Keratoconjunctivitis sicca, or KCS, is immune-mediated destruction of the tear glands and is the most common cause of chronic red, gunky eyes in dogs. Roughly 1 in 22 dogs in large retrospective studies are diagnosed at some point in life, with Cavalier King Charles Spaniels, English Bulldogs, Cocker Spaniels, West Highland White Terriers, Shih Tzus, and Lhasa Apsos at the highest risk (Sanchez et al., 2018, Vet Ophthalmology). Twice-daily cyclosporine or tacrolimus eye drops control most cases for life, but untreated KCS progresses to corneal ulceration, pigmentation, and vision loss.
Last reviewed: June 2026
What Dry Eye Actually Is
Keratoconjunctivitis sicca is a chronic deficiency of the aqueous layer of the tear film, almost always caused by immune-mediated destruction of the lacrimal and third-eyelid glands. Without enough tears, the cornea dries and the conjunctiva becomes inflamed, producing the classic thick, ropy, yellow-green discharge owners notice first. The disease is bilateral in roughly 80 percent of dogs, though one eye is often worse early on. As described in Slatter's Fundamentals of Veterinary Ophthalmology, sustained tear-film deficiency causes corneal pigmentation and neovascularization within weeks to months, which is why a dog with chronic gunky eyes deserves a Schirmer tear test at the first visit.
Signs Owners See
The earliest signs are subtle: a small amount of mucoid discharge in the inner corner each morning, slight conjunctival redness, and a dull rather than glistening corneal surface. As the disease advances, discharge becomes thick, ropy, and yellow-green; the dog may rub the eyes on furniture; the cornea darkens with brown pigment from chronic irritation; and superficial ulcers form. Many owners are sent home repeatedly with antibiotic drops that fail to control the discharge because the underlying problem is tear deficiency, not infection.
Diagnosis: The Schirmer Tear Test
Diagnosis is fast, inexpensive, and definitive. A standardized paper strip is hooked into the lower conjunctival sac and the moisture absorbed in 60 seconds is measured. Normal dogs produce more than 15 mm per minute; values 10 to 15 are borderline; 5 to 10 reflect mild to moderate KCS; below 5 mm per minute is severe disease (Best et al., 2022, Vet Ophthalmology). Tear film breakup time and fluorescein staining to look for ulcers complete the workup. Underlying causes worth ruling out include canine distemper exposure, sulfa drug reactions, congenital alacrima in Yorkshire Terriers and Pugs, and surgical removal of the third eyelid gland (cherry-eye misadventure).
Treatment That Works for Decades
The cornerstone treatment is a topical immunomodulator — most commonly cyclosporine 0.2 to 2 percent or tacrolimus 0.02 to 0.03 percent — applied to each eye twice daily for life. Cyclosporine increases tear production in roughly 75 to 85 percent of treated dogs within 4 to 8 weeks. Artificial tears every 4 to 6 hours during the day support the eye while the immunomodulator takes effect. Topical antibiotics are added only when secondary infection or ulceration is present. Pilocarpine is an option in cases where the lacrimal gland is denervated rather than destroyed. Surgical parotid duct transposition redirects salivary flow to the eye and is reserved for dogs that fail medical therapy.
What Happens If You Skip Treatment
Chronic untreated KCS leads to a predictable cascade: corneal pigmentation that obscures vision, recurrent superficial ulcers that fail to heal, deep stromal ulceration, descemetocele, and ultimately corneal rupture. Pigmentary keratitis once established is largely irreversible — even with treatment, vision lost to dense central pigment usually does not recover. The dog you treat early stays comfortable with a faintly red eye and morning discharge that an immunomodulator drop quietly controls. The dog you treat late lives with brown corneas, chronic discomfort, and a real risk of losing an eye.
When to See a Vet
Call your vet today if:
- Thick yellow-green discharge in one or both eyes for more than 3 days
- Repeated bouts of "conjunctivitis" that come back when antibiotic drops stop
- A high-risk breed (Cavalier, Bulldog, Cocker, Westie, Shih Tzu, Lhasa) with red eyes
- Visible brown pigment creeping in from the edge of the cornea
- Squinting or rubbing the face on furniture without improvement in 24 hours
Go to the ER immediately if:
- A blue or white cloudy spot on the cornea (suggests stromal ulcer or descemetocele)
- A sudden bulging or deformity of the eye
- A dog holding the eye shut, with the third eyelid up and obvious pain on light touch
- Sudden cloudiness with thick discharge and squinting in a dog already known to have KCS
- Vision loss, including bumping into walls, in any eye that has been chronically red
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Frequently Asked Questions
Why didn't my regular antibiotic drops fix this?
Because the underlying problem is tear deficiency, not bacterial infection. The discharge is a downstream consequence of a dry surface and inflamed conjunctiva. Antibiotic drops may control overlying bacteria briefly, but as soon as you stop, the cycle returns. Specific treatment is an immunomodulator like cyclosporine or tacrolimus to restore tear production.
How much does dry eye treatment cost?
Initial vet exam plus Schirmer tear test typically runs $75 to $200 in the US. Compounded cyclosporine 1 to 2 percent eye drops cost $40 to $90 per bottle and a bottle lasts about 4 to 6 weeks per dog. Tacrolimus 0.03 percent is similar. Annual treatment cost averages $300 to $800 plus 2 vet rechecks. A board-certified veterinary ophthalmology referral runs $200 to $450. Parotid duct transposition surgery for medication-failure dogs is $2,500 to $5,000+. Catching it early prevents a lifetime of pigmentary keratitis and corneal ulcer hospitalizations.
Can I use over-the-counter human dry-eye drops?
Lubricant artificial tears made for humans are safe to use in dogs and help between cyclosporine doses, but they do not treat the underlying disease. Drops containing vasoconstrictors (Visine and similar) should never be used because they worsen irritation. Choose preservative-free single-dose vials if you are using them frequently. The treatment that changes the disease course is a topical immunomodulator your vet prescribes.
Does cyclosporine have side effects?
Topical cyclosporine has an excellent long-term safety profile in dogs. Mild local irritation in the first week is common and usually self-resolves. Systemic absorption is minimal and does not affect immune function. Some dogs need a brief course of artificial tears to bridge the 4 to 8 week ramp-up while cyclosporine takes effect. Dogs on long-term cyclosporine should still have annual Schirmer tear tests to confirm the dose is working.
Will my dog go blind from dry eye?
If treated early and consistently, the great majority retain functional vision for life. Vision loss occurs in dogs with dense corneal pigmentation from untreated disease, in dogs that develop a deep ulcer or perforation, and in dogs whose owners cannot maintain twice-daily drops. Twice-daily lifelong dosing is the price of preserving vision — once you and the dog establish a routine, most dogs accept it readily.
Still Not Sure if Your Dog Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of the discharge and cornea in good lighting, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.