December 2021

In this VETgirl online veterinary continuing education blog, Dr. Kathryn M. Slaughter-Mehfoud, DVM, MPH, Equine Surgeon at Bannon Woods Veterinary Hospital, reviews how to do an enucleation in a horse in the field.

By Dr. Kathryn M. Slaughter-Mehfoud, DVM, MPH, Equine Surgeon

How to do an Equine Enucleation in Field

Enucleation is the most commonly performed ophthalmic surgery in horses. Enucleation involves surgically removing the globe, nictitans, palpebral membranes, and the conjunctiva. This surgical procedure is performed for non-healing corneal ulcers, intraocular infections, ocular trauma, intraocular neoplasia, recurrent uveitis, and intraocular trauma. Some equine practitioners are comfortable performing this procedure in the field under standing sedation. However, many equine practitioners refer because they’re uncomfortable performing enucleations in the field. I’ve heard many veterinarians recount stories of intraoperative complications while the horse was under standing sedation. From the lengthy pre-operative regional anesthesia, the horse shaking its head suddenly and erratically, intraoperative hemorrhage, and having to add more local anesthetic throughout the procedure, standing enucleation can be daunting to veterinarians. Given the appropriate conditions, enucleation is a simple surgical procedure and is reasonably performed in 15 minutes. Similar to castrations performed in the field, below I describe enucleation performed under general anesthesia in the field.

Pre-operative sedation includes an alpha-2 agonist and an opioid, followed by induction with ketamine and a muscle relaxant, such as diazepam. Use sound judgement when estimating weights and calculating the drug dosages. You likely won’t be able to provide additional doses of medications during enucleation, and an anesthetically light horse can turn this simple surgical procedure into a dangerous situation. For surgical preparation, I strongly recommend dilute betadine solution. It’s extremely easy for the contralateral eye to receive splashes of the sterile preparation, and we certainly don’t want the only remaining eye to get a corneal ulcer. Following your preparation, a small drape with a small opening is appropriate for the eye being enucleated.


There are two surgical techniques for enucleation, transpalpebral and subconjunctival. I recommend using the transpalpebral technique because it removes the globe, conjunctiva, and nictitating membrane in one mass. This enucleation technique protects the orbit from contamination of a globe with intraocular neoplasia or infection. The technique described below is for transpalpebral enucleation.

Use two or three Backhaus towel clamps to oppose the eyelids. The towel clamps provide a great handle for surgical removal of the globe during dissection. Using a #15 or a #10 scalpel blade, make a full-thickness, elliptical incision circumferentially around the eye, approximately 5 mm from the eyelid margins. Metzenbaum or curved Mayo scissors are used for blunt and sharp dissection to separate the subcutaneous tissues from the globe. The medial and lateral canthal ligaments are extremely fibrous and require curved Mayo scissors for transection. Once the globe is freed from the subcutaneous tissues, blunt and sharp dissection of the extraocular muscles is continued circumferentially around the sclera using curved Mayo scissors. The orbital vasculature and the optic nerve are sharply transected using curved Mayo scissors and the globe is removed. At this step, 4×4 gauze may be packed in the orbit for hemostasis.

The subcutaneous layer is closed in a simple continuous pattern using size 0 absorbable suture material. If using 4×4 gauze for hemostasis during closure, make sure to remove all gauze before complete closure. The skin is closed in a simple continuous pattern using size 2-0 absorbable suture material. Following closure, a compression bandage is placed over the surgical site using gauze and elastikon. Recovery from field general anesthesia follows the same principles of routine field castrations. Enucleated patients were most likely non-visual prior to the procedure, thus, recovery from general anesthesia is often not problematic due to sudden vision loss.

For post-operative care, if the owner is able to appropriately bandage the horse, I recommend a pressure bandage be changed every 2-3 days for 10-14 days post-operatively. If the owner isn’t able to appropriately bandage the horse, I don’t recommend a pressure bandage because the risk of the only remaining eye receiving a corneal ulcer or other trauma due to a slipped bandage is concerning. Broad spectrum antimicrobials and anti-inflammatory medications are recommended for one week post-operatively.

Enucleation can be a simple, smooth surgical procedure performed in the field. Veterinarians perform at their best when the surgical situation is in their comfort zone. Castrations are performed routinely under general anesthesia in the field without complications. There is no shame in performing an enucleation under general anesthesia in the field setting. With enucleation under general anesthesia, not only is the surgical preparation especially quicker due to lack of regional anesthesia, but the surgical procedure is often much quicker because the horse doesn’t constantly move its head and require more local anesthesia.

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