Disease Du Jour: Equine Ophthalmic Emergencies

Veterinarians can gain a lot of tips from listening to Dr. Ann Dwyer on Disease Du Jour's Ophthalmic Emergencies podcast.

Veterinarians can gain a lot of tips from listening to Dr. Ann Dwyer on Disease Du Jour’s Ophthalmic Emergencies podcast. iStock

In Episode 70 of the Disease Du Jour podcast, we visit with Ann Dwyer, DVM. She has practiced at Genesee Valley Equine Clinic in New York since earning her veterinary degree from Cornell in 1983. During her career, she has pursued interests in equine ophthalmology. She lectures nationally and internationally and has published multiple papers and book chapters on equine ophthalmology, including Ophthalmic Emergencies in the Field published this year. In 2012 she was named an honorary member of the American College of Veterinary Ophthalmology. Dwyer served as the 2013 AAEP president and is currently vice chair of the Advisory Council for the veterinary college at Cornell, is a member of the Cornell Zweig Committee that allocates funds for equine research, and she is on AVMA’s Council on Education.

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EquiManagement’s Disease Du Jour podcast is focused on equine research and current best practices. Disease Du Jour is brought to you in 2021 by Merck Animal Health.

Topics

1. How does an owner know that a horse has an ophthalmic emergency?

  • May be obvious (eyelid tear, facial trauma)
  • Swollen, closed, tearing eye that resents handling.
  • Change in appearance: Area on eye looks white, yellow, blue or red.

2. How common are emergencies involving the eye in equine practice?

  • VERY common. In one year in our 5 DVM practice, 16% of all emergencies (98/615 in her practice). 
  • In northeast, uptick in fall months: July to October, 21% emergencies (49/229)

3. What are the most common problems that prompt an urgent visit?

  • Three common urgent problems accounted for 557 ocular emergencies in our practice over 6 years: 380 corneal ulcers, 120 acute swollen eyelids that did not have an ulcer, 57 eyelid tears.
  • After that there is a long list of less frequent problems like stromal abscess, ERU, glaucoma, foreign body, orbital fractures, etc.

4. What kind of supplies and equipment does an ambulatory equine vet need to have in their truck to treat equine eye emergencies?

  • General purpose supplies: NSAIDs, sedatives, local anesthetics, sutures (4-0 especially)
  • Direct ophthalmoscope with transilluminator. OPTIVISOR (Jeweler’s device) BRIGHT LIGHT (military flashlight, headlamps), tonometer. +/- slit lamp, indirect lens.
  • CAMERA!
  • Dedicated tote box advised for specialty supplies
    • Topical mydriatic, anti-infective, anti-collagenolytic, hyperosmotic, steroids and NSAIDs
    • Stain strips, STT, SPL kits, tubes to flush NL ducts
    • Individually packaged ophthalmic instruments: bishop harmon and small adson forceps, small mosquito hemostats, Stevens tenotomy scissors. I use small Olsen Hegar needle holders, not ophthalmic holders in the field
    • Plenty of 4-0 suture. Absorbable OK—Vicryl, PGS.

5. Most equine eye emergencies are seen on the farm. What can be done to the stable environment to optimize conditions for examination and treatment?

  • Create a dark, uncluttered area, free of junk. May need to drape windows/doors
  • Hay bale table with blanket covering it, or recycling bin to use as table
  • Block wind, reduce disturbances
  • Space to set up tables or provide trunks as tables.

6. Eye problems are often painful, making examination a challenge. How do you provide regional anesthesia and sedation in the field?

  • Xylazine for minor sedation. Detomidine for major. 1 cc of Ace to start helps.
  • Auriculopalpebral nerve block to effect motor paralysis of upper eyelid. 3 sites, 25G 5/8” needle, 2 ml local.
  • +/- Supraorbital nerve block to reduce sensation of globe
  • Topical anesthesia—proparicaine
  • If topical not working, give 0.25 ml mepivicaine subconjunctivally—GAME CHANGER.

7. Describe the examination process.

  • Do full exam of BOTH eyes even if problem is very obvious
  • Start with whole horse, vitals, check for co-morbidities
  • Cranial nerve exam, testing PLR, menace, dazzle, blink, VII
  • Then proceed in checklist fashion, outside to inside. Use bright light +/- magnification to inspect skull, adnexa, conjunctiva, cornea, anterior chamber, drainage angle, iris, NOTE PUPIL SIZE. Then lens, vitreous and fundus.
  • Transilluminator can be the #1 tool as long as pupil is open enough to see through.
  • Use advanced equipment (tonometer/SL) if you have it.

8. What kind of diagnostic tests and imaging are commonly indicated?

  • Fluorescein stain of cornea
  • Cytology of cornea if disrupted
  • PHOTOGRAPHY
  • +/- periocular ultrasound (not often but can use field equipment)

9. Let’s go through common problems, starting from the outside of the eye and progressing inwards. What are the most common emergencies affecting the eyelids and periocular region? Treatment tips for these problems?

  • Trauma around the eye-Blunt (screen for orbital fracture, treat for sinus fracture) or sharp (repair promptly, heals well).
  • Acute eyelid swelling—could be allergic (minor) or secondary to globe problem, especially corneal ulcer. CHECK PUPIL SIZE.
  • Eyelid tears
    • Bucket handles are #1 cause!!!
    • CAREFUL repair, two layers, use small suture, study techniques for margin apposition.

10. Moving onto the globe itself, (a)what is the most common emergency affecting the ocular surface (cornea)? And (b) what kind of treatment is appropriate for disruption of the ocular surface?

  • Corneal ulcer
  • Debridement, Pupil dilation with atropine, NSAIDs for all cases
  • Other topicals dependent on etiology which usually is NOT obviou—empiricals prescribed, then modify when cytology diagnostics are done
    • Infections: Bacteria, Fungal
    • Immune related inflammation: EK
    • Collagenolysis: lots of PMNs
    • Foreign body
    • Indolent

11. What diagnostic tests are indicated if the corneal surface is disrupted?

  • Fluorescein staining coupled with photography
  • Cytology, easily performed in field. Follow with debridement. Staining and interpretation should be done IN HOUSE for prompt results. Culture more chronic ones
  • Modify treatment appropriately

12. Moving INSIDE the globe, what kinds of intraocular problems present as emergencies, and what signs are seen if a horse has a problem inside the eye?

  • Uveitis-ERU: Caution—screen carefully for stromal abscess
  • Glaucoma and bullous keratopathy

13. Some equine eye emergencies threaten sight and may require days or weeks of intense treatment. Can you discuss a few clinical skills or procedures that equine DVMs should master to make home treatment as simple and safe as possible?

  • Subconjunctival injection
  • Corneal cytology—sampling and interpretation
  • subpalpebral lavage system (SPL)  installation and maintenance
  • Eyelid repair techniques

14. It sounds like many equine eye emergencies can be handled on the farm, but can you tell us something about problems that are best handled by referral to a tertiary care center?

  • Any serious infection where farm/owner/RDVM does not have resources/experience to treat intensively
  • Melting ulcers
  • Ruptured globe/penetrating injury
  • Orbital fracture

15. What options are available if a veterinarian wants to get more information or training on equine ocular problems?

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EquiManagement’s Disease Du Jour
podcast is focused on equine research
and current best practices. Disease Du Jour
is brought to you in 2021 by Merck Animal Health.

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