Corneal Ulcers in Horses: When to Worry, When to Refer
Recognition and timely management can preserve vision and prevent complications
A horse presents with squinting, tearing, and a red eye. After applying fluorescein stain, you see the telltale uptake that confirms your suspicion: corneal ulceration. But now comes the critical decision. Is this a simple ulcer that will respond to basic treatment, or a complicated case requiring aggressive intervention and possible referral?
According to Dr. Rachel Allbaugh, DACVO, corneal ulceration represents a bulk of equine ophthalmology cases, making pattern recognition and appropriate case stratification essential skills for equine practitioners.¹
Simple Ulcers: The Straightforward Cases
Simple ulcers present with relatively mild clinical signs. The horse may show slight mucoid discharge and minimal epiphora, but the eye appears otherwise quiet. When examined using a slit beam or small circle beam on your direct ophthalmoscope, the corneal curvature appears normal, indicating only epithelial involvement without stromal loss.¹
The surrounding cornea remains clear aside from localized edema. Inside the eye, you may observe mild aqueous flare at most, with pupils remaining mid-range rather than severely constricted. The conjunctiva shows only modest hyperemia.¹
These cases respond well to conservative management. Treatment includes topical antibiotics without steroids (such as neopolybac) three to four times daily, a single dose of atropine at examination, and systemic anti-inflammatory medication like phenylbutazone or flunixin meglumine for a few days.¹
The key to success lies in follow-up. Simple ulcers should heal completely within 3-5 days, as a horse can re-epithelialize an entire denuded cornea within 7-10 days when healthy.¹
Recognizing Complicated Cases
Complicated ulcers present a dramatically different clinical picture that demands immediate attention and aggressive therapy.
Depth assessment becomes crucial. If you observe flattening of the corneal curvature near the ulcer, you’re dealing with superficial stromal involvement. Indentation indicates mid-stromal disease, while severe indentation with fluorescein staining only at the margins suggests a descemetocel, where only microns separate the outer world from the inside of the eye.¹
Infection indicators include cellular infiltrates within the cornea, often appearing as white blood cell accumulation resembling bacterial growth patterns. Dense blood vessel ingrowth (ciliary flush) indicates the process has been ongoing for at least a week, as vessels require 3-5 days to begin growing and advance only one millimeter daily.¹
Melting characteristics represent an ophthalmologic emergency. The cornea may appear jiggly or slimy, resembling “doughnut glaze” in texture. Some cases exhibit a “candle wax” appearance where corneal stroma appears to be melting away. This melting occurs due to enzymes either from bacteria like Pseudomonas or from the tear film attempting to combat infection.¹
Fungal keratitis presents with distinctive features. The classic “cake frosting” appearance involves chunky surface material readily identified on cytology. Another presentation includes deep furrows around islands of fungal material, creating a “moat” effect that prevents corneal blood vessels from infiltrating and healing the area.¹
When General Practice Management Suffices
For complicated cases within your comfort zone, aggressive medical therapy can be highly effective. This includes high-level antibiotics administered 6-12 times daily, with ciprofloxacin and chloramphenicol representing good options for their penetration abilities. Compounded ceftazidime (made by adding 3 cc sterile water to 1-gram vials, then mixing into 15ml artificial tears for 5.5% solution) provides excellent gram-positive coverage.¹
Melting ulcers require anti-collagenase therapy, with autologous serum or plasma being the most cost-effective option. This can be collected from the same horse, spun down, and used at the same frequency as topical medications.¹
Pain management becomes critical, requiring daily atropine (twice daily for severe cases) and systemic anti-inflammatories. Flunixin meglumine at 1.1 mg/kg twice daily for three days, then gradually tapered, represents the preferred systemic choice.¹
For frequent medication administration, subpalpebral lavage lines prove invaluable, allowing owners to deliver medications safely without risk of further trauma.
Red Flags for Referral
Several indicators warrant immediate referral to a veterinary ophthalmologist:
Depth concerns: Any ulcer reaching 50% corneal depth or deeper requires potential surgical intervention.¹
Non-responsive cases: Ulcers showing no improvement or worsening at the 3-5 day recheck, especially with increasing cellular infiltrates or developing melting characteristics.
Melting ulcers: The presence of enzymatic breakdown often benefits from advanced therapies including corneal cross-linking, cryotherapy, or surgical options like keratectomy with grafting procedures.¹
Deep stromal abscesses: When fluorescein-negative lesions present with white blood cell infiltrates trapped within the cornea, creating severe reflex uveitis that threatens vision.¹
The Bottom Line
Early recognition and appropriate case stratification determine successful outcomes in equine corneal ulcer management. Simple cases respond predictably to conservative treatment, while complicated cases demand aggressive intervention and often benefit from specialist involvement.
The key lies in thorough initial assessment, appropriate follow-up, and honest recognition of cases exceeding general practice capabilities. When in doubt, early referral preserves more options for successful treatment than delayed intervention after complications develop.
Dr. Rachel Allbaugh’s insights on equine corneal ulcer management were presented as part of VetOnIt CE’s advanced ophthalmology series. Expand your knowledge of challenging cases with our comprehensive on-demand veterinary continuing education courses.
Tags: Ophthalmology, Equine, Large Animal
References:
- Allbaugh R. Advanced Equine Ophthalmology: Corneal Disease Management. VetOnIt CE Webinar Series. 2024.