Horses take removal of an eye in their stride, research shows

Horses seem to cope well with removal of an eye, the findings of research suggest.
Horses seem to cope well with removal of an eye, the findings of research suggest.

Removal of a horse’s eye can be distressing for owners who fear the animal may not be able to cope, but fresh research shows that a remarkably high number return to their previous work.

Horses, it would seem, literally take the setback in their stride, with a study in the Netherlands involving around 100 horses showing that 98 percent successfully returned to their previous work.

The findings of the research, which examined several important issues around eye removal, have been published in the journal BMC Veterinary Research.

The researchers found that removing a horse’s eye in a standing procedure and using an implant are both risk factors for post-operative site infections.

A horse several months after eye removal with the use of an implant, showing an excellent cosmetic appearance. Photo: Huppes et al DOI: 10.1186/s12917-017-1069-5
A horse several months after eye removal with the use of an implant, showing an excellent cosmetic appearance. Photo: Huppes et al DOI: 10.1186/s12917-017-1069-5

Implants are often used to improve the cosmetic appearance of horses after removal of an eye, which is known as enucleation. When a surgical site infection occurs, the implant will almost always be lost.

The study team from the Department of Equine Sciences within the Faculty of Veterinary Medicine at Utrecht University set out to collect data on the risk factors for surgical site infections after eye removal and to report long-term cosmetic results and whether the horses returned to work.

Their research focused on what is known as transpalpebral enucleation, a technique in which an incision is made around the eyelids, and the globe and all secretory tissues are removed within the conjunctival sac.

Records of horses undergoing this common form of eye removal between 2007–2014 at Utrecht University’s Equine Clinic were assessed and telephone interviews were used to obtain long term follow-up information.

Tsjester Huppes, Hanneke Hermans and Jos Ensink evaluated 107 eye removals. They grouped them three ways: Group 1 was clean and included the likes of equine recurrent uveitis and tumours inside the eye; Group 2 was non-clean and included eye injuries and infected ulcers. Group 3 comprised localised tumours around the eye that necessitated removal of the eye.

The study team found that implants were used in 49 of the horses.

The overall number of surgical site infections was eight, amounting to 7.5% of the surgeries assessed.

Their analysis showed that implants and standing procedures were significantly associated with the percentage of surgical site infections and increased the risk of them developing. They noted, however, that the number of standing eye removals were small – there were 11 included in the study – so no firm conclusions could be drawn.

“The eyes of horses in Groups 2 and 3 trended towards a larger risk for developing surgical site infections,” they reported.

“Prolonged use of antimicrobials, long surgery times and the opening of the conjunctival sac during dissection did not show significant associations with surgical site infection risk.

“The risk of surgical site infection after enucleation is low in clean eyes and when no implant is used,” they concluded.

“Although implants can be used for eyes that fall into Groups 2 and 3, 17% of the horses in these two groups developed a surgical site infection leading to loss of the implant.”

“Owners,” they said, “should be informed about these risks so that they can make an informed decision about the choice of technique.

“If owners prioritize quick, uncomplicated healing above the final cosmetic outcome, an implant should not be placed. If final cosmetic outcome with implant placement is important to the owner, then an enucleation [eye removal] under general anaesthesia may be preferable.”

Trevor Breen's Adventure De Kannan is to be officially retired at Hickstead next month.
Showjumper Adventure De Kannan won several major events after his right eye was removed in 2013, including the 2014 Hickstead Derby. The gelding had an eye condition which progressively worsened, to the point it was decided that he would be more comfortable having it removed. He is being retired from competition later this month. © Samantha Lamb

The study team acknowledged that placing a silicone implant during enucleation was a simple and affordable technique to improve the cosmetic result and a high owner satisfaction about the final appearance was achieved.

Long term follow-up on the final cosmetic appearance of the implant was obtained for 40 horses. Thirty-eight (95%) of the owners reported excellent to good cosmetic results. Two owners (5%) reported a poor cosmetic outcome.

Overall, 97.5% (39/40) of the owners reported that in a similar case they would again opt for an implant.

Long term follow-up information about pre- and post-operative use of 95 horses was available for evaluation, the results showing that nearly all of them  – 98% – returned to their previous work. Just two – a harness sport horse and a pleasure horse – did not return to their previous work.

A detailed breakdown is given in the table below.

Follow-up inquiries revealed that nearly all the horses involved in the restrospective study returned to their previous work. Table: Huppes et al DOI: 10.1186/s12917-017-1069-5
Follow-up inquiries revealed that nearly all the horses involved in the restrospective study returned to their previous work. Table: Huppes et al DOI: 10.1186/s12917-017-1069-5

A retrospective analysis of the risk factors for surgical site infections and long-term follow-up after transpalpebral enucleation in horses
Tsjester Huppes, Hanneke Hermans and Jos M. Ensink
BMC Veterinary Research 2017 13:155 DOI: 10.1186/s12917-017-1069-5

The study, published under a Creative Commons License, can be read here

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