Posterior Uveitis in Cats: Symptoms, Causes, Diagnosis & Treatment

What Is Posterior Uveitis in Cats?

Posterior uveitis in cats is a serious, often subtle eye disease that hides at the back of the eye and can quietly steal vision if left untreated. Unlike anterior uveitis (inflammation at the front of the eye), this form develops in the deep, vascular layer of the eye and is frequently mistaken for a minor problem until significant damage has already occurred.

Anatomically, posterior uveitis refers to inflammation of the choroid, the blood-vessel-rich layer sandwiched between the retina and the white of the eye (the sclera) ^{[1, 2]}. Because the choroid and the retina lie so closely together and share a blood supply, choroidal inflammation almost always spreads into the retina, producing what veterinarians call chorioretinitis ^{[3, 4]}. In clinical practice, the terms posterior uveitis and chorioretinitis are used interchangeably.

Posterior uveitis can occur on its own or alongside anterior uveitis (iridocyclitis). When both the front and back of the uvea are inflamed, the condition is called panuveitis; if the inflammation extends to involve all internal eye structures, including the vitreous (the gel that fills the eyeball), it is called endophthalmitis ^[5]. The clinical signs of posterior uveitis are often less dramatic than those of anterior uveitis, but the disease is still painful and threatens vision ^{[3, 4]}.

Perhaps most importantly, posterior uveitis in cats is rarely a "stand-alone" eye problem. It is frequently a warning sign of a broader systemic illness, ranging from viral infections to cancer, so finding this disease should always trigger a search for an underlying cause ^[3].

Signs and Symptoms to Watch For

Because posterior uveitis develops behind the lens, the visible clues are often faint, but careful owners and veterinarians can catch them early. Cats are masters at hiding discomfort, and the disease is frequently diagnosed only after permanent damage has already begun ^[4].

External signs of ocular discomfort such as squinting (blepharospasm), light sensitivity (photophobia), and redness of the white of the eye or inner eyelid (conjunctival hyperemia) may be present but are usually subtle. Many cats instead show vague behavioral changes, hiding, reduced interaction, lethargy, or a poor appetite, that owners may not initially connect to the eyes ^{[5, 4, 6]}. A thorough fundic examination (a look at the back of the eye with specialized instruments) after pupil dilation is the key to diagnosis. Common findings include ^{[7, 1]}:

• Dark or dull patches in the reflective "tapetum" (the mirror-like layer behind the retina), called hyporeflective lesions
• Gray-white infiltrates in the non-tapetal (usually pink or pigmented) fundus
• Retinal hemorrhages
• Exudative retinal detachments (blisters of fluid lifting the retina off the back of the eye)
• Vitreous haze or debris from inflammatory cells
• Perivascular cuffing (white sheathing around retinal blood vessels)

Fungal infections and FIP-related inflammation often produce chorioretinal granulomas, raised, pale, frequently perivascular nodules that are a classic finding on fundoscopy ^[4]. Acute disease features retinal edema and detachment, whereas chronic disease shows a thinned retina, tapetal hyperreflectivity (a brighter reflective area where retina has been lost), pigment clumping, and visibly narrowed (attenuated) retinal blood vessels ^{[2, 8]}.

If the optic nerve is also inflamed (optic neuritis), cats may suddenly lose vision, and the optic nerve head may appear swollen, red, and elevated on examination ^[1]. Cats with infectious causes frequently also have fever, lethargy, loss of appetite, or enlarged lymph nodes, all of which guide the diagnostic work-up ^{[5, 2]}.

Causes and Risk Factors

Infectious agents are the most commonly identified cause of posterior uveitis in cats, but the disease can also be immune-mediated, neoplastic, traumatic, or metabolic. The biggest infectious players are feline infectious peritonitis virus (FIP), feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), and the parasite Toxoplasma gondii ^{[5, 4, 3]}.

Systemic fungal infections such as Cryptococcus, Histoplasma, and Blastomyces have a strong predilection for the back of the eye and typically cause granulomatous chorioretinitis ^{[4, 3]}. Bartonella henselae (the cat-scratch bacterium) is frequently discussed as a cause, but its true role remains controversial because many healthy cats carry antibodies to it ^{[5, 2, 4]}. Immune-mediated (non-infectious) posterior uveitis is characterized by lymphoplasmacytic infiltration (an excess of white blood cells called lymphocytes and plasma cells) on tissue samples; many idiopathic cases are believed to be autoimmune in nature ^{[2, 1, 8]}.

Cancer, particularly lymphoma, can infiltrate the uvea and retina, producing uveitis with retinal detachment and subretinal masses. Melanoma, by contrast, rarely incites significant inflammation ^{[8, 1, 4]}. Penetrating ocular trauma can introduce bacteria or fungi and trigger endophthalmitis, though most traumatic uveitis is anterior ^{[4, 2]}. Systemic hypertension causes hypertensive choroidopathy and retinopathy that is grouped with the metabolic causes of uveitis, with edema, hemorrhage, and retinal detachment as classic findings ^[8].

Risk factors that increase a cat's chance of developing posterior uveitis (or its underlying triggers) include an outdoor lifestyle, lack of vaccination, male sex, middle age, and a domestic (mixed-breed) background ^{[5, 9]}. Despite a thorough work-up, the underlying cause remains unidentified in 30–70% of feline uveitis cases, a striking gap that highlights the need for continued research ^{[5, 8, 4]}.

Types of Posterior Uveitis in Cats

Posterior uveitis is classified by anatomical location, duration, and underlying cause, and each classification guides how veterinarians investigate and treat the disease.

By anatomical location, the main forms are:

• Choroiditis, inflammation limited to the choroid (rarely confirmed in practice) ^{[1, 5]}
• Chorioretinitis, inflammation involving both the choroid and retina, by far the most common form ^[4]
• Retinitis, primary retinal inflammation, often viral in origin ^{[5, 10]}
• Optic neuritis, inflammation focused on the optic nerve head ^[1]

Because the choroid and retina are so intimately connected, pure choroiditis or retinitis is rarely confirmed clinically; chorioretinitis is the everyday term ^{[3, 4]}. When anterior uveitis coexists, the condition is panuveitis, meaning the entire uveal tract is inflamed, common with FIP and the systemic mycoses ^{[5, 4]}.

By duration, posterior uveitis is acute when signs develop over days with active edema, detachment, and hemorrhage; it is chronic when lasting weeks to months with degenerative changes, scarring, and ultimately a shrunken, non-functional eye (phthisis bulbi) ^{[2, 8]}.

By cause, it is classified as infectious (viral, bacterial, fungal, protozoal, parasitic), non-infectious or immune-mediated (presumed autoimmune or lens-induced), neoplastic (lymphoma), traumatic, or metabolic (hypertension), each with distinct clinical and prognostic implications ^{[5, 8, 1]}.

How Vets Diagnose Posterior Uveitis

Diagnosis begins with a careful history and a complete physical examination because most cats have clues elsewhere in the body that point to a systemic cause. Vision loss in cats may be hard for owners to detect unless both eyes are affected, so vets rely heavily on a structured work-up rather than owner observations alone ^{[9, 4, 2]}.

The diagnostic pathway typically includes:

• Pupil dilation with tropicamide eye drops, mandatory to evaluate the back of the eye. Without dilation, fundic lesions are easily missed ^[2].
• Indirect ophthalmoscopy using a 20D or 28D handheld lens, the screening method of choice, providing a wide-field view of chorioretinal lesions, vitreal cells, and retinal detachment ^[2].
• Baseline laboratory tests, complete blood count, serum biochemistry, and urinalysis screen for systemic disease, though results are often normal in idiopathic uveitis ^{[2, 4]}.
• Targeted infectious-disease testing guided by risk factors and geography: FeLV/FIV serology, FIP antibody or PCR (a DNA-based test that detects the virus), Toxoplasma IgG/IgM, cryptococcal antigen, and Bartonella serology ^{[5, 4]}.
• Imaging, thoracic and abdominal radiographs or ultrasound help identify hidden cancer or fungal spread ^{[5, 4]}.
• Ocular ultrasonography, invaluable when blood or cataract blocks the view of the back of the eye, revealing retinal detachment, masses, or vitreal debris ^[5].

Typical ophthalmoscopic findings include vitreous debris, retinal hemorrhages, hyporeflective patches, granulomas, and retinal detachment, acute lesions look edematous and swollen, chronic ones look scarred and hyperreflective ^{[4, 7, 1, 2]}. Bilateral involvement strongly suggests a systemic cause such as FIP or fungal disease, while unilateral disease may be exogenous (from outside the body) or idiopathic ^[4].

Aqueocentesis (sampling of the fluid inside the front chamber of the eye) is rarely performed because it requires general anesthesia, carries a risk of worsening uveitis, and has a low diagnostic yield, it is reserved for refractory cases or when an intraocular infection is strongly suspected ^[5]. Serology results must always be interpreted cautiously: a positive titer indicates exposure, not necessarily current disease, and persistent IgG antibodies to Toxoplasma are common in healthy cats ^[4]. Referral to a veterinary ophthalmologist is recommended for complex cases, diagnostic uncertainty, or when advanced imaging or surgery is considered ^[5].

Treatment Options for Posterior Uveitis

Systemic therapy is the cornerstone of treatment because topical eye drops cannot reach therapeutic levels at the back of the eye. Treatment is tailored to both the inflammation itself and the underlying cause ^{[4, 1]}.

Nonspecific anti-inflammatory treatment aims to control inflammation and pain while diagnostic tests are pending. Systemic corticosteroids such as oral prednisolone, given at anti-inflammatory doses and gradually tapered, are first-line, provided infectious causes have been reasonably excluded ^{[4, 2]}. Non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam are an alternative for cats that cannot tolerate steroids, but they carry a risk of gastrointestinal ulceration and should be used cautiously, especially in debilitated cats ^{[5, 7]}.

Specific treatments depend on the cause:

• Toxoplasmosis, clindamycin (an antibiotic) is the treatment of choice, combined with anti-inflammatory therapy ^[2]
• Bartonella-associated uveitis, prolonged courses of doxycycline or azithromycin are often used, although the definitive benefit of antimicrobials remains debated ^[2]
• Systemic fungal chorioretinitis, itraconazole or fluconazole, with treatment often prolonged and the prognosis for vision guarded ^{[3, 4]}
• Idiopathic or immune-mediated uveitis, may require additional immunosuppressive agents such as azathioprine or cyclosporine if corticosteroids alone are insufficient, after rigorous exclusion of infection ^[5]
• FIP uveitis, historically managed palliatively with prednisolone; today, specific antiviral therapy (see next section) offers a curative option ^[7]
• Lymphoma, systemic chemotherapy often produces a dramatic reduction in ocular inflammation, with topical corticosteroids as adjunctive therapy; radiation is not a realistic option ^{[8, 4]}

Surgical intervention is rarely needed, but enucleation (surgical removal of the eye) is a valid option for blind, painful eyes that do not respond to medical therapy, providing permanent relief ^{[9, 7]}. Careful, gradual tapering of anti-inflammatory drugs based on clinical response is essential to prevent relapses and minimize side effects ^{[2, 4]}.

New and Emerging Treatments

The single biggest recent advance in feline posterior uveitis is the advent of antiviral therapy for FIP, which has converted what was once a fatal disease into a treatable one. Antiviral nucleoside analogues, most notably remdesivir and GS-441524, have transformed the prognosis for cats with FIP-associated uveitis ^[7].

In recent case series, 82% of cats with FIP uveitis achieved full clinical resolution, with chorioretinal lesions improving after a median of about 44 days of treatment ^[7]. Antiviral monotherapy (without concurrent corticosteroids) has shown promise, suggesting that specific viral suppression alone can resolve intraocular inflammation in FIP ^[7]. Retinal detachment secondary to FIP can even reattach and vision can be restored after antiviral and anti-inflammatory therapy, offering hope where blindness was previously inevitable ^[7].

Standard treatment regimens involve an 84-day course, often with high initial doses of injectable remdesivir followed by oral GS-441524, with monitoring for recurrence after completion ^[7]. Despite these encouraging results, long-term follow-up data are still limited; some cats develop persistent secondary glaucoma even after uveitis resolves and require ongoing management ^[7]. Research is ongoing to optimize dosing protocols, explore the efficacy of oral GS-441524, and evaluate whether treatment courses can be safely shortened ^[7]. Intravitreal drug delivery systems and novel immunomodulators are in early investigation but published evidence is currently lacking.

Complications and Long-Term Risks

Secondary glaucoma is the most serious complication of posterior uveitis and can lead to irreversible vision loss. It develops in up to 50% of cats with chronic uveitis and is one of the most common reasons for eventual enucleation ^{[6, 4, 8, 7, 11]}.

Other important complications include:

• Retinal detachment, may be serous (clear fluid) or exudative (inflammatory); early treatment can allow reattachment, but prolonged detachment causes retinal degeneration and permanent blindness ^{[3, 6, 7]}
• Cataracts and lens luxation, common sequelae of chronic uveal inflammation that further predispose to glaucoma ^{[6, 4]}
• Posterior synechiae and iris bombé, adhesions between the iris and lens, sometimes causing the iris to bulge forward and obstruct aqueous outflow, rapidly elevating eye pressure ^{[6, 11]}
• Phthisis bulbi, a shrunken, non-functional globe, the end-stage outcome of uncontrolled long-standing uveitis ^[8]
• Optic atrophy, a possible sequel to optic neuritis, visible as a pale, flattened optic disc on fundic exam, that can result in irreversible blindness

What this means for your cat: Even after uveitis appears to resolve, regular intraocular pressure monitoring is essential because glaucoma can emerge months to years later ^[7]. In up to 29% of affected feline eyes, the severity of complications eventually necessitates enucleation; however, most cats adapt well to seeing with only one eye ^{[4, 7]}.

Prognosis and What to Expect Long-Term

Prognosis depends heavily on the underlying cause, the chronicity of disease at diagnosis, and whether complications like glaucoma have developed. Toxoplasmosis and fungal uveitis often respond well to targeted therapy, while neoplastic uveitis carries a more guarded outlook ^{[3, 2]}. Idiopathic and immune-mediated posterior uveitis is typically chronic and relapsing, demanding ongoing vigilance and medication adjustments to prevent permanent damage ^{[5, 8]}.

Early detection and prompt treatment dramatically improve the likelihood of preserving vision; delayed presentation with chronic retinal degeneration frequently results in permanent blindness ^[4]. Cats with FIP uveitis historically had a grave prognosis; with antiviral therapy, the outlook has improved significantly, with many regaining vision and achieving remission ^[7].

The development of secondary glaucoma worsens the prognosis for ocular comfort and vision, often requiring long-term topical medication or enucleation ^[7]. If the underlying systemic disease (e.g., FIP or lymphoma) is fatal, that determines overall survival, ocular recovery alone does not guarantee a long life ^{[3, 7]}. With appropriate management, however, many cats retain functional vision and a good quality of life, and even those requiring enucleation can lead normal, pain-free lives once the source of pain is removed ^[7].

Living With and Managing Posterior Uveitis

Managing a cat with posterior uveitis is a long-term commitment that combines careful observation, faithful medication administration, and regular veterinary rechecks. Owners are the first line of defense against relapse.

You should monitor your cat for subtle signs of recurrence, including increased squinting, redness, cloudiness, or behavioral changes such as hiding or reduced appetite ^{[4, 6]}. Recheck intervals are initially frequent, often every 1–2 weeks, for intraocular pressure checks and fundic exams, then spaced out as the eye stabilizes. A typical tapering protocol doubles the interval if improvement is noted ^{[2, 4]}.

Anti-inflammatory medications must never be stopped abruptly. Reliance on slow, veterinarian-guided tapering reduces the risk of rebound inflammation ^{[2, 4]}. Cats with posterior uveitis associated with systemic disease may require referral to a veterinary ophthalmologist, frequent monitoring, additional treatments, or dietary adjustments, and ongoing communication between the ophthalmologist and primary veterinarian is essential ^[5]. For cats with permanent vision loss, environmental modifications such as avoiding stairs and minimizing furniture rearrangements can help them navigate safely. Enucleation, if required, eliminates pain and can markedly improve quality of life, cats adapt rapidly to monocular vision ^[7]. Long-term topical medications for uveitis are associated with complications in less than 5% of cats, but potential ocular complications such as corneal ulceration and conjunctivitis should still be monitored ^[12].

Prevention and Reducing Risk

Because posterior uveitis is so often tied to infectious or traumatic triggers, prevention focuses on limiting exposure and staying current on preventive care.

Practical steps to reduce your cat's risk include:

• Keeping cats strictly indoors to eliminate exposure to fight wounds, infectious vectors, and free-roaming hazards ^[9]
• Vaccinating against FeLV and keeping core vaccines current to lower the incidence of systemic infections that can trigger uveitis (no vaccine reliably prevents FIP or toxoplasmosis) ^[9]
• Using consistent flea and tick prophylaxis to reduce the risk of Bartonella-associated posterior uveitis, as fleas are the principal vector for Bartonella henselae ^[2]
• Scheduling routine wellness examinations, including blood pressure measurement and retroviral testing, to detect hypertension or infectious disease early ^{[8, 9]}
• Spaying or neutering to reduce roaming and fighting, indirectly decreasing the risk of fight-related eye injuries and infectious exposure ^[9]
• Feeding only cooked commercial diets and preventing hunting to reduce the risk of Toxoplasma gondii infection, since raw meat and prey can harbor tissue cysts

What We Still Don't Know: Gaps and Current Research

Despite major advances, especially the FIP antivirals, large knowledge gaps remain in feline posterior uveitis. A substantial proportion of cases (30–70%) remain idiopathic despite comprehensive work-up; the true identity and triggers of these immune-mediated cases are poorly understood ^{[8, 4]}.

The etiopathogenic role of Bartonella henselae remains controversial: many healthy cats are seropositive, and a causal link to uveitis is not firmly established ^{[5, 2, 4]}. Large-scale prospective clinical trials are lacking, so most treatment recommendations for idiopathic uveitis are based on anecdotal experience and small case series ^{[8, 4]}. Oral immune-modulating agents such as azathioprine and cyclosporine may be considered for idiopathic or lymphoplasmacytic uveitis when infectious and neoplastic causes have been ruled out ^[5].

The long-term ocular sequelae of FIP uveitis successfully treated with antivirals are not fully known; the incidence of late-developing glaucoma or retinal degeneration needs further follow-up ^[7]. Advanced imaging techniques such as optical coherence tomography (OCT) are not widely available in veterinary ophthalmology, limiting the ability to distinguish subtle inflammatory retinal changes from degenerative ones. Existing studies also consistently find an overrepresentation of male cats and domestic breeds among affected animals ^[8].

❓ Frequently Asked Questions