The Ins and Outs of Ocular Trauma in the Horse. Noelle T. McNabb, DVM, DACVO. Peterson and Smith Equine Hospital. Ocala, Florida

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1 The Blown Up Eye The Ins and Outs of Ocular Trauma in the Horse Noelle T. McNabb, DVM, DACVO Peterson and Smith Equine Hospital Ocala, Florida The Prominent Equine Eye Vulnerable to trauma DESPITE protection by: Eyelashes Powerful eyelids Complete bony orbital rim Orbital cushioning by fat, muscle, fascia Common Causes of Ocular Trauma Projectile sand, soil, stones Weed stems, branches Crops & whips Foreign bodies Hay, seed hulls, thorns Hooks, protruding nails, fencing, bucket handles Trailering Types of Trauma Blunt Injury by a solid, round or flat object Sharp Injury by a lacerating object

2 Penetrating Perforating Sedation and Local Nerve Blocks Essential to perform a thorough exam & minimize further ocular injury Detomidine & butorphanol IV Lidocaine or carbocaine CN 7 block (motor) CN 5 (sensory) Blunt Eyelid & Orbital Trauma Lid contusions Blepharoedema Chemosis Orbital hemorrhage & fractures Globe injury is common Orbital Fractures Dorsal orbital rim is most common Can result in displacement, impingement, restriction or laceration of globe Basisphenoid bone of inner orbit Falling over backwards, hitting poll of the head Optic n. and vessel injury Post sedation & nerve blocks palpate orbital rim & wall with lubricated gloved finger CT scan most effective imaging Blunt Globe Trauma Possible sequela: Corneal ulceration

3 Scleral, limbal, and /or corneal rupture Uveitis, hyphema, glaucoma Lens luxation, cataract Retinal tears & detachment Vitreal hemorrhage Proptosis is uncommon without orbital fractures & profound globe injury Phthisis bulbi Blunt Eyelid & Orbital Trauma Treatment Topical Abs +/- corticosteroids * *1 st ensure flouro negative & complete lid closure Lubricants Systemic flunixin meglumine: 1 mg / kg BID to start ABs if obvious fractures Severe periorbital fractures or SQ emphysema Temporary tarsorrhaphy Seek comprehensive ophthalmic evaluation with imaging Globe Rupture Eye filled with incompressible liquid Rapid rise in IOP Eyewall yields at its weakest point Limbus Equator Ultrasound Dx

4 When to Consider Immediate Enucleation Optic nerve severed Globe ruptured & collapsed When extent of damage cannot be assessed: Temporary tarsorrhaphy Seek comprehensive ophthalmic evaluation with imaging Positive Predictors of Visual Outcome & Ocular Survival After Iris Prolapse Positive consensual PLRs Minimal to no hyphema Corneal lacerations < 15 mm Ulcerative keratitis < 15 days *Chmielewski (McNabb) N.T., et al. (1997) Visual outcome and ocular survival following iris prolapse in the horse: a review of 32 cases. Equine vet. J. 29, Negative Predictors of Visual Outcome & Ocular Survival After Iris Prolapse Corneal lacerations >15 mm in length Extension to, along or beyond the limbus Ulcerative keratitis > 15 days Keratomalacia Total hyphema Iridectomy Does not adversely affect outcome Principles of Eyelid Laceration Repair Upper lid and nasal wounds are more serious than lower lid injuries Eyelids have robust blood supply

5 Preserve eyelid margins Principles of Eyelid Laceration Repair Treat promptly to avoid: Tissue contraction Desiccation Infection Loss of function Remove debris with copious saline flushing Minimal tissue margin debridement Principles of Eyelid Laceration Repair 2-3 layer tissue closure Skin Tarsus (holding layer) & SQ 4-0 to 5-0 absorb. suture Polyglactin (Vicryl) Polyglycolic acid (Dexon) 4-0 to 5-0 Prolene, Nylon Precisely appose eyelid margins Figure-8 suture pattern Unrepaired Lid Margin Lacerations Unrepaired Eyelid Lacerations reconstruction Corneal Trauma Superficial abrasion to full-thickness perforation with iris prolapse

6 Post-traumatic infection is always of major concern Corneal Ulceration Fluorescein stain ALL eyes post trauma Rose bengal Diagnostics: 1 st : Swab ulcer for aerobic & fungal culture 2 nd : Collect cytology Infectious Organisms in Equine Ulcers Bacterial Pseudomonas aeruginosa Streptococcus equi Staphylococcus aureus Fungi often filamentous, septate Fusarium Aspergillus, Penicillium Cladosporium, Cylindrocarpon Alternaria, Curvularia Corneal Cytology Topical proparacaine or tetracaine Collect scrapings using blunt end of scalpel blade Therapy for Superficial Corneal Ulcers & Minimal Stromal Loss Topical ABs : 4-5 times daily Neopolybac oint, Neopolygram, tobramycin, ofloxacin soln Atropine: q 4 hrs until dilates, then dose to maintain Autologous serum: 4-5 times daily

7 Systemic NSAIDs for uveitis Flunixen meglumine 1 mg /kg BID daily to start Assess eye within hrs for collagenolysis ( melting ) Fungal Keratitis Hyphae positively identified on cytology or culture Also suspect when: Recent therapy with topical steroids Follows prolonged topical AB use Assoc. with plant material Antifungal Therapy Topical: start 6-8 times daily Miconazole, itraconazole, natamycin, ketoconazole, fluconazole, silver sulfadiazine Voriconazole refractory to above or progressive infection Uveitis may worsen day after starting antifungals due to fungal death Systemic fluconazole : 5 mg / kg QD Itraconazole: 3 mg / kg BID Melting Ulcers Proteinases from keratocytes, PMNs and microbes result in stroma collagenolysis Ulcers often progress despite effective AB therapy Inflammatory enzymes persist within sterilized wounds Combination of ABs and antiproteases will stabilize cornea and improve clinical response Stabilizing Collagenolysis Topical serum with alpha 2 macroglobulins inhibits: matrix metalloproteases (MMP)

8 serine proteases (NE) Acetylcysteine 5% EDTA 1% inhibits MMP Doxycycline inhibits MMP Melting Corneal Ulcers Warrants aggressive and /or surgical therapy based on cytology and culture Cefazolin (55 mg/ml) if beta hemolytic Strep. q 2 hrs Tobramycin / gentamicin & ciprofloxacin if Pseudomonas q 2 hrs Voriconazole if + for hyphae q 4 hrs Atropine q 4 hrs until dilated Serum, EDTA, & acetylcysteine q 1-2 hr Systemic NSAIDs 1 mg /kg BID Systemic doxycycline: 10 mg /kg PO QD Keratectomy and corneal grafting Subpalpebral Lavage Indications: Protective Eye Wear Equine Eye Saver Mask Deep or progressive corneal ulcers High frequency medications required Pain or temperament power lock eyelids Post-op care of fragile eye Surgical Therapy for Ulcerative Keratitis Keratectomy removes necrotic stroma and microbial debris

9 Speeds healing, reduces scarring and stimulus for iridocyclitis Grafting techniques: Conjunctival flap BioSISt Amnionic membrane Penetrating keratoplasty Conjunctival Grafts *permits evaluation of AC *post-op temporary tarsorrhaphy *requires general anesthesia & precise surgical technique Amniotic Membrane Grafts Thick basement membrane Stroma contains antiproteases thereby reducing melting and vascularization Amnion Transplants Can be used alone or with conjunctival grafts Suppresses TGF- beta & myofibroblast differentiation thereby reducing scarring Surgical Repair of Corneal Lacerations Small perforations can self-seal with uveal tissue & heal with pupil deformation, synechia and scar Indications for repair: Corneal Laceration Repair: Direct Suturing > 50% corneal depth Perforations > 2 mm +/- iris prolapse Corneal Laceration Repair: Direct Suturing

10 Corneal Laceration Repair Direct Suturing & Conjunctival Graft Traumatic Uveitis Miosis, low IOPs, aqueous flare, fibrin in AC Synechia, cataract and persistent corneal edema are common sequela Hyphema has a good prognosis if fills < 1/3 of AC Treatment for Traumatic Uveitis Restrict exercise to prevent recurrent bleeding Topical corticosteroid & ABs 1 st ensure negative fluor. retention Neopolydex, Tobradex, or Maxitrol: 4 5 times daily Topical atropine: q 4 hrs until dilates then dose to maintain Minimizes synechia, pain and helps stabilize BAB Systemic NSAIDs Flunixin meglumine: 1 mg / kg daily to start Tissue plasminogen activator (TPA): intracameral ug Lysis of large fibrin clots in the AC Traumatic Uveitis Hyphema with fibrin 7 days into therapy Traumatic Uveitis Corneal endothelial injury, edema & miosis 7 days later: some edema persists Lens Displacement Subluxated to luxated Occurs with blunt or perforating eye injuries

11 Cataract often forms days to weeks later Indications for lens removal: glaucoma corneal contact & edema lens capsule rupture phacoanaphylaxis Lens Subluxation Traumatic hyphema 4 wks later: aphakic crescent more prominent Posterior Lens Luxation Lens displaced posteriorly into the vitreous body Vitreal hemorrhage and inflammation Vitreal retinal traction bands form Can result in retinal tears & detachment if did not already occur with initial trauma Retinal Injuries Edema Hemorrhage Tears Detachment Degeneration Ocular ultrasound Ideal method to evaluate retina post-trauma Retinal Tears & Detachment Etiologies Blunt (closed globe) trauma

12 Globe perforation & rapid drop in IOP Acute blood loss Vitreal-retinal traction bands Retinal degeneration / thinning Hypotony Chronic uveitis Optic Nerve injury After Head Trauma Stretching, bruising, shearing & avulsion of nerve & associated vessels Dilated (Marcus Gunn ) pupil Absent direct & consensual PLR Acute Treatment Systemic corticosteroids and DMSO Blindness often permanent Post Traumatic Optic Nerve Atrophy Pathogenesis poorly understood Shearing forces at optic foramen from brain displacement post head trauma Direct nerve injury, disrupted blood supply, subarachnoid hemorrhage & optic canal fractures likely contribute

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