Eye Trouble: Infection Risk After Equine Transpalpebral Enucleation

In a retrospective study recently published in BMC Veterinary Research, Dutch researchers determined that surgical site infection (SSI) risk after equine transpalpebral enucleation significantly increases with orbital implant placement and standing surgical position.

Transpalpebral enucleation is a common surgery for eyes that are either painful and nonvisual or visual with a poor prognosis. Unfortunately, even with proper surgical technique, preventing SSIs can be challenging because of several surgical factors, including conjunctival sac leakage and dead space following eye removal.

Orbital implants help improve cosmetic appearance after an enucleation. However, previous studies have reported an increased SSI risk with orbital implants. If a horse with an orbital implant develops an SSI, the implant must be removed.

Study Design

Researchers sought to identify SSI risk factors and obtain owner assessments on cosmetic appearance and return to work following equine transpalpebral enucleation. For 107 horses receiving a standard transpalpebral enucleation, medical records were reviewed for the following information:

• Which eye was removed
• Indication for enucleation
• Orbital implant placement
• Surgical position: standing or lateral recumbency
• Surgical details: conjunctival sac opening, surgery duration
• Postsurgical details: antimicrobial usage

Horses were grouped according to surgical indication:

• Group 1: Clean eyes, n = 58
• Group 2: Nonclean eyes, n = 31
• Group 3: Ocular tumor, n = 18

Criteria from the Centers for Disease Control and Prevention (CDC) were used to define an SSI—onset within 30 days without an implant or within 1 year with an implant.

Follow-up information from owners on cosmetic appearance and return to work was obtained via evaluation forms and telephone interviews.

Results and Discussion

Demographics

Forty-nine horses received an orbital implant, with group 1 horses receiving the highest number of implants (n = 37). The authors noted that owners were informed about orbital implants before surgery, with recommendations against implants if cancer or infection was present.

Nearly all horses were placed in lateral recumbency and received short-term antibiotic treatment (24 hours); several horses received long-term antibiotic treatment (>24 hours) for reasons including conjunctival sac perforation during surgery and postoperative swelling.

Infections

Eight infections were classified as SSIs. Two infections occurred several years after surgery and thus were not classified as SSIs.

Using univariable regression analysis, the researchers observed several nonsignificant increases in SSI risk. For example, SSIs were 4 times more likely with long-term antibiotics than with short-term antibiotics. An opened conjunctival sac only minimally increased SSI risk, suggesting the importance of perioperative antibiotic prophylaxis.

Multivariable regression analysis revealed that orbital implant use and standing position significantly increased SSI risk. “Nonclean” and “tumor” indications demonstrated a nonsignificant trend toward increased SSI risk. Notably, 17% of horses in groups 2 and 3 that received implants developed an SSI, highlighting the risk associated with orbital implants when ocular infection or cancer is present.

Follow-up Information

Cosmetic appearance data were obtained for 40 horses that received an implant. Nearly all owners rated the cosmetic appearance as “excellent” or “good.” The authors stated that “achieving owner satisfaction about the cosmetic results is the most important goal in cosmetic procedures.” However, given the increased SSI risk with implant use, the authors advised allowing owners to decide whether cosmetic appearance is important.

Return to work data were available for 95 horses, 9 of which were already retired at the time of surgery. Of the 86 working horses, 84 returned to work after enucleation. Two horses did not return to work because monocular vision affected their behavior.

Overall, given the study’s results, the authors advised providing horse owners with information about SSI risk factors associated with transpalpebral enucleation.

Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.