What is Dr. Zubair Khalid's research focus?

Dr. Zubair Khalid specializes in molecular virology, mRNA vaccine development, and computational biology, with a focus on avian pathogens like IBDV and Avian Reovirus.

Where is Dr. Zubair Khalid currently working?

Dr. Zubair Khalid is a Postdoctoral Research Associate at the University of Maryland (UMD), specifically within the Department of Animal and Avian Sciences.

Pannus in Dogs: Causes, Signs, and Treatment

Name: Pannus in Dogs: Causes, Signs, and Treatment
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-09-20

Pannus in dogs is an immune-mediated inflammation of the cornea, the clear front window of the eye, that causes dark pigment and blood vessels to grow across the surface and can lead to blindness if it is not controlled. The medical name is chronic superficial keratitis (CSK), and it is most common in German Shepherd Dogs, Border Collies, and Greyhounds, with ultraviolet light and high altitude acting as major triggers.

This article explains what pannus does to the eye, which dogs are at risk, how veterinarians diagnose it, and why treatment is a lifelong commitment rather than a short course of drops.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

What Pannus Actually Is

The cornea is normally clear and has no blood vessels. It stays that way because the body actively suppresses blood vessel growth and immune activity in that tissue. In pannus, that suppression fails. The immune system begins treating part of the cornea as foreign tissue and sends inflammatory cells into the superficial (outer) layers of the cornea.

Two things then happen at the same time. New blood vessels grow into the cornea from the limbus, the border where the clear cornea meets the white of the eye. At the same time, pigment (melanin) deposits in the superficial corneal stroma. The result is a cornea that gradually turns pink, then brown, then opaque. Because the cornea sits over the pupil and iris, this opacification blocks light and reduces vision.

The disease is described as superficial because the inflammation stays in the outer layers of the cornea rather than penetrating to the deep stroma or endothelium. It is described as chronic because it does not resolve on its own and recurs whenever treatment stops.

The Immune Mechanism

Pannus is an autoimmune condition. The strongest evidence comes from genetic studies. A specific major histocompatibility complex (MHC) class II haplotype, DLA-DRB1*01501/DQA1*00601/DQB1*00301, is significantly associated with CSK in German Shepherd Dogs, and dogs that are homozygous for this risk haplotype carry more than eight times the risk compared with dogs that are not [1]. Overall homozygosity of MHC class II genes also raises risk, which fits the pattern seen in other autoimmune diseases [1].

A separate study of the upstream regulatory regions of the same DLA genes found that a variant in DQB1 and a specific haplotype increased CSK risk roughly threefold, and dogs homozygous at DRB1 were at over four times the risk of heterozygotes [2]. These findings support the idea that CSK is inherited as an immune-mediated disease with a genetic component rather than being caused by infection or injury.

What happens inside the cornea matches this picture. In normal dog corneas, MHC class II expressing cells (mostly Langerhans cells) are found at the limbus and conjunctiva but very little in the central cornea [3]. In corneas with CSK, MHC class II expression appears on stromal cells, many of which are lymphocytes, and the corneal epithelial cells themselves start expressing MHC class II abnormally [3]. That is a sign of the immune system being actively engaged in the cornea.

The infiltrating cells are predominantly CD4 positive T lymphocytes, with fewer CD8 positive cells, and the CD4 to CD8 ratio rises above 4 at the advancing edge of the lesion [4]. Some of these lymphocytes contain gamma interferon, a cytokine that drives inflammation and helps explain the ongoing immune activation [4]. This is a T cell driven process, which is why treatments that suppress T cell activation (cyclosporine, tacrolimus) work.

UV Light and Altitude

Genetic risk alone does not explain why some dogs develop pannus and others do not. Ultraviolet (UV) light is the other major factor. The disease is more common in dogs living at high altitude, where UV exposure is greater, and it tends to worsen in summer. This is why pannus is sometimes called "German Shepherd pannus" or "altitude pannus" in older literature.

The UV connection has been tested directly. In a study of 26 dogs with CSK, UV-blocking soft contact lenses were placed in one eye of each dog while the other eye served as a control, and all dogs also received topical cyclosporine [5]. The lenses reduced UV radiation to a safe level when new, though used lenses lost that ability over time. The study found that pigmentation increased in both lens-wearing and control eyes over six months, and corneal edema increased in lens-wearing eyes [5]. The authors could not confirm a significant difference in pannus or vascularization between the two eyes, and adverse effects including corneal edema, vascularization, conjunctivitis, and blepharospasm occurred in six cases [5]. The takeaway is that UV blocking is biologically plausible and worth discussing with a veterinary ophthalmologist, but contact lenses are not a proven stand-alone therapy and carry their own risks.

For owners, the practical implication is straightforward. Reducing UV exposure, especially during peak daylight hours and at high altitude, is a reasonable supportive step. It does not replace medical treatment.

Which Dogs Get Pannus

Pannus is diagnosed most often in German Shepherd Dogs, but it occurs in other breeds, including Border Collies, Greyhounds, Australian Shepherds, Belgian Tervuren, and mixed breeds with those ancestries. The breed pattern is strong enough that genetics research has focused on specific populations.

In German Shepherd Dogs, a retrospective study of 308 affected dogs in Poland and Slovakia found the highest incidence between 5 and 8 years of age, with males affected more often than females (about 61 to 66 percent of cases depending on country) [6]. Depigmentation and thickening of the third eyelid margin occurred alongside CSK in roughly 63 to 69 percent of dogs, and the inflammatory process typically involved 2 to 3 quadrants of the cornea by the time of diagnosis [6]. That last point matters: many dogs are already in an advanced stage when the disease is first recognized.

An earlier genetic study in German Shepherd Dogs also noted a female predisposition in its study population, which differs from the male predominance in the retrospective survey [1]. The discrepancy suggests that sex predisposition is not fully settled and may vary by population.

In Greyhounds, the picture is different. A genome-wide association study of 109 Australian racing Greyhounds, 70 with CSK and the rest unaffected over four years of age, identified three co-located variants on chromosome 18 near the Epidermal Growth Factor Receptor (EGFR) gene [7]. The associated haplotype was protective for CSK, and EGFR is known to play a role in corneal healing by signaling epithelial cell proliferation and stromal keratocyte apoptosis [7]. This is a different genetic mechanism from the MHC association in German Shepherds, which suggests that pannus in different breeds may not be the same disease at the molecular level. A separate inheritance study in Australian Greyhounds also supports a genetic basis [8].

Table: Breed Risk and Typical Age of Onset

Breed	Relative Risk	Typical Age of Onset	Key Genetic Finding
German Shepherd Dog	Highest	5 to 8 years (peak incidence)	MHC class II risk haplotype DLA-DRB101501/DQA100601/DQB1*00301, OR 2.67 [1]
Greyhound (Australian racing)	High	Often detected after 4 years	Variants near EGFR on CFA18, protective haplotype [7]
Border Collie	Elevated (clinical recognition)	Variable, often young to middle-aged	No specific locus reported in these sources
Belgian Tervuren, Australian Shepherd	Elevated (clinical recognition)	Variable	No specific locus reported in these sources
Brachycephalic breeds (Pug, Pekingese, Shih Tzu, Boston Terrier)	Different disease (pigmentary keratitis)	Variable	Not immune-mediated in the same way

The table separates true pannus from pigmentary keratitis in flat-faced breeds, which is a different condition discussed below.

Signs of Pannus in Dogs

Early pannus can be easy to miss because it often starts at the outer edge of the cornea and does not cause obvious pain. Owners frequently notice something before the dog shows discomfort.

Common signs include:

A pink or fleshy appearance at the edge of the cornea, especially on the side facing the ear (temporal) or the side facing the nose (nasal)
Brown or black pigment spreading across the cornea
Redness of the conjunctiva (the membrane lining the eyelids and covering the white of the eye)
A hazy or cloudy look to the eye
Squinting, tearing, or sensitivity to light in some dogs
Thickening or depigmentation of the third eyelid margin
Reduced vision, especially in low light or at a distance

The pigment and blood vessels typically begin at the limbus and spread toward the center of the cornea. In advanced cases, the entire cornea can become opaque. The disease is usually bilateral, meaning both eyes are affected, but the two eyes are often not equally affected at the same time [6].

Some dogs develop a raised, fleshy nodule on the cornea. A case report described a German Shepherd Dog with a prior CSK diagnosis that developed a nonpainful, unilateral corneal nodule about 0.5 cm in diameter in the ventral paracentral cornea [9]. The nodule did not respond to topical dexamethasone, so a superficial keratectomy was performed, and histology showed a mass of plasma cells, B lymphocytes, T lymphocytes, and macrophages in the superficial corneal stroma [9]. This is a rare presentation, but it shows that pannus can produce nodular lesions that mimic other corneal diseases and may require surgical biopsy.

What Pannus Is Not

Pannus is sometimes confused with pigmentary keratitis, which is common in brachycephalic breeds such as Pugs, Pekingese, Shih Tzus, and Boston Terriers. The two conditions look similar because both involve brown pigment on the cornea, but the underlying cause is different.

Pigmentary keratitis in brachycephalic dogs is usually driven by chronic irritation from exposed corneas, eyelid abnormalities, dry eye, or poor tear film spreading. It is not primarily an autoimmune disease. The pigment tends to deposit in the lower central cornea where the eyelid rubs, and it is often accompanied by other problems related to the breed's facial conformation.

Pannus, by contrast, is immune-mediated, starts at the limbus, and is strongly linked to breed genetics and UV exposure. The distinction matters because treatment differs. Pannus responds to immune suppression. Pigmentary keratitis is managed by addressing the underlying irritation, which may include surgery to correct eyelid anatomy, tear replacement, or in refractory cases, cryotherapy to remove pigment [10]. A study of 16 corneas in 9 dogs with pigmentary keratitis or CSK found that cryotherapy removed most pigment deposits within 5 to 15 days, but repigmentation occurred when the underlying disease was not controlled [10]. That last point applies to both conditions: you have to treat the cause, not just the pigment.

How Pannus Is Diagnosed

Diagnosis is made by a veterinarian through a complete ophthalmic examination. There is no blood test that confirms pannus.

The examination typically includes:

Schirmer tear test to measure tear production and rule out keratoconjunctivitis sicca (dry eye), which can coexist with pannus
Fluorescein staining to check for corneal ulcers, which would change treatment
Tonometry to measure intraocular pressure and rule out glaucoma
Slit-lamp biomicroscopy to examine the cornea, anterior chamber, and lens in detail
Ophthalmic examination of both eyes, since pannus is usually bilateral

A veterinarian may also examine the third eyelid margin carefully, because depigmentation and thickening there are common in pannus and can be an early clue [6].

In most cases, the combination of breed, history, and characteristic corneal changes (pigment and vascularization starting at the limbus, often in a German Shepherd Dog or Greyhound) is enough to make the diagnosis. If the presentation is unusual, such as a solitary nodule or asymmetric disease, a corneal biopsy may be needed to rule out other conditions [9].

Referral to a veterinary ophthalmologist is reasonable when the diagnosis is uncertain, when the dog does not respond to first-line treatment, or when vision is significantly affected.

Treatment of Pannus in Dogs

Treatment has two goals: reduce active inflammation and prevent the immune system from damaging the cornea again. Because pannus is a chronic autoimmune disease, most dogs need lifelong therapy. Stopping treatment usually leads to relapse.

First-Line Medical Therapy

Topical corticosteroids and topical cyclosporine are the mainstays of treatment. Both suppress the immune response in the cornea.

A study of 41 dogs with CSK treated with a combination of 0.1% dexamethasone and 0.75% cyclosporine with 30% DMSO three times daily found significant improvement after five weeks [11]. The mean number of corneal quadrants affected by neovascularization dropped from 2.63 to 0.24 in the right eye and from 2.66 to 0.59 in the left eye. The mean corneal surface affected by inflammation fell from 53.5% to 26.3% in right corneas and from 54.5% to 30.2% in left corneas. Of 77 corneas with pigmentation, 54 showed reduced pigmentation and 27 showed increased pigmentation [11]. That last number is important: not every dog improves in every measure, and pigment can continue to accumulate even when inflammation is controlled.

Tacrolimus is another option. A study of 16 dogs treated with 0.02% tacrolimus and 50% DMSO three times daily found that the mean corneal surface affected by inflammation dropped from 69.9% to 43.9% in right corneas and from 58.9% to 38.6% in left corneas after five weeks [12]. Of 32 corneas with pigmentation, 14 showed reduced pigmentation and 16 showed increased pigmentation [12]. Tacrolimus reduced inflammation and vascularization but did not consistently reverse pigment.

Pimecrolimus, an ascomycin derivative that inhibits T cell and mast cell activation, has been studied as an experimental treatment. In a small exploratory study of six dogs with CSK, four showed either pronounced improvement (total regression of fibrovascular infiltration, no scarring) or moderate improvement (distinct regression of pannus with mild scarring) when treated with a 1% pimecrolimus corn oil formulation three times daily [13]. The response was unsatisfactory in four of 14 animals across both CSK and dry eye groups [13]. Pimecrolimus is not a standard first-line treatment and is not widely available as an ophthalmic preparation.

What About Steroid Choice and Doses?

The specific drug, concentration, and frequency are decisions for the prescribing veterinarian. Doses are not included here because they depend on the individual dog, the severity of disease, and whether the cornea is ulcerated. Topical corticosteroids should not be used when there is a corneal ulcer, because they can worsen infection and delay healing. Any dog on long-term topical steroids needs monitoring for corneal ulceration and for systemic effects.

Adjunctive and Refractory Treatments

Some dogs do not respond adequately to topical medication. Several options exist for these cases.

Soft X-ray radiotherapy has been studied in dogs with severe CSK that was refractory to prior medical or surgical therapy. In a study of 13 dogs, both corneas were irradiated with soft X-rays (15 kV) to a total dose of 30 Gy given as two fractions over 48 to 96 hours under deep sedation [14]. Three dogs also had superficial lamellar keratectomy 48 hours before radiotherapy. Only minor, transient side effects such as photophobia, epiphora, and blepharitis were noted, and the effect on the course of keratitis was superior to Sr-90 irradiation from a previous study [14]. This is a specialized treatment offered at referral centers.

Cryotherapy has been used to remove refractory corneal pigment. In a study of 16 corneas in 9 dogs with pigmentary keratitis or CSK, most pigment deposits were gone by 5 to 15 days after cryosurgery, though postoperative corneal edema, corneo-conjunctival inflammation, and superficial corneal ulcers occurred in some dogs and resolved by one month [10]. Repigmentation occurred when the underlying disease was not controlled, and a repeat procedure was successful in two dogs [10]. Cryotherapy treats the pigment, not the autoimmune process, so it must be combined with ongoing medical therapy.

Mesenchymal stem cells are an experimental approach. A pilot study of eight German Shepherd Dogs with CSK compared four dogs treated with topical 1% prednisolone to four dogs treated with subconjunctival allogeneic adipose-derived mesenchymal stem cells (1 × 10^6 cells at day 0 and day 30) [15]. Over 110 days, areas of neovascularization, inflammatory infiltrate, and opacity regressed in most eyes in both groups [15]. This is early-stage research and not a standard treatment.

Keratoprosthesis (artificial cornea) has been attempted in dogs blinded by severe corneal disease, including two dogs with CSK. In a study of seven dogs, all regained limited vision after surgery, but purulent keratitis occurred in all five eyes with endothelial disease, requiring removal of the implant in five of seven eyes by six months [16]. This is a last-resort option for severely affected eyes and is not a routine treatment for pannus.

Why Treatment Is Lifelong

Pannus does not go away. The immune system remains primed to attack the cornea, and stopping medication typically allows inflammation to return. Most dogs need some level of ongoing topical therapy, though the frequency may be reduced once the disease is controlled.

Regular rechecks are essential. A typical schedule might involve re-examination every few weeks during initial treatment, then every few months once stable. Your veterinarian will adjust the treatment plan based on what the cornea looks like at each visit.

Living With a Dog That Has Pannus

Several practical steps help owners manage pannus over the long term.

Keep recheck appointments. Pannus can progress silently. A dog that seems comfortable may still have active inflammation that needs treatment adjustment.

Reduce UV exposure. Since UV light is a known trigger, limiting time outdoors during peak sun hours and avoiding high-altitude exposure when possible is reasonable. Dog goggles with UV protection are available, though there is no published evidence in these sources that they change the course of disease. Discuss with your veterinarian whether they are appropriate for your dog.

Watch for changes at home. Note any increase in redness, cloudiness, pigment, squinting, or tearing. Report these at the next visit or sooner if they are sudden.

Do not stop treatment without veterinary guidance. This is the most common reason for relapse. Even if the eye looks clear, the immune process is still present.

Monitor for side effects. Long-term topical steroids can contribute to corneal ulceration, and any new squinting, discharge, or cloudiness should be evaluated promptly. Cyclosporine and tacrolimus are generally well tolerated but can cause local irritation in some dogs.

Limitations and When to Contact a Veterinarian

This article provides general information about pannus in dogs. Every dog is different, and treatment decisions must be made by a veterinarian who has examined the eye.

Contact a veterinarian promptly if your dog:

Develops sudden squinting, pawing at the eye, or reluctance to open the eye
Has a new or worsening cloudy, blue, or red eye
Shows a corneal ulcer or a defect on the eye surface
Has a sudden change in vision, such as bumping into objects or reluctance to navigate stairs
Is on treatment for pannus and the eye looks worse rather than better
Has not had an eye examination in more than six months while on ongoing therapy

Seek emergency veterinary care if the eye is obviously painful, if there is a deep corneal wound, or if the eye appears to be rupturing.

Frequently Asked Questions

What causes pannus in dogs?

Pannus is caused by an immune-mediated attack on the cornea, driven by a combination of genetics and environmental triggers such as ultraviolet light. It is not contagious and is not caused by infection.

Is pannus in dogs painful?

Pannus itself is often not painful in the early stages, which is why it can go unnoticed. Some dogs develop squinting, tearing, or light sensitivity as the disease progresses or when the cornea is ulcerated.

Can pannus in dogs be cured?

No. Pannus is a chronic autoimmune disease that requires lifelong management. Treatment can control inflammation and slow progression, but it does not eliminate the underlying immune process.

Which breeds are most at risk for pannus?

German Shepherd Dogs are most commonly affected. Greyhounds, Border Collies, Australian Shepherds, and Belgian Tervuren also have elevated risk. Brachycephalic breeds like Pugs and Pekingese typically develop pigmentary keratitis, which is a different condition.

At what age do dogs usually get pannus?

In German Shepherd Dogs, the highest incidence is between 5 and 8 years of age, though dogs can be affected earlier or later. Greyhounds are often diagnosed after 4 years of age.

Does pannus cause blindness in dogs?

Pannus can cause blindness if it is not treated, because pigment and blood vessels progressively obscure the cornea. With consistent treatment, most dogs retain useful vision.

Can I stop my dog's pannus medication if the eye looks clear?

No. Stopping treatment usually leads to relapse because the immune process remains active even when the eye looks normal. Any change in medication should be made by your veterinarian.

Is pannus the same as pigmentary keratitis?

No. Pannus is an immune-mediated corneal disease that starts at the limbus and is linked to breed genetics and UV exposure. Pigmentary keratitis is usually caused by chronic irritation from eyelid conformation or dry eye, and it is most common in flat-faced breeds.