🐾 Dry Eye (Keratoconjunctivitis Sicca) in Dogs and Cats – Dr Duncan Houston, Vet 2025

Keratoconjunctivitis sicca (KCS), also known as dry eye, is a condition that leads to dry, inflamed, and uncomfortable eyes in both dogs and cats. Without proper treatment, it can cause vision loss, pain, and irreversible damage. 👁️🐶🐱

💧 Why Tears Are Essential

Tears aren’t just for emotion—they’re crucial to eye health. They hydrate, lubricate, and protect the eye’s delicate tissues. 🧬

• They contain antibacterial proteins and salts. 🦠
• They flush away debris and irritants. 🧼
• They deliver nutrients and remove metabolic waste from the cornea (which has no direct blood supply). 🩸

😢 What Happens Without Tears?

When tear production drops, the result is red, irritated eyes, thick yellow-green discharge, and eventual damage to the cornea (brown discoloration and scarring). Blindness can occur. 🧪

🔍 Understanding KCS

Keratoconjunctivitis sicca literally means “dry inflammation of the cornea and conjunctiva.” It's caused by a deficiency of the water portion of tears (about 95% of tear volume). Left behind is sticky oil and mucus—hence the gooey discharge. 💡

📋 Common Causes of Dry Eye in Pets

• 🐕 Canine distemper – damages tear-producing tissue.
• 🐈 Feline herpesvirus – causes scarring in tear glands.
• 🧬 Congenital deficiency – seen in Yorkshire Terriers.
• 💊 Sulfa drugs – can damage tear glands (e.g., trimethoprim-sulfa).
• 💉 General anesthesia – temporarily suppresses tear production.
• 👁️ Surgical removal of the third eyelid gland – formerly used for cherry eye, now avoided.
• 🧠 Head trauma – affecting the nerves or glands directly.
• 🦴 Immune-mediated gland destruction – the most common cause; particularly in breeds like Cocker Spaniels, Schnauzers, and Westies.

🧪 Diagnosing Dry Eye

It’s not always obvious at first glance. What looks like basic conjunctivitis might be early-stage KCS. Signs include:

• Red eyes and thick discharge 😵
• Crusty eyelids or a dry nose 😓

Schirmer Tear Test is the gold standard diagnostic method. A small paper strip measures moisture in the eye over 60 seconds:

• 📏 15mm+ – normal
• 📏 11–14mm – borderline
• 📏 <10mm – KCS diagnosis
• 📏 <5mm – severe KCS

💊 Treatments for KCS

🌿 Cyclosporine (Optimmune®)

This immune-modulating ointment stops the immune system from destroying tear-producing glands. It’s the most common KCS therapy today and works in up to 80% of dogs—even those with tear scores as low as 2mm. 🧴

• Dosed 1–3× daily
• May take 4–12 weeks to show full improvement ⏳
• Some dogs need compounded higher concentrations 🧪

🧬 Tacrolimus

Used for dogs who don’t respond to cyclosporine. Must be compounded by a pharmacy. Dosed similarly. 📦

💊 Pilocarpine (for neurogenic KCS)

This cholinergic drug is used orally to stimulate glands when nerve signals are absent. Used more rarely. 🧠

💧 Artificial Tears and Lubricants

• Soothing and helpful alongside other treatments
• Some need frequent application—2–12 times per day 🕒

🧫 Topical Antibiotics

Useful early in treatment, when secondary infections are common. Often combined with steroids—unless ulcers are present. 🚫

🩺 Surgical Option: Parotid Duct Transposition

When medications fail, the salivary duct is redirected into the eye to provide a tear substitute. 🧬

Pros:

• Provides constant lubrication
• Useful in refractory cases

Cons:

• Can result in mineral crusting on the eye 💧
• May cause excess tearing during feeding 🐶

This procedure is complex and should be performed by a veterinary ophthalmologist. 🔬

🔄 Follow-Up and Prognosis

After beginning treatment, regular follow-ups every 3–4 weeks are critical for dosage adjustment. KCS usually requires lifelong management. 💉

With good care, most pets live comfortably and retain vision. 👁️❤️

📱 Need Help Managing KCS?

Explore personalized support at AskAVet.com or download the Ask A Vet App for expert guidance, prescription refills, and real-time help from licensed vets! 🐾📲

Authored by Dr Duncan Houston, BVSc – Vet 2025 🐕🐈