Corneal disease of horses (Proceedings)


Scraping for cytology and cultures: The cultures should be done before any drops, (drugs contain bacteriostatic agents), topical anesthetics and the handle end of a scalpel blade to scrape, sterile dacron swabs for culture.


     • Scraping for Cytology and Cultures

          o The cultures should be done before any drops, (drugs contain bacteriostatic agents)

          o Topical anesthetics and the handle end of a scalpel blade to scrape.

          o Sterile dacron swabs for culture.

     • Culture cornea BEFORE applying anything to the eye if overt infection is suspected

          o Aerobic

          o Fungal

     • Fluorescein stain every eye that is PAINFUL!

          o Blepharospasm

          o Epiphora

          o Redness

          o Corneal opacities

     • Rose Bengal Stain

          o Viral Keratitis

          o Early Fungal Keratitis

          o Assess tear film

     • Deep corneal scrapings, at the edge and base of the ulcer to detect bacteria and fungal hyphae

     • Obtained with topical anesthesia and the blunt, handle end of a sterile scalpel blade.

     • Superficial swabbing cannot be expected to yield fungi in a high percentage of cases.

Corneal ulceration

     • Characterize

          o Depth

               • Superficial

               • Deep (Stromal)

               • Descemetocele

               • Perforating

          o Cause

               • Infectious (fungal, bacterial, viral)

               • Traumatic

               • Immune-mediated

          o Duration

               • Response to previous treatments

Superficial ulceration

     • Epithelium only

     • Foals (Increased incidence compared to adults)

          o Corneal sensitivity in foals is very poor.

          o Lower tear production in foals compared to adult's

     • Painful

Stromal ulceration

     • Epithelium and collagen is lost

     • Variation of the clinical picture

     • Descemetoceles

          o Epithelium and stroma are not present

          o Buldge of DM into the defect

          o EMERGENCY!

Corneal rupture

     • Iris Prolapse

          o Is this an EMERGENCY?

     • Owner's Expectations?

          o Cosmetic = Time and $$

          o Enucleation?

     • Treat as if globe is infected

          o Systemic Antibiotics

          o Cannot chance bacterial encephalitis

Bacterial ulcerations

     • Gram Positive

          o Streptococcus -hemolyticus

          o Staphylococcus spp.

          o Corynebacterium spp.

     • Gram Negative

          o Pseudomonas aeruginosa

          o Aspergillus

          o E. coli

     • Treatment Options

          o Gram Positive

               • Triple Antibiotic

                    • Solution or Ointment

               • Chloramphenicol

                    • Ointment

                    • Solution (1 gram vial with 10-15cc of sterile water)

               • Cefazolin

                    • Solution (1 gram vial diluted with 5ml sterile water)

               • Ciprofloxacin

                    • For Staph.

     • Treatment Options

          o Gram Negative

               • Gentocin

               • Solution or Ointment

               • Tobramycin

               • Ciprofloxacin

               • Chloramphenicol

     • UVEITIS

          o Noted with all bacterial ulcerations!

Anti-proteolytic medications

     • N-Acetyl Cysteine 5-10%

          o MOA: MMP Inhibitor : Chelating Ca

          o 5 mL 20% Mucomyst in 15 mL artificial tears

     • EDTA 0.2%

          o MOA: MMP Inhibitor : Chelating Ca

          o 5ml of sterile water to lavender tube (EDTA)

               • If larger tube fill with sterile water until vacuum is gone

     • Galardin (Ilomostat®)

          o Commercially available

          o Antproteinase solution

               • Inhibits MMP1, MMP3 and MMP9

          o Demonstrated in rabbit model to work very well

     • Serum

          o MOA: MMP and serine protease inhibitors

          o Good for 7-8 days refrigerated

          o Cheap!!

     • Tetanus Anti-toxin

          o MOA: MMP and serine protease inhibitors

     • I tend to use 2 anti-proteolytic medications

Fungal infections

     • Aspergillosis and Fusarium

          o Common Fungal isolated in horses

     • Think Fungal Keratitis if:

          o Ulcer is refractory to treatment with topical antibiotics

          o Stromal Melting

          o Lives or has traveled in warm/humid environment

          o Lack of vascularization despite chronicity of ulcer

          o Severe blepharospasm despite small size of ulcer

          o Eye has been treated with steroids

          o Uveitis increases after treatment with antifungals

     • Can be VERY frustrating

     • Can present with a wide variety of appearances

     • Can do whatever they want to – despite appropriate therapy

          o Most likely will need surgical intervention

     • Lots of PMN

          o To small to ingest the hyphae

          o Release LOTS OF PROTEASES

     • Antiangiogentic factors

     • Slow healing

          o 4-6 weeks minimum

     • Topical Treatment

          o Natamycin 3.3 % Solution

               • Take new bottle (5%) and add 7.5cc Sterile water to make a 3.3% solution

               • Produced by Streptomyces spp.

               • Normally found in equine conjunctiva/cornea

               • Most Physiologically appropriate? (per Dr. Brooks)

          o Fluconazole 1%

          o Itraconazole 1% with 30% DMSO Ointment

               • Nice levels in the cornea

          o Miconazole Vaginal Cream

          o SSD

          o Betadine Solution

          o Vericonazole

     • Be aggressive Q1-2 hrs if needed

     • Treat Uveitis

          o Can be severe

          o Flunixin meglumine

          o mg/kg PO or IV BID

          o Atropine Q 4-6 hrs

     • Treat with Antiprotease

     • Treat with broad spectrum antibiotic

          o Neopolybac

     • Repeat Cytology and C/S

          o If the eye first responds to treatment then deteriorates.

     • May have secondary invasion of bacteria

     • GOALS OF THERAPY Resolve Infection

     • HALT Keratomalacia

     • Control Uveitis

          o Dilate Pupil

          o NSAIDS

     • Provide Structural Support

     • Simple Ulcer

     • Neopolybac Ointment

     • Uveitis

          o Banamine

          o Atropine Q8hrs to affect

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