CONDITION
Pannus (Chronic Superficial Keratitis)
Pannus is a condition in which the immune system begins to treat part of the eye's surface as something foreign, leading to inflammation and the gradual appearance of a pigmented, fleshy tissue that can grow across the cornea. It tends to start at the outer edge of the eye and move inward over time, and both eyes are often affected, though not always at the same rate. Certain breeds, particularly German Shepherd Dogs and their relatives, develop this condition more often than others, and it is sometimes referred to as chronic superficial keratitis. Owners often notice a dark or reddish discolouration beginning at the corner of the eye, or a hazy, thickened appearance to the clear part of the eye. In some animals, there may be slight discharge or mild squinting, though many dogs show little obvious discomfort in the early stages. The changes can be subtle at first and may be mistaken for a simple irritation or ageing. This page explores what an owner may observe, what is happening beneath the surface, how the condition is investigated, and the range of approaches used to manage it over time.
Why this matters now
Pannus tends to appear in young to middle-aged dogs, often becoming noticeable between two and five years of age, though the timing can vary. German Shepherd Dogs, Belgian Shepherds, Border Collies, and Greyhounds develop the condition more frequently than other breeds, suggesting an inherited component to susceptibility. Environmental factors, particularly exposure to ultraviolet light and living at higher altitudes, appear to influence both the likelihood of developing pannus and the speed at which it progresses in affected animals.
The condition typically begins as subtle discolouration or haziness at the outer corner of one or both eyes, then extends slowly across the corneal surface over months to years. The rate of progression varies considerably between individuals; some dogs experience gradual change with long periods of stability, whilst others may see more rapid thickening and pigmentation if the underlying inflammation is not addressed. Left unmanaged, the tissue can eventually cover large portions of the cornea, reducing the amount of light that reaches the retina and affecting vision in the longer term.
Signals & patterns
Early signals
Pink or reddish film at eye corner
A faint pinkish or reddish tissue may appear at the outer edge of the eye, where the white meets the clear cornea. This represents inflammation and new blood vessel growth beginning to extend onto the corneal surface.
Slight haziness over the cornea
The normally transparent cornea may develop a faint cloudy or milky appearance, often most noticeable in bright light. This early change reflects fluid accumulation and cellular activity beneath the surface.
Dark pigment creeping inward
A brownish or greyish discolouration may begin at the edge of the cornea and gradually move toward the centre over time. This pigmentation develops as the body deposits melanin in response to chronic inflammation.
Minimal or absent discomfort
Many dogs in the early stages show little sign of pain or irritation, and may not squint or rub at the eye. The absence of obvious distress can make the condition easy to overlook during routine observation.
Later signals
Thickened, fleshy tissue over cornea
As the condition advances, the corneal surface may appear noticeably thickened, with a raised, fleshy texture where clear tissue once was. This represents ongoing immune activity and tissue remodelling that has accumulated over months or years.
Widespread pigmentation obscuring vision
In later stages, dense brown or black pigment can cover substantial portions of the cornea, reducing the clarity of the eye and potentially affecting the animal's ability to see clearly, particularly in affected areas.
Occasional mucoid discharge
Some dogs develop a sticky, mucus-like discharge at the corners of the eyes as the condition progresses, reflecting ongoing surface irritation and tear film disruption, though this is not present in all cases.
Click to read about the biological mechanisms
How this is usually investigated
Pannus is often suspected from the characteristic appearance and location of the corneal changes, combined with breed and age. A veterinary professional will typically begin with a careful history, noting when the changes were first observed, which eye was affected first, and whether the animal has spent significant time in bright sunlight or at altitude. The examination focuses on the eye's surface under magnification, and in most cases the clinical picture is distinctive enough that additional testing serves to rule out other conditions rather than confirm pannus itself.
Ophthalmic examination with magnification
Fluorescein staining
Schirmer tear test
Corneal cytology or biopsy
Options & trade-offs
Management of pannus typically involves reducing the immune-driven inflammation in the cornea and minimising factors that worsen the process, particularly ultraviolet light exposure. Most approaches do not cure the condition but aim to control it over the long term, slowing progression and preserving vision. The combination of treatments and the intensity with which they are used can be adjusted over time depending on how the individual animal responds and what the owner finds manageable in daily life.
Topical corticosteroids
Anti-inflammatory eye drops or ointments containing corticosteroids are applied directly to the eye's surface, often multiple times each day initially, with the frequency reduced once the inflammation is controlled. These medications suppress the local immune response, reducing redness, swelling, and the rate at which new pigmentation and blood vessels form. Many dogs require ongoing treatment, sometimes for life, with the dose and frequency adjusted according to how the cornea appears over time.
Trade-offs: Long-term use of corticosteroids in the eye can increase the risk of secondary infections, delay healing if the corneal surface is damaged, and in some cases raise intraocular pressure. The need for frequent application can be challenging for some owners, and the cost of medication accumulates over months and years.
Topical ciclosporin
Ciclosporin is an immunomodulating agent that can be applied as an eye drop or ointment, working to dampen the immune activity within the corneal tissue without the broader effects of corticosteroids. It is often used alone or in combination with corticosteroids, and in some animals it allows a reduction in the frequency or strength of steroid treatment once the condition is stable. The medication is typically applied twice daily, though the regimen can be adjusted depending on response.
Trade-offs: Ciclosporin can take several weeks to show its full effect, so it is less useful for rapid control of active inflammation. It tends to be more expensive than corticosteroid preparations, and some animals do not respond as well to it. The formulation can cause mild stinging or irritation in a small number of dogs.
Reducing ultraviolet light exposure
Because ultraviolet light appears to worsen the inflammatory process in pannus, limiting exposure can slow progression. This may involve keeping the dog indoors during the brightest part of the day, seeking shade during walks, or in some cases using protective eyewear designed for dogs. The degree to which this approach is practical depends on the animal's lifestyle, temperament, and the owner's environment.
Trade-offs: Reducing sun exposure does not reverse existing changes and is unlikely to control active inflammation on its own, but it can complement medical treatment and may reduce the amount of medication needed over time. Protective eyewear is not tolerated by all dogs, and significant lifestyle adjustments may not be feasible for every household.
Surgical debulking or keratectomy
In cases where pigmented tissue has become very thick and is significantly obstructing vision, surgical removal of the affected corneal layers can be considered. The procedure involves carefully shaving away the abnormal tissue under general anaesthesia, which can improve clarity temporarily. However, the underlying immune process remains, and the tissue often regrows unless medical management is continued afterward.
Trade-offs: Surgery carries the usual risks of anaesthesia and can cause discomfort during the healing period. The improvement in vision may be temporary if inflammation is not controlled medically, and repeat procedures may be needed. It tends to be considered when medical management alone has not preserved sufficient vision or when the owner wishes to address advanced changes that developed before treatment began.
Common misconceptions
"Pannus can be cured with a single course of treatment and will not return."
Pannus is a chronic condition driven by an ongoing immune response, and in most dogs it requires long-term management rather than a single curative intervention. Stopping treatment often leads to a recurrence of inflammation and progression of the tissue changes, so many animals remain on some form of medication for the rest of their lives, with adjustments made as needed.
"The pigmentation on the cornea will disappear completely once treatment begins."
Treatment aims to halt or slow the progression of new pigment and blood vessel formation, but existing pigmentation and tissue changes may not fully reverse. Some lightening can occur over time, particularly in the early stages, but advanced pigmentation tends to be permanent. The goal is typically to preserve the remaining clear cornea and maintain functional vision rather than to restore the eye to its original appearance.
"Only German Shepherd Dogs develop pannus, so other breeds are not at risk."
Whilst German Shepherd Dogs are disproportionately affected, pannus can occur in many breeds, including Belgian Shepherds, Border Collies, Greyhounds, and occasionally mixed-breed dogs. The condition is less common outside these groups, but any dog exposed to the right combination of genetic predisposition and environmental triggers can develop it. Breed is a useful indicator of risk but not an absolute boundary.
Related conditions
Keratoconjunctivitis Sicca (Dry Eye)
Keratoconjunctivitis sicca can co-exist with pannus, particularly in German Shepherd Dogs and related breeds, and both conditions involve immune-mediated processes affecting the eye's surface. Reduced tear production may worsen the irritation and pigmentation seen in pannus, and managing both conditions together often requires careful coordination of treatment.
Eosinophilic Keratitis in Cats
Eosinophilic keratitis in cats shares a similar pattern of immune-mediated inflammation on the corneal surface, though the cell types and species affected differ. Both conditions produce visible changes to the cornea—often with pigmentation or tissue proliferation—that can progress if left unmanaged.
Discoid Lupus Erythematosus
Discoid lupus erythematosus is another immune-mediated condition that can affect German Shepherd Dogs and related breeds, and in some cases both conditions may be present in the same animal. The shared tendency toward immune dysregulation in certain breed lines means that owners observing skin changes on the nose or face may also be managing concurrent ocular disease.
Canine Parvovirus
Corneal ulcers can develop secondarily in eyes affected by pannus, particularly when the corneal surface becomes thickened, dry, or compromised by chronic inflammation. The proliferative tissue and pigmentation associated with pannus may alter the cornea's protective barrier, making it more vulnerable to superficial injury.
Uveitis
Uveitis describes inflammation deeper within the eye and may occasionally occur alongside pannus, particularly in breeds predisposed to immune-mediated eye disease. While pannus primarily affects the corneal surface, the presence of concurrent intraocular inflammation can complicate diagnosis and may influence the broader approach to management.
Pannus sits within a broader group of immune-mediated conditions that can affect various parts of the body, and understanding how the immune system behaves in one area can sometimes inform observations elsewhere. Some owners find it helpful to explore related content on immune and inflammatory health, particularly if their dog has shown signs of sensitivity or reactivity in other systems. For those managing the condition over time, periodic discussions about how the eyes are responding, what the current treatment routine involves, and whether any adjustments might be considered can form a useful part of ongoing care.