Cyclosporine (also spelled ciclosporin) is a calcineurin inhibitor with potent immunomodulatory properties. In veterinary ophthalmology, it is used topically and as an implant to manage immune-mediated ocular diseases. In horses, cyclosporine has gained significant attention for the management of equine recurrent uveitis (ERU, also known as moon blindness) through the use of a sustained-release suprachoroidal implant. In dogs, topical cyclosporine (Optimmune) is the gold-standard treatment for keratoconjunctivitis sicca (KCS, dry eye) and immune-mediated keratitis.
Overview
Cyclosporine inhibits calcineurin, a phosphatase enzyme critical for T-lymphocyte activation. By blocking calcineurin, cyclosporine prevents the transcription of interleukin-2 and other cytokines that drive the immune-mediated inflammatory response. In ERU, the immune system attacks intraocular structures, causing recurrent episodes of painful uveitis that progressively damage the eye and lead to blindness. Cyclosporine’s immunomodulatory action helps suppress this aberrant immune response within the eye.
Topical cyclosporine (ointment or drops) is effective for surface ocular diseases (KCS in dogs, immune-mediated keratitis) but has limited penetration to the posterior segment of the equine eye. For ERU, the suprachoroidal cyclosporine implant (a sustained-release device surgically placed in the suprachoroidal space) delivers continuous therapeutic drug levels directly to the site of inflammation.
Uses
Horses:
- Equine recurrent uveitis (ERU) — suprachoroidal cyclosporine implant to reduce frequency and severity of recurrent episodes
- Immune-mediated keratitis — topical cyclosporine for corneal immune-mediated inflammation
- Post-uveitis maintenance — ongoing immunomodulation to protect the eye
Dogs:
- Keratoconjunctivitis sicca (KCS / dry eye) — FDA-approved indication for Optimmune; stimulates tear production and reduces immune-mediated lacrimal gland destruction
- Chronic superficial keratitis (pannus) — immune-mediated corneal vascularization
- Immune-mediated keratitis and episcleritis
Dosage
Administered under veterinary or veterinary ophthalmologist direction.
Horses:
| Formulation | Application | Protocol |
|---|---|---|
| Suprachoroidal implant | Surgically placed in the suprachoroidal space | Single procedure; implant provides sustained release for 2-3+ years |
| Topical 0.2% ointment or 1-2% compounded drops | Applied to the eye surface | Every 8-12 hours (for surface ocular disease only) |
Dogs:
| Formulation | Dose | Frequency |
|---|---|---|
| Optimmune (0.2% ointment) | 1/4 inch strip to affected eye(s) | Every 12 hours |
| Compounded 1-2% drops | 1 drop per eye | Every 8-12 hours |
Suprachoroidal implant (horses): This is a surgical procedure performed by a veterinary ophthalmologist, typically under standing sedation with local anesthesia. A small incision is made in the sclera, and the cyclosporine-containing implant is placed in the suprachoroidal space. The implant releases cyclosporine at a sustained rate for approximately 2-3 years or longer, providing continuous immunomodulation at the site of ERU inflammation. Studies have shown that the implant significantly reduces the frequency and severity of uveitic episodes, preserving vision in many horses.
Side Effects
Horses (suprachoroidal implant):
| Common | Serious (Contact Your Vet) |
|---|---|
| Mild post-operative swelling | Implant migration or extrusion (rare) |
| Transient uveitis flare post-surgery | Intraocular infection (endophthalmitis — rare) |
| Retinal detachment (rare) | |
| Continued uveitis episodes despite implant (implant does not cure all cases) |
Horses (topical):
- Mild local irritation
- Generally well tolerated on the ocular surface
Dogs (topical):
- Mild transient stinging upon application
- Local irritation (uncommon)
- Generally very well tolerated; long-term safety is well established
The suprachoroidal implant procedure carries the inherent risks of ocular surgery, though complication rates reported in the literature are relatively low when performed by experienced veterinary ophthalmologists. The most important consideration is that the implant reduces but may not completely eliminate uveitis episodes; ongoing ophthalmic monitoring remains necessary.
Drug Interactions
- Topical ophthalmic atropine: Commonly used concurrently during active uveitis episodes; no adverse interaction with cyclosporine.
- Topical or systemic NSAIDs (flunixin, flurbiprofen): Often used concurrently during uveitis flares; no adverse interaction.
- Topical corticosteroids (dexamethasone, prednisolone ophthalmic): May be used concurrently for acute flares; no direct adverse interaction but monitor intraocular pressure.
- Systemic antifungal drugs (ketoconazole, fluconazole): May increase systemic cyclosporine levels if the patient is also receiving systemic cyclosporine (not typically a concern with ophthalmic-only use).
Contraindications
- Active ocular infection (bacterial, fungal, or viral) in the eye to be treated — immunosuppression may worsen infection
- Known hypersensitivity to cyclosporine
- Implant placement is not appropriate in blind, end-stage phthisical (shrunken) eyes
- Corneal ulceration (relative contraindication for topical use; treat the ulcer first)
Storage
- Optimmune ointment: Store at controlled room temperature. Do not freeze.
- Compounded cyclosporine drops: Follow pharmacy-specific storage instructions (often refrigerated).
- Implant: Stored by the veterinary ophthalmologist per manufacturer guidelines until surgical placement.
Frequently Asked Questions
Can the cyclosporine implant cure equine recurrent uveitis? The implant does not cure ERU but significantly reduces the frequency and severity of flares in most horses. Many horses with implants experience long periods of quiescence and preservation of vision. However, ERU is a lifelong condition that requires ongoing monitoring.
How long does the implant last? Published studies report sustained drug release for approximately 2-3 years, with some implants remaining effective for longer. When an implant reaches the end of its effective life, a new one can be placed.
Is the implant surgery painful for the horse? The procedure is typically performed standing under sedation with local (retrobulbar and subconjunctival) anesthesia. Most horses tolerate the procedure well. Post-operative discomfort is managed with systemic and topical anti-inflammatory medications.
Can topical cyclosporine drops treat ERU? Topical cyclosporine does not penetrate well to the posterior segment of the equine eye, where ERU inflammation occurs. While topical drops may help with surface ocular immune-mediated disease, the suprachoroidal implant is needed for meaningful ERU management.
Is Optimmune used in horses? Optimmune (0.2% cyclosporine ointment) is labeled for dogs with KCS. It can be used on the equine ocular surface for superficial immune-mediated conditions, but it does not reach therapeutic levels in the posterior segment for ERU. Discuss the appropriate formulation with your veterinary ophthalmologist.
This information is for educational purposes only and does not replace professional veterinary advice. Always consult your veterinarian or veterinary ophthalmologist before administering any medication to your animal.