Etiology, Diagnosis, Therapy and the Role of Hypochlorous Acid (HOCl)
Equine keratitis is one of the most common and clinically significant ophthalmic diseases in horses. Due to the prominent position of the equine eye and the horse’s heightened inflammatory response, corneal disease can progress rapidly and may lead to permanent visual impairment or loss of the globe if not treated promptly. A structured diagnostic and therapeutic approach is therefore essential for a favorable outcome.
Equine Keratitis in Horses
Table of Contents
What is equine keratitis?
Equine keratitis is a multifactorial condition and can be broadly classified into infectious and non-infectious forms.
Infectious Keratitis
Most cases are initiated by corneal trauma, allowing microbial invasion. Common pathogens include:
- Bacteria: Staphylococcus spp., Streptococcus spp., Pseudomonas aeruginosa
- Fungi: Aspergillus spp., Fusarium spp. (particularly prevalent in warm, humid environments)
Fungal keratitis (keratomycosis) is especially challenging due to delayed diagnosis, limited antifungal penetration, and prolonged treatment courses.
Non-infectious and Immune-Mediated Keratitis
Immune-mediated keratitis (IMMK) presents as chronic corneal inflammation without epithelial ulceration. Viral involvement (EHV-2, EHV-5) has been proposed, although causality remains unproven.
Clinical signs of equine keratitis
- Blepharospasm
- Epiphora
- Conjunctival hyperemia
- Corneal opacity, edema, or ulceration
- Photophobia
- Corneal vascularization and scarring in chronic cases
Diagnostic Approach
A thorough ophthalmic examination should include:
- Fluorescein staining (and Rose Bengal if indicated)
- Slit-lamp biomicroscopy
- Schirmer tear test
- Tonometry (if uveitis or glaucoma is suspected)
Advanced Diagnostics
- Corneal cytology
- Bacterial and fungal culture
- PCR for viral or difficult-to-culture organisms
- In vivo confocal microscopy (specialized centers)
Therapeutic Management
General Treatment Principles
- Rapid initiation of therapy
- Identification and treatment of the underlying cause
- Pain management
- Prevention of secondary complications
Medical Therapy
- Topical antibiotics (culture-guided)
- Topical antifungals
- Atropine for cycloplegia and pain relief
- Judicious use of anti-inflammatory agents (no corticosteroids in active infection)
Surgical Intervention
- Indicated for deep stromal ulcers, descemetoceles, corneal perforation, or lack of response to medical therapy.
- Options include conjunctival grafts, corneal transplantation, or enucleation in end-stage cases.
The Role of Hypochlorous Acid (HOCl) in Equine Keratitis
Hypochlorous acid (HOCl) is an endogenous antimicrobial compound produced by neutrophils as part of the innate immune response. Stabilized HOCl solutions are increasingly used in veterinary ophthalmology due to their favorable safety profile.
Mechanism of Action
- Broad-spectrum antimicrobial activity (bacteria, fungi, viruses)
- Disruption of microbial biofilms
- Reduction of inflammatory mediators
- Minimal cytotoxicity to corneal epithelial cells
Current Scientific Evidence
While equine-specific clinical trials remain limited, studies in veterinary and human ophthalmology demonstrate that HOCl can reduce microbial load, support wound healing, and serve as a valuable adjunct to conventional antimicrobial therapy. Experimental studies in large animals suggest accelerated healing and reduced pain in infectious keratitis.
HOCl may be particularly useful in:
- Early infectious keratitis
- Adjunctive therapy in fungal keratitis
- Situations where antimicrobial resistance is a concern
- Long-term management where tissue tolerance is critical
Newest study about Equine Ulcerative Keratitis
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