exposed underlying tissue and appear green. This test is critical in any cat with a red eye because corneal ulcers can be present without being obvious to the naked eye. A deep ulcer can progress to a perforation of the globe if not treated promptly. The presence of a corneal ulcer also contraindicates the use of corticosteroid eye drops, which can delay healing and increase the risk of infection. ## Uveitis in Depth: Beyond the Basics Uveitis is not a single disease but a syndrome with many potential causes. The uveal tract, which includes the iris, the ciliary body, and the choroid, is highly vascular and serves as a route for immune cells to enter the eye. When the immune system is activated by an infection, an injury, or a mistaken attack on the body's own tissues, the uvea becomes inflamed. The inflammation can be confined to the front of the eye (anterior uveitis or iritis), the middle of the eye (intermediate uveitis or cyclitis), the back of the eye (posterior uveitis or choroiditis), or it can involve all layers (panuveitis). In cats, anterior uveitis is the most common presentation, but posterior involvement can occur, especially with systemic infections. The clinical signs of uveitis reflect the underlying pathophysiology. The redness is caused by dilation of the episcleral vessels. The constricted pupil, or miosis, occurs because inflammation stimulates the iris sphincter muscle. The cloudy appearance of the eye can result from protein and inflammatory cells leaking into the aqueous humor, which is normally clear. This cloudiness is called aqueous flare, and it is a key finding on ophthalmic examination. The iris itself may appear swollen, dull, or thickened, and in some cases, inflammatory cells can accumulate in the anterior chamber, forming a visible layer called hypopyon. Bleeding into the anterior chamber, called hyphema, can also occur if the inflammation damages blood vessels. The diagnostic workup for uveitis extends beyond the eye. Because infectious and systemic diseases are common underlying causes, your veterinarian will likely recommend blood tests. A complete blood count can reveal anemia, infection, or inflammation. A biochemistry profile evaluates organ function and can detect abnormalities such as elevated globulins, which may suggest chronic infection or immune-mediated disease. Specific tests for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are important because these retroviruses can cause uveitis directly or through associated infections. Testing for toxoplasmosis, feline infectious peritonitis (FIP), and fungal diseases such as histoplasmosis, blastomycosis, and cryptococcosis may also be recommended depending on your cat's lifestyle and geographic location. Blood pressure measurement is a crucial part of the uveitis workup, especially in older cats. Systemic hypertension can cause bleeding within the eye, leading to hyphema and uveitis. The retina can also detach as a result of high blood pressure, causing sudden blindness. Measuring blood pressure is non-invasive and can be performed in the veterinary clinic with a Doppler device or an oscillometric monitor. Identifying and treating hypertension is essential not only for the eye but also for the kidneys, heart, and brain. The treatment of uveitis has two main goals: controlling the inflammation and addressing the underlying cause. Topical corticosteroids are the mainstay of anti-inflammatory therapy, but they are contraindicated if a corneal ulcer is present. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used systemically in some cases, but they must be used with caution in cats because of their effects on the kidneys and gastrointestinal tract. Atropine is often used to dilate the pupil and reduce the painful spasms of the ciliary muscle. However, atropine should be used with caution in cats with glaucoma or a predisposition to glaucoma, because it can increase intraocular pressure by impairing aqueous humor drainage. The prognosis for uveitis depends on the underlying cause and the speed of treatment. Infectious causes can often be treated successfully with appropriate antimicrobial or antifungal therapy. Immune-mediated uveitis may require long-term immunosuppressive treatment. Chronic uveitis can lead to complications such as cataracts, synechiae (adhesions between the iris and the lens or cornea), secondary glaucoma, and retinal detachment. These complications can cause permanent vision loss even if the inflammation itself is controlled. ## Glaucoma in Depth: Mechanisms and Consequences Glaucoma is a condition of elevated intraocular pressure that damages the optic nerve and retina. The pressure rises because the aqueous humor, which is produced continuously by the ciliary body, cannot drain adequately through the iridocorneal angle. In cats, primary glaucoma is rare and is thought to have a genetic basis in some breeds, but the vast majority of feline glaucoma cases are secondary to another disease process. The most common cause of secondary glaucoma in cats is chronic uveitis. Inflammation produces cells, protein, and debris that can clog the drainage angle. Over time, scar tissue can form, permanently obstructing the outflow pathways. Trauma can also cause glaucoma by damaging the lens, the ciliary body, or the drainage angle itself. Lens luxation, in which the lens moves forward into the anterior chamber or backward into the vitreous cavity, can physically block the pupil or the drainage angle. Intraocular tumors, such as melanoma or lymphoma, can also obstruct aqueous humor outflow. The clinical signs of glaucoma are related to the elevated pressure. The eye becomes red due to episcleral vessel dilation. The cornea becomes cloudy because fluid accumulates within its layers, a condition called corneal edema. The pupil may be dilated and unresponsive to light because the pressure damages the iris and the nerves that control pupil size. The eye may be painful, and the cat may squint, paw at the eye, or show behavioral changes such as hiding, decreased appetite, or aggression. As the pressure continues to rise, the eyeball itself may enlarge, a condition called buphthalmos. Buphthalmos is a late sign that indicates the sclera has stretched, and it is associated with irreversible damage to the optic nerve and retina. The diagnosis of glaucoma is confirmed by tonometry. A single elevated reading is sufficient to make the diagnosis, but your veterinarian may repeat the measurement to confirm and to monitor the response to treatment. The normal intraocular pressure in cats is typically lower than in dogs, and your veterinarian will interpret the reading in the context of the other clinical findings. The treatment of glaucoma is directed at lowering the intraocular pressure rapidly to prevent further damage to the optic nerve. In an emergency setting, intravenous osmotic agents such as mannitol may be used to draw fluid out of the eye. Topical medications are the mainstay of long-term management. Prostaglandin analogues such as latanoprost increase aqueous humor outflow through the uveoscleral pathway. Carbonic anhydrase inhibitors such as dorzolamide and brinzolamide decrease aqueous humor production. Beta-blockers such as timolol also reduce aqueous humor production. These medications may be used alone or in combination, and the response to treatment is monitored with repeated tonometry. If medical management fails to control the pressure, surgical options may be considered. These include procedures to create a new drainage pathway, such as a gonioimplant or a cyclodestructive procedure that destroys part of the ciliary body to reduce fluid production. In cases where the eye is blind and painful, enucleation, or surgical removal of the eye, may be the most humane option. Enucleation eliminates the pain and allows the cat to live comfortably without the affected eye. Many cats adapt remarkably well to single-eyed vision, especially if the remaining eye has adequate vision. The prognosis for glaucoma is guarded. Once vision is lost, it is usually permanent because the optic nerve does not regenerate. The goal of treatment is to preserve vision for as long as possible and to maintain comfort. In cats with secondary glaucoma, the underlying cause must also be addressed. For example, if the glaucoma is secondary to uveitis, the inflammation must be controlled to prevent further damage to the drainage angle. ## Trauma in Depth: Mechanisms and Management Trauma is a common cause of a red eye in cats, particularly in those that spend time outdoors or live in multi-cat households. The type and severity of the injury determine the clinical signs and the treatment plan. Cat fights are a leading cause of ocular trauma. Bite wounds and scratches can injure the eyelids, the cornea, the sclera, and the internal structures of the eye. A scratch to the cornea can create a corneal ulcer, which is painful and can become infected. A bite wound to the eyelid can cause swelling, bruising, and a visible laceration. In some cases, the injury can penetrate the globe, causing a rupture. A ruptured globe is a surgical emergency that requires immediate attention to save the eye. Blunt force trauma, such as being hit by a car or struck by a blunt object, can cause internal bleeding within the eye. Hyphema, or blood in the anterior chamber, is a common finding after blunt trauma. The blood can obscure the view of the internal structures and can increase intraocular pressure if it blocks the drainage angle. Blunt trauma can also cause retinal detachment, lens luxation, or damage to the optic nerve. Foreign bodies can become lodged under the eyelid or penetrate the cornea. Grass seeds, plant material, and small objects are common culprits. A foreign body under the eyelid can cause persistent irritation, redness, and tearing. A penetrating foreign body can cause a corneal laceration and introduce bacteria into the eye, leading to endophthalmitis, a severe infection of the internal structures of the eye. Chemical irritation can occur if a cat comes into contact with household cleaners, solvents, or other irritants. Chemical burns to the cornea can cause severe pain, redness, and corneal clouding. The treatment for chemical exposure is immediate and copious flushing with sterile saline or water, followed by veterinary evaluation. The diagnostic approach to trauma begins with a thorough ophthalmic examination. The veterinarian will assess the eyelids, the cornea, the anterior chamber, the lens, and the retina. A fluorescein stain test is essential to identify corneal ulcers or lacerations. Tonometry is performed to measure intraocular pressure, which can be low if the globe has ruptured or high if the drainage angle is blocked. Imaging, such as radiography or ultrasound, may be recommended if there is suspicion of a foreign body or a fracture of the bony orbit. The treatment of trauma depends on the specific injury. Corneal ulcers are treated with topical antibiotics and pain relief. Deep ulcers or lacerations may require surgical repair. Hyphema is treated with rest and anti-inflammatory medications, and the cat may need to be confined to a quiet, dark space to reduce activity. Foreign bodies are removed surgically if necessary. A prolapsed eye, in which the eyeball is displaced from the socket, requires immediate surgical replacement and may have a guarded prognosis for vision. ## Owner Observation and Preparation for the Veterinary Visit Your observations at home are valuable to the veterinarian. Before you bring your cat in, take note of the following details, as they will help guide the diagnostic process. First, note when you first noticed the redness. Was it sudden or gradual? Did it appear after a known event, such as a fight with another cat, exposure to a chemical, or a fall? Sudden onset of redness after trauma is more suggestive of injury, while gradual onset over days or weeks is more consistent with uveitis or glaucoma. Second, observe whether the redness is in one eye or both. Unilateral redness is more likely to be caused by trauma or a localized problem. Bilateral redness raises the suspicion of a systemic disease. Third, note any other signs your cat is showing. Is your cat squinting, tearing, or pawing at the eye? Is the eye cloudy or dull? Is the pupil small or large? Is your cat eating, drinking, and behaving normally? Any signs of systemic illness, such as lethargy, fever, or loss of appetite, are important to report. Fourth, consider your cat's environment and lifestyle. Does your cat go outdoors? Is there a history of exposure to other cats? Are there any plants, chemicals, or small objects in the home that could have caused an injury? This information can help the veterinarian narrow down the list of possible causes. When you call the veterinary clinic, be prepared to describe the signs you have observed and to answer questions about your cat's vaccination status, parasite prevention, and any medications your cat is currently taking. If your cat is on any long-term medications, such as those for chronic kidney disease or hyperthyroidism, be sure to mention this, as it can affect the diagnostic and treatment plan. During the examination, the veterinarian will likely ask you to restrain your cat gently while they perform the ophthalmic tests. It is helpful to bring your cat in a carrier to reduce stress and to prevent escape. If your cat is painful, the veterinarian may recommend sedation or anesthesia to allow a thorough examination without causing additional distress. ## The Role of Systemic Disease in Feline Eye Disease The eye is often described as a window to the body, and in cats, this is particularly true. Many systemic diseases can cause ocular signs, and the eye may be the first place that a problem becomes apparent. Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses that suppress the immune system and predispose cats to a variety of infections and cancers. Both viruses can cause uveitis, either directly or through secondary infections. FeLV is also associated with lymphoma, which can affect the eye. Testing for these viruses is an important part of the uveitis workup, especially in cats that go outdoors or have a history of fighting. Feline infectious peritonitis (FIP) is a fatal coronavirus infection that causes widespread inflammation, including uveitis. The ocular signs of FIP can include uveitis, chorioretinitis, and changes in the appearance of the retina. FIP is more common in young cats and in cats from multi-cat environments. The diagnosis of FIP is challenging and often requires a combination of blood tests, imaging, and analysis of fluid from the abdomen or chest. Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii. Cats are the definitive host, and they become infected by hunting and eating infected prey. The parasite can cause uveitis, and it can also affect the central nervous system, causing neurological signs. Testing for toxoplasmosis involves measuring antibody levels in the blood, but the interpretation of these tests can be complicated because many cats have been exposed to the parasite without developing clinical disease. Fungal infections, such as histoplasmosis, blastomycosis, and cryptococcosis, can cause uveitis and other ocular signs. These infections are more common in certain geographic regions, and they are acquired by inhaling fungal spores from the environment. The diagnosis is made by identifying the organism in tissue samples or by serologic testing. Systemic hypertension is a common problem in older cats, and it is often associated with chronic kidney disease or hyperthyroidism. High blood pressure can cause bleeding within the eye, leading to hyphema and uveitis. It can also cause retinal detachment, which results in sudden blindness. Measuring blood pressure is a routine part of the ophthalmic examination in cats, especially those over seven years of age. ## Special Population Considerations The approach to a red eye can vary depending on the cat's age, breed, and health status. Kittens are more susceptible to infectious diseases, and they may develop uveitis as a result of feline herpesvirus, calicivirus, or other infections. Kittens are also more likely to experience trauma from play or from interactions with other kittens. A red eye in a kitten should be evaluated promptly, as early treatment can prevent long-term complications. Senior cats are more likely to have systemic diseases such as hypertension, chronic kidney disease, hyperthyroidism, and cancer. These conditions can cause uveitis or secondary glaucoma. A red eye in a senior cat should prompt a thorough systemic workup, including blood pressure measurement, blood tests, and urinalysis. Cats with pre-existing health conditions, such as diabetes mellitus, chronic kidney disease, or hyperthyroidism, may be at higher risk for ocular complications. Diabetes can cause cataracts, which can lead to lens-induced uveitis. Chronic kidney disease is associated with hypertension, which can cause retinal detachment and hyphema. Hyperthyroidism can also cause hypertension and ocular signs. Breed is not a reliable predictor of eye disease in cats, but certain breeds may have a higher risk of specific conditions. For example, primary glaucoma is rare in cats but has been reported in some breeds, such as the Siamese and the Burmese. However, the most common causes of red eye in cats, including uveitis, secondary glaucoma, and trauma, are not breed-specific. Your veterinarian will base their diagnosis on clinical findings, not on breed alone. ## The Importance of Follow-Up Care Eye conditions in cats often require ongoing management, and follow-up visits are essential to monitor the response to treatment and to adjust the plan as needed. For cats with uveitis, the veterinarian will want to recheck the eye to ensure that the inflammation is resolving and that the intraocular pressure remains within the normal range. Repeated tonometry is important because uveitis can lead to secondary glaucoma, and early detection of elevated pressure allows for prompt intervention. For cats with glaucoma, follow-up visits are critical to monitor the intraocular pressure and to adjust medications. The pressure can fluctuate, and the response to treatment can change over time. If the pressure cannot be controlled with medication, surgical options may be discussed. For cats with trauma, follow-up visits are needed to ensure that corneal ulcers are healing, that lacerations are healing without infection, and that any internal injuries are resolving. The veterinarian may recommend a recheck examination within a few days to a week after the initial treatment. During follow-up visits, the veterinarian will also assess the cat's comfort and quality of life. If the eye is painful and vision cannot be saved, enucleation may be recommended. Many cats adapt well to life with one eye, and the removal of a painful eye can significantly improve their quality of life. ## Prognosis and Quality of Life Considerations The prognosis for a cat with a red eye depends on the underlying cause, the severity of the disease, and the speed with which treatment is initiated. For uveitis, the prognosis is variable. If the underlying cause is infectious and can be treated, the inflammation may resolve completely. However, chronic uveitis can lead to complications such as cataracts, synechiae, secondary glaucoma, and retinal detachment. These complications can cause permanent vision loss, even if the inflammation is controlled. The goal of treatment is to preserve vision and comfort for as long as possible. For glaucoma, the prognosis for vision is poor if the pressure is not controlled quickly. Once vision is lost, it is usually permanent. The goal of treatment is to maintain comfort and quality of life. In cases where the eye is blind and painful, enucleation may be the most humane option. For trauma, the prognosis varies widely depending on the severity of the injury. Minor corneal ulcers heal well with treatment. Severe injuries, such as a ruptured globe or a prolapsed eye, have a guarded to poor prognosis for saving the eye. In these cases, the priority is to relieve pain and prevent infection. Regardless of the diagnosis, your cat's comfort and quality of life are the primary considerations. Eye conditions are painful, and cats may hide their pain well. If you notice any signs of discomfort, such as squinting, pawing at the eye, or changes in behavior, contact your veterinarian. Early intervention can make a significant difference in the outcome. ## The Value of Preventive Care Prevention is always better than treatment, and there are steps you can take to reduce your cat's risk of developing a red eye. Keeping your cat indoors is the single most effective way to prevent trauma from fights, accidents, and exposure to infectious diseases. Indoor cats are less likely to be injured by other animals, hit by cars, or exposed to toxins. If your cat does go outdoors, consider supervised outdoor time in a secure enclosure or on a harness and leash. Vaccination is important to protect against infectious diseases that can cause uveitis. Feline panleukopenia, feline herpesvirus, and calicivirus are core vaccines that are recommended for all cats. Your veterinarian can recommend a vaccination schedule based on your cat's age, lifestyle, and risk factors. Regular veterinary checkups are essential for early detection of systemic diseases that can affect the eyes. Annual or semi-annual examinations can detect hypertension, kidney disease, hyperthyroidism, and other conditions before they cause ocular complications. Blood pressure measurement should be a routine part of the examination in senior cats. Parasite prevention is also important. Fleas, ticks, and [intestinal parasites](/knowledge/parasites/pet-parasites/intestinal-parasites-dogs-cats-identification-treatment) can transmit diseases that cause uveitis. Your veterinarian can recommend a parasite prevention program based on your cat's lifestyle and risk factors. Finally, be observant. Check your cat's eyes regularly for any signs of redness, cloudiness, discharge, or changes in pupil size. Early detection of a problem allows for prompt treatment and a better outcome. ## When to Seek Emergency Care Some eye conditions require immediate veterinary attention. Contact your veterinarian or an emergency veterinary clinic right away if your cat has any of the following signs: - A red eye that persists for more than a few hours. - Squinting, excessive blinking, or pawing at the eye. - A cloudy, blue, or hazy cornea. - A change in pupil size, either constricted or dilated. - Bleeding from the eye or visible wounds. - An obviously swollen or enlarged eyeball. - Signs of systemic illness, such as lethargy, loss of appetite, or fever. - Any sudden change in vision or bumping into objects. Do not wait to see if the signs resolve on their own. Eye conditions are painful and can lead to permanent blindness quickly. Prompt veterinary care is essential. ## The Limitations of Owner Observation While your observations are valuable, there are limits to what you can determine at home. You cannot measure intraocular pressure, you cannot perform a fluorescein stain test, and you cannot examine the internal structures of the eye. The redness you see may be caused by a surface condition, such as conjunctivitis, or by a deep intraocular disease, such as uveitis or glaucoma. The treatment for these conditions is very different, and using the wrong treatment can cause harm. For example, a cat with a corneal ulcer may appear to have a red, painful eye. If you were to administer a corticosteroid eye drop, the ulcer could worsen, leading to a perforation of the globe. A cat with glaucoma may appear to have a red, cloudy eye. If you were to administer a medication that increases intraocular pressure, the damage to the optic nerve could accelerate. This is why it is essential to seek veterinary care for any red eye in your cat. The veterinarian has the training, the equipment, and the experience to make an accurate diagnosis and to recommend the appropriate treatment. Do not attempt to diagnose or treat the problem yourself. ## The Role of the Veterinary Ophthalmologist In some cases, your general practice veterinarian may refer you to a veterinary ophthalmologist for specialized care. A veterinary ophthalmologist has advanced training in the diagnosis and treatment of eye diseases and has access to specialized equipment, such as slit-lamp biomicroscopy, indirect ophthalmoscopy, and electroretinography. A referral may be recommended if the diagnosis is unclear, if the condition is severe or complex, or if the response to treatment is poor. A veterinary ophthalmologist can provide a more detailed examination, perform advanced diagnostic tests, and offer surgical options that may not be available in general practice. If your cat is referred to a veterinary ophthalmologist, be prepared to provide a complete history, ## Frequently Asked Questions **1. Can I use human eye drops on my cat's bloodshot eyes?** No, never use human eye drops on your cat without veterinary instruction, as they can be toxic, ineffective, or worsen the condition, especially steroid drops. **2. Is a bloodshot eye in a cat always an emergency?** While not every case is life-threatening, any red eye should be considered urgent because it can indicate painful and vision-threatening conditions like glaucoma or uveitis that require prompt treatment. **3. What is the most common cause of a red eye in cats?** Uveitis, or inflammation inside the eye, is a very common cause of red eyes in cats and is often linked to an underlying infectious or systemic disease. **4. How can I tell if my cat's red eye is from glaucoma or uveitis?** You cannot tell the difference at home; glaucoma often involves a dilated pupil and a cloudy, painful eye, while uveitis often involves a constricted pupil, but only a veterinarian with a tonometer can accurately measure eye pressure. **5. Can a cat fight cause a bloodshot eye?** Yes, trauma from a cat fight is a common cause, and scratches or bites can lead to corneal ulcers, uveitis, or severe infections that require immediate veterinary care. **6. Will my cat go blind from a bloodshot eye?** The risk of blindness depends on the cause and how quickly treatment is started; glaucoma and severe uveitis can cause permanent vision loss if not treated promptly. **7. What should I do while waiting for the vet appointment?** Keep your cat in a quiet, dark room, prevent them from scratching or rubbing their eye, and do not administer any medication unless specifically directed by your veterinarian. **8. Why is my cat squinting with a red eye?** Squinting is a sign of pain and light sensitivity, which are common symptoms of uveitis, corneal ulcers, or glaucoma, and it indicates the need for prompt veterinary evaluation. ## Frequently Asked Questions (Structured Data) ## Related Clinical & Scientific Guides * [My Cat Does Not Cough Up Hairballs](/knowledge/veterinary-medicine/symptom-guides/my-cat-does-not-cough-up-hairballs) * [Why Is My Cat developing dandruff suddenly? Walking Dandruff Cheyletiella and Diet](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-developing-dandruff-suddenly-walking-dandruff-cheyletiella-and-diet) * [Cat Diarrhea Home Treatment](/knowledge/veterinary-medicine/symptom-guides/cat-diarrhea-home-treatment)