2023 journal article

Solving an eye condition by looking to the rear

Equine Veterinary Education.

By: B. Gilger n‚ÄČ

Source: ORCID
Added: March 14, 2023

It is rare to read a modern scientific publication that describes a surgical technique used on human anal haemorrhoids for the management of an ocular disorder in a horse, but Bessonnat et al. (2023) describe the use of ligation, as described for haemorrhoids, for the treatment of recurrent ocular exuberant granulation tissue in a pony that was unresponsive to traditional therapies. Exuberant granulation tissue is an uncommon complication after corneal surgery in horses and usually develops at the harvest site of the conjunctival graft in the bulbar conjunctiva. As thoroughly described by the authors, exuberant granulation tissue in horses generally responds well to topical or local injection of corticosteroids, with or without tissue resection. In the pony described in this case report, the granulation tissue originally developed after a conjunctival graft surgery (Gunderson flap) was performed for the management of presumed endothelial immune-mediated keratitis. The granulation tissue was large, exuberant, and recurred twice despite standard-of-care therapy (i.e. use of topical and local steroid injection and resection using electrosurgical cauterisation). Following the two recurrences, the authors elected to use a ligature tape applied to the base of the pedunculated granulation tissue, as described for the treatment of severe haemorrhoids in humans. Following the ligation, the pedunculated granulation tissue turned reddish-black and spontaneously detached within 24 h after the ligation procedure. Following this technique, the eye recovered uneventfully and the granulation tissue did not recur during the 33-month follow-up period. The authors are applauded for their outside-of-the-box approach to effectively treat this case, despite venturing for inspiration to an anatomic location of the body whose surgical techniques are not commonly translated to the treatment of diseases of the eye. Recurrent periocular masses are common in horses, but these lesions are generally neoplastic. Periocular squamous cell carcinoma is a common example. Therefore, it is important that any mass removed from a horse's eye be examined histologically to definitively determine the underlying cause, if possible. The surgeon must differentiate granulation tissue from squamous cell carcinoma, lymphoma, and parasitic granulomas, among other causes. Most non-responsive or recurrent masses are simply the result of a misdiagnosis of the lesion and subsequent inappropriate treatment of the underlying cause(s). Specific and aggressive adjunctive therapy is needed to manage periocular neoplasia for example, and ligation or resection alone will result in the recurrence of the mass in greater than 50% of the cases, depending on the specific underlying neoplasia. Further work is needed to determine the frequency of occurrence of exuberant granulation tissue after ocular surgery in the horse, in comparison to neoplasia, but in my experience, the development of granulation is relatively uncommon and generally responds well to steroidal therapy. Prevention of granulation tissue around the eye after surgery can usually be accomplished by complete closure of the conjunctiva during surgery. It is common to not close the conjunctiva at the harvest site during surgery when surgeons are trying to reduce overall anaesthesia time, but doing so will minimise the development of granulation tissue. Furthermore, minimising the use of topical irritating substances, such as 5% sodium chloride or topical lidocaine, or procedures, such as a sub-palpebral lavage catheter, may also reduce the development of conjunctival granulation tissue. Finally, the use of small-sized sutures will minimise knot size and reduce conjunctival irritation (and thus the frequency of developing granulation tissue), especially when using braided absorbable sutures. Further studies are needed to determine the causes and prevention of granulation tissue in the horses' eyes. This case report also demonstrates the need for careful and thorough communication with the horse owner prior to surgery. Discussing the pros and cons of a salvage procedure such as Gunderson flaps are needed when managing chronic ocular diseases in horses such as endothelial immune-mediated keratitis. The described goal of the Gunderson flap procedure in the horse of this case report was to improve corneal oedema and vision and to prevent the development of corneal ulceration. Excessive corneal oedema from lack of corneal endothelial cell function results in the development of epithelial bullae. Fluid-filled bullae are easily ruptured by the horse leading to corneal ulceration, exposure of corneal nerve endings, and ocular discomfort. Although there was limited clinical description provided in the case report, no ocular discomfort was described in the horse (and pre-operative images were not provided). However, the horse required repeated procedures to manage the complications after surgery. The post-operative images (see figure 1a in the article) indicate a limited resolution to the corneal opacity but if the Gunderson flap helped prevent the development of corneal ulceration (which is not described for the 33 months after surgery), then this procedure likely prevented ocular discomfort despite the need for repeated surgeries to manage the granulation tissue that developed. Again, thorough client communication is needed prior to surgery to discuss these possible complications, such as the development of granulation tissue, and the possible need for further procedures if they develop. This case report effectively describes an uncommon corneal surgical complication in horses, the development of exuberant granulation tissue, the histologic diagnosis, appropriate therapy and an interesting, if unconventional, method to manage a rare case of unresponsive, recurrent granulation tissue of a pony's eye. This case report accentuates the need for histologic confirmation on masses removed from a horse's eye and the need for thorough communications with the owner prior to surgery to discuss the pros, cons and possible complications of ocular salvage procedures in the horse. No conflicts of interest have been declared.