Equine Ophthalmology · Field Guide

Corneal ulceration, stromal abscess & topical regimen — diagnostic thresholds & therapy for the ambulatory equine clinician
QR-041 · v2 Front · 1 of 2 Vet On It
Stain every painful eye.
Fluorescein on every presentation for ocular pain — before any therapy. Most present with ulceration, not foreign body. Hydropulse foreign bodies with 6 cc syringe + 18-ga needle broken at hub. Exam in a dark setting (barn lights off, or blanket tent).
Simple ulcer
Superficial epithelial defect · slit-beam: no indentation, clear stroma · no infiltrate or melting · heals in 5–7 d · recheck 3–5 d
Complicated
Any melting, white-cell infiltrate, stromal loss ≥50%, reflex uveitis, or ulcer unchanged/worse at 48–72 h — intensify & refer
Never
Topical steroid on any fluorescein-positive eye — potentiates collagenase & perforation · never grid keratotomy (opens to seeding)

01Corneal ulcer — depth, triage, actionslit-beam assessment · sample with Kimura spatula or blunt scalpel · never cotton swabs

DepthSlit-beam & appearanceDiagnosticsAction
SuperficialEpithelial
 Focal fluorescein uptake · no stromal indentation · clear surrounding stroma. Otherwise quiet eye, mild conjunctival hyperemia Fluorescein + full exam. Cytology not required if uncomplicated. Rule out foreign body under 3rd eyelid + fornices Simple regimen. Broad-spectrum topical q6h, atropine ×1 (then PRN miosis), systemic flunixin 1.1 mg/kg. Recheck 3–5 d. If unchanged, reclassify
Mid-stromalPartial loss
 Indentation on slit-beam · gray/white cellular infiltrate · reflex miosis · infected if cake-frosting or moat-ring appearance Cytology + C/S before first dose · Diff-Quik for bacteria / fungal hyphae. Cytology > culture for empiric choice Complicated regimen. Fortified abx q1–2h, voriconazole q2h if endemic/hyphae, serum q1–2h, atropine, flurbiprofen. Place SPL line. Refer if not improving
Deep>50% stroma
 Descemetocele risk · significant indentation · central dark area · floor stain-neg, margin stain-pos Cytology + culture + fungal search (branching hyphae in PMN mats). Do not delay therapy for culture Refer same-day. Bridge: SPL line, fortified abx q1–2h, voriconazole q2h, serum q1–2h, atropine BID, flunixin. Consider systemic abx/antifungal
MeltingAny depth
 Gelatinous, jiggly stroma on cytology · candle-wax gravitational flow · may be non-infectious (MMP-driven) in young horses Cytology to rule out infection — treat as emergency regardless of result Anti-collagenase. Autologous serum/plasma q1–2h (re-collect every 5–7 d) + EDTA or N-acetylcysteine + doxycycline. Corneal cross-linking if available
Stromal abscessStain-negative
 Focal yellow/white stromal infiltrate with intact epithelium · severe reflex uveitis is the chief threat · fluorescein negative Clinical Dx — no open surface. Assume bacterial + fungal co-infection until disproven Penetrating abx. Ofloxacin/chloramphenicol 6–8×/d + voriconazole 6–8×/d via SPL · systemic abx + antifungal · atropine BID–QID. Intrastromal voriconazole or DLEK if not resolving

02Topical & systemic regimenwait ≥5 min between drops · antiprotease last · 2–3 cc air flush via SPL between drugs

Ofloxacin · Chloramphenicol · CiproGram ±
Simple: q6h · Complicated/abscess: q1–2h via SPL (6–10×/d)
Chloramphenicol + ofloxacin penetrate intact epithelium best — first line for stromal abscess. NeoPolyBac solution (no dex) is a commercial triple alternative.
Fortified cefazolinGram+ cocci
1 g vial + 3 cc sterile water; all 3 cc into 15 mL artificial tears → ~55 mg/mL (5.5%) · refrigerate, 2-wk BUD · q1–2h via SPL
Add when cytology shows gram-positive cocci.
Voriconazole 1%Antifungal · 1st line
1 drop q2h via SPL · source 1% IV formulation from human pharmacy — not ophthalmic
Cake-frosting surface or moat-ring = empirically fungal. Miconazole / natamycin acceptable if unavailable. Silver sulfadiazine cream between eyelids for money cases.
Autologous serum / plasmaAnti-collagenase
Centrifuge whole blood → serum (or purple-top → plasma) · q1–2h · re-collect every 5–7 d · give last in sequence
Alternatives: EDTA, N-acetylcysteine, doxycycline systemic. Diluted Betadine 1:50 AM/PM flush cleans line + eye.
Atropine 1%Cycloplegic
BID until mydriasis, then PRN (typ. q12–24h) · stabilizes blood-aqueous barrier · blocks ciliary spasm
Monitor colic — daily appetite + fecal output. Stop at first drop — early withdrawal prevents progression.
Flurbiprofen 0.03% + FlunixinNSAID topical + systemic
Flurbiprofen q6h topical · Flunixin 1.1 mg/kg IV/PO BID ×3 d, then taper. Phenylbutazone 2 g BID acceptable
Flurbiprofen is the stain-positive NSAID — use when steroid contraindicated. Full-dose flunixin >3 d common in complicated cases.
Vet On It Vet On It CE · Clinical Resource Library
Derived from Advanced Equine Ophthalmology webinar · RACE/AAVSB approved · QR-041 · printed Mar 31, 2026 · Front 1/2
Scan to register for Advanced Equine Ophthalmology — events.vetonitce.org/event37 Register
Vet On It CE Disclaimer: Vet On It CE provides these materials as a courtesy summary derived from lecture content. These materials are for educational reference only and do not constitute veterinary medical advice, diagnosis, or treatment recommendations. They do not replace clinician judgment, patient-specific assessment, or applicable local regulations/formulary guidance.

Equine Ophthalmology · Field Guide

Uveitis / ERU, immune-mediated keratitis & ocular surface neoplasia — workup, therapy & referral thresholds
QR-041 · v2 Back · 2 of 2 Vet On It

03Uveitis · ERU workupaqueous flare is the hallmark — direct ophthalmoscope, tiny-circle beam held close, view from the side

Technique for aqueous flare: direct ophthalmoscope on smallest circle (not slit), held ≈1 cm from eye, observer views from 90° to the beam — look for a headlight-in-fog column between cornea and lens. Full dark setting required. Other findings: ventral KPs, hypopyon, posterior synechiae, iris hyperpigmentation, rubeosis irides, cataract, yellow-green "pond-water" vitreous. IOP low in active uveitis; if normal/high, suspect secondary glaucoma.

Workup — first episode
  • Full exam · stain first — rule out primary ulcerboth eyes
  • Slit-beam ± tropicamide dilationdark setting
  • CBC / chemistrybaseline
  • Leptospira serologyserum
  • Aqueous humor tap — aq:serum AbC-value definitive
  • IOP by tonometrylow in uveitis
Predisposed breeds — low workup threshold
AppaloosaPony of AmericasWarmbloodDraftPaint
Treatment — active flare · taper 2–4 wk past signs
  • Prednisolone acetate 1%q6h · stain-neg only
  • Dexamethasone alcohol (NeoPolyDex)penetrates, stain-neg
  • Flurbiprofen 0.03%stain-pos alternative
  • Atropine 1%BID → PRN
  • Flunixin 1.1 mg/kg BIDsystemic · 1st line
  • UV-blocking fly maskGuardian / EquiVisor
ERU maintenance & rescue
  • Diclofenac 0.1% BIDchronic taper
  • Intravitreal low-dose gentamicinnon-Appaloosa
  • Suprachoroidal cyclosporin implantAppaloosa · 14–16 mo

04Immune-mediated & eosinophilic keratitischronic stain-neg · cytology before steroid

Entity
Recognition & therapy
Eosinophilic keratitisLate summer / fall
Yellow raised gritty plaque ± superficial ulcer · cytology: eosinophils. >⅓ develop 2° bac/fungal co-infection. Rx: topical abx ± antifungal q6h, atropine BID, systemic prednisolone (avoid if Cushing's). Cetirizine + deworm for recurrence. Courses 1–2+ months.
IMMK — superficial / mid-stromalStain-negative
Chronic epithelial/stromal infiltrate ± vessel ingrowth. Rx: topical pred acetate or cyclosporine (Optimmune) q6–12h; topical NSAID if steroid unsafe. Early episcleral cyclosporine implant (NCSU pharmacy, 14–16 mo) — often permits drug-wean.
IMMK — endothelialDeep · edema
Corneal edema (pump failure) ± bullae. Add NaCl 5% topical to draw fluid; continue immunosuppressive. Watch bulla rupture → 2° ulcer. Chronic IMMK carries corneal-lymphoma risk (6+ yr) — biopsy atypical progression.

05Ocular surface neoplasiadebulk + adjunctive · recheck q6mo lifelong

Tumor
Recognition
Treatment
SCCMost common
Red/pink limbal or 3rd-eyelid mass. Not every red/pink mass is SCC — biopsy atypicals. Palpate posterior margin under topical anesthesia.
Keratectomy + conjunctivectomy + adjunctive: cryo, CO₂ laser, strontium-90, PDT. Topical mitomycin C QID ×1wk on / 1wk off ×4 cycles.
SarcoidPeriocular
Verrucous/nodular peri-orbital lesion · biopsy / manipulation may provoke aggressive regrowth.
Do not debulk without defined adjunctive plan. Cryo or intralesional preferred; refer.
Mast cellLess common
Nodular conjunctival mass — confirm cytology/biopsy.
Surgical excision with margins; recurrence possible.
Hemangio-sarcomaConjunctival/scleral
Red fleshy conjunctival/scleral mass, may bleed on handling.
Keratectomy / conjunctivectomy + cryo or laser. Monitor local + distant recurrence.
Granulation (post-op)CO₂ laser mimic
Smooth rounded post-excision regrowth — not SCC recurrence.
Topical neopolydex 3–4×/d until resolved. UV mask (Guardian / EquiVisor, ~90% UV) lifelong.
Refer

Same-day: melting ulcer · descemetocele · deep stromal loss ≥50% · unresponsive uveitis · suspected endophthalmitis · ruptured globe (unless stable on medical) · stromal abscess not responding · any painful eye worsening at 48 h · any horse the owner cannot medicate 6–10×/d. Never place a 3rd-eyelid flap or tarsorrhaphy on a complicated eye — hides monitoring.

Clinical pearls
  • SPL line — 12-ga trocar through lower-eyelid fornix; seat footplate deep so it cannot contact cornea.
  • Drop spacing — ≥5 min between topicals; antiprotease last; air flush via SPL.
  • Seidel test — concentrated fluorescein (no rinse) + cobalt light; aqueous dilution = rupture.
  • Rupture prognosis — >15 mm, crosses limbus, no dazzle/consensual PLR, lens rupture = poor.
  • Calcific band keratopathy — steroid-driven · stop steroid; start topical EDTA + NSAID.
  • "Bullet-hole" retinal lesions without active signs do not warrant workup.
Vet On It Vet On It CE · Clinical Resource Library
Derived from Advanced Equine Ophthalmology webinar · RACE/AAVSB approved · QR-041 · printed Mar 31, 2026 · Back 2/2
Scan to register for Advanced Equine Ophthalmology — events.vetonitce.org/event37 Register
Vet On It CE Disclaimer: Vet On It CE provides these materials as a courtesy summary derived from lecture content. These materials are for educational reference only and do not constitute veterinary medical advice, diagnosis, or treatment recommendations. They do not replace clinician judgment, patient-specific assessment, or applicable local regulations/formulary guidance.