Ocular Disease in Horses – Vet Guide 2025 👁️🐴

By Dr Duncan Houston, BVSc

Introduction

Horses possess some of the most sensitive eyes among domestic animals. A watering eye, squinting, redness, or discharge may be harmless in other species—but in horses, these signs demand immediate veterinary attention, as serious infections or ulcerations can cause blindness in mere hours :contentReference[oaicite:2]{index=2}.

Why Quick Vet Involvement Matters

• Speedy progression: Corneal ulcers or infections can deepen rapidly, sometimes rupturing the eye within hours :contentReference[oaicite:3]{index=3}.
• Misdirected home treatment: Over-the-counter ointments—especially those containing steroids—can exacerbate ulcers, invite fungal infections, or mask glaucoma :contentReference[oaicite:4]{index=4}.
• Diverse underlying causes: Conditions like conjunctivitis, keratitis, uveitis, ulceration, glaucoma, tumors, and foreign bodies can all show similar signs yet demand vastly different treatments :contentReference[oaicite:5]{index=5}.

Common Equine Ocular Diseases

1. Conjunctivitis (Red Eye)

Inflammation of the eyelid membranes frequently seen in horses, often seasonally from allergens or flies :contentReference[oaicite:6]{index=6}.

• Signs: redness, mild swelling, watery or mucoid discharge, no squinting in mild cases.
• Vet essentials: check for ulcers, glaucoma, foreign bodies.
• Treatment: topical antibiotics, anti-inflammatories, fly control.

2. Corneal Ulcers & Keratitis

Corneal defects—superficial or deep—are the most frequent and serious eye issues :contentReference[oaicite:7]{index=7}.

• Causes: trauma from grass, bedding, stall walls, hay feeders.
• Signs: cloudiness, intense squinting, excessive tearing, colored discharge.
• Diagnosis: fluorescein dye staining reveals epithelial loss :contentReference[oaicite:8]{index=8}.
• Treatment:
• Superficial ulcers: topical antibiotics, topical/systemic NSAIDs, atropine for pain relief.
• Deep/melting ulcers: aggressive treatment, antifungals, collagenase inhibitors, possible surgery or grafting :contentReference[oaicite:9]{index=9}.
• Protective eye cover, stall confinement, and sub-palpebral lavage if needed.

3. Uveitis & Recurrent Uveitis (ERU)

Inflammation inside the eye—ERU is the top cause of blindness in horses :contentReference[oaicite:10]{index=10}.

• Signs: painful squinting, tearing, cloudy cornea, miosis, photophobia.
• Diagnosis: veterinary exam, tonometry, ultrasound, ruling out ulcers.
• Treatment: topical corticosteroids, atropine, systemic NSAIDs; immunomodulation or surgery in chronic cases.

4. Glaucoma

Increased intraocular pressure leading to cloudiness, pain, and potential vision loss :contentReference[oaicite:11]{index=11}.

• Signs: cloudy eye, squinting, tearing, enlarged globe.
• Diagnosis: tonometry to measure pressure.
• Treatment: pressure-lowering medications—avoid atropine if glaucoma is confirmed.

5. Foreign Bodies & Eyelid Injuries

Hay, grass seeds, or debris can lodge under eyelids—trauma common from stalls, fences :contentReference[oaicite:12]{index=12}.

• Signs: sudden squinting, tearing, discomfort, discharge.
• Diagnosis: vet numbs eyelids and inspects thoroughly using magnification.
• Treatment: removal under sedation, cleanse area, topical antimicrobials.

6. Tumors and Growths

Eyelid or conjunctival masses like squamous cell carcinoma may develop :contentReference[oaicite:13]{index=13}.

• Signs: nodular growths, persistent irritation.
• Diagnosis: biopsy, cytology.
• Treatment: surgical removal, cryotherapy.

7. Hereditary & Age-Related Conditions

Cataracts, glaucoma, night blindness due to congenital or genetic causes are possible :contentReference[oaicite:14]{index=14}.

• Signs: cloudiness, impaired vision.
• Diagnosis: ophthalmic exam, sometimes genetic testing.
• Treatment: monitoring, potential surgery, supportive care.

8. Systemic Disease–Affected Eyes

Diseases like Cushing’s can dampen corneal sensation, delaying signs :contentReference[oaicite:15]{index=15}.

• Owners must be vigilant—subtle redness, tearing in at‑risk horses may mask serious pathology.

Diagnosis: What the Vet Will Do

1. History & ocular signs (squinting, tearing, discharge, cloudiness).
2. Fluorescein stain for corneal defects.
3. Tonometry for pressure measurement.
4. Direct ophthalmoscopy/slit lamp for detailed exam.
5. Cytology/culture on discharge when infection suspected :contentReference[oaicite:16]{index=16}.
6. Ultrasound for internal eye evaluation.
7. Referral to ophthalmologist for surgery or advanced treatment.

Owners Should Never…

• Use over‑the‑counter drops containing steroids without vet diagnosis.
• Delay veterinary care—speed is vital.
• Assume mild symptoms will self‑resolve.

Prevention & Daily Care

• Keep barns and paddocks free from sharp debris.
• Use fly masks, especially during seasons of high fly activity.
• Check eyes daily for tearing, swelling, cloudiness, discharge.
• Limit bright sunlight exposure when using atropine.
• Be extra vigilant with senior or Cushing’s horses.

What Owners Can Do Immediately

• Use warm, clean water to gently flush away debris.
• Note symptom onset, eye affected, and any prior treatments.
• Capture a photo to share with your vet or Ask A Vet for initial assessment.
• Call your veterinarian promptly—describe signs and ask for urgency.

Conclusion

Horses' eyes are prone to rapid, serious issues—from simple conjunctivitis to vision-threatening ulcers, uveitis, or glaucoma. Quick veterinary diagnosis and treatment can often save sight. Never delay or self-medicate—**veterinary guidance is essential**.

See a problem? Reach out to Ask A Vet via AskAVet.com or our app for expert, on-demand help. 📱🩺