Figure 1. Pint, a then-13-year-old male neutered Nova Scotia duck tolling retriever, with multiple eyelid melanocytic tumors in both eyes. Photo courtesy Mike Bannasch Pint was a “local celebrity,” having been the official kicking tee retriever for the Aggies football team until his retirement in 2022.1 The then-13-year-old male Nova Scotia duck tolling retriever was owned by Danika Bannasch, BS, PhD, DVM, a faculty member at University of California (UC) Davis, and her husband, Mike, who also works at UC Davis. Pint was enjoying his retirement when it was noted the dark nodules on both lower eyelids were growing in size and number. Nova Scotia duck tolling retrievers have been identified as a breed with higher rates of developing cutaneous melanocytic tumors.2 These tumors can be located on the eyelid margin and eventually become large or numerous enough to require surgical intervention. Melanocytic eyelid neoplasms are reported to typically be benign in behavior (melanocytoma), with Vizslas and Doberman pinchers also having a high incidence at this eyelid location.3,4 If the masses become large enough, they can contact the cornea and disrupt the tear film, which can irritate the eye. Traditional eyelid surgeries, such as cryotherapy or a full-thickness “wedge” excision, followed by primary closure, can treat these lesions if they are small (less than 1/3 of the eyelid margin is a generally accepted amount to excise for a “wedge” resection).4 However, despite surgery, they can still recur or develop in another location on the eyelid. Presentation When Pint presented with nearly the entirety of both lower eyelids and a small portion of the upper eyelids affected by pigmented tumors (Figure 1), extensive surgical intervention was not necessarily the first choice for treatment. Instead, photodynamic therapy (PDT) was considered. PDT has been reported for use in ophthalmic veterinary medicine for horses,5-7 cats,8 and cattle9 with ocular squamous cell carcinoma. No publications currently exist for its use with melanocytic tumors in veterinary patients; however, the dye’s anti-tumor properties,5 healing benefits,10 and lack of requirement to close the extensive surgery site with a rotational or advancement graft made it an appealing choice for Pint’s eyelids, to avoid a more invasive and lengthy surgery. Surgery Pint’s tumors on his lower eyelids were excised under heavy sedation and local anesthetic, removing the cutaneous (outer) aspect of his lower eyelids and the eyelid margin, but leaving the underlying tissues, including the conjunctiva at the deepest aspect, intact. This is done to provide “scaffolding” for the tissue to heal while preserving the physical functionality of the lower eyelid (Figure 2). Figure 2. Intraoperative photo of the left eye after surgical excision of the eyelid melanocytic tumors, leaving the underlying tissues to provide a ‘scaffolding’ for healing. This is before the infracyanine green application. Photo courtesy Dr. Lauren Charnock A photosensitizing dye (infracyanine green, one percent) was then applied to the surgery site via a combination of injections into the edge of the cut tissue and application to the surface of the surgical site. Once the site was saturated with the dye, an 810 nm diode laser was used to treat the surgical site to activate the dye. Various energy levels were used to treat the site and create an eschar on the surgery site (Figure 3). Topical antibiotics were applied to both eyes, and Pint was given anti-inflammatory pain medication to help manage inflammation after surgery. Figure 3. Immediate post-operative photos of the right eye (oculus dexter, OD) and left eye (oculus sinister, OS) after treatment and eschar development following laser treatment of the surgical site. The dark green appearance is due to the infracyanine green and laser therapy. Photo courtesy Dr. Lauren Charnock Outcome Within the first week following surgery, the eschar disintegrated from the surgery sites, revealing healthy tissue underneath (Figure 4). Over the next few weeks, Pint’s eyelids continued to heal (Figure 5). The excised eyelid tissue had been submitted to a veterinary pathologist, where benign melanocytic tumors were confirmed with incomplete margins. Given this finding, while the tumors were benign, there was a risk they could recur. Figure 4. One week following photodynamic therapy. The surgery sites are losing the eschar, revealing healthy tissue underneath. Photo courtesy UC Davis Ophthalmology Service Figure 5. The right (OD) and left (OS) eyes approximately one month following photodynamic therapy. The eschars have resolved, and the eyelid tissue has healed. There is no evidence of tumor regrowth. Photo courtesy UC Davis Ophthalmology Service Pint continued to be a much-loved member of the UC Davis community until his passing due to cancer unrelated to his eyelid tumors in May 2024, 11 months following his eyelid surgery.1 Recurrence of the eyelid tumors was not observed throughout this time (Figure 6). Figure 6. Pint, during his healing process, wears an Elizabethan collar to prevent him fromrubbing his face while the eschar disintegrates from the surgery site. Photo courtesy Mike Bannasch A closer look at PDT cases PDT has been described as having anti-tumor and anti-microbial properties and positive effects on tissue healing. While some mechanisms of action are not fully understood, it is accepted cancer cells’ preferential uptake of the photosensitizing agent and subsequent laser activation results in free radical formation, oxidative damage, damage to cell membranes, and ischemic injury to cancer cells, without risk of toxicity and minimization of damage to healthy adjacent tissue.5,8,10 In a case series of 10 equine eyes, PDT with verteporfin and a 665 nm diode laser successfully achieved a multi-year disease-free interval with only one case of recurrence.6 In a published abstract, where indocyanine green was used as the photosensitizing agent, a four percent recurrence rate (1/23 eyes) was observed in a population of horses with squamous cell carcinoma despite incomplete surgical margins being identified on histopathology in 13/23 cases.7 In two feline cases of eyelid squamous cell carcinoma with marginal surgical resection, adjunctive treatment with one percent infracyanine green resulted in a cosmetic and functional outcome with no evidence of tumor recurrence after treatment during the follow-up time (six months to one year) despite incomplete surgical margins in both cats.8 The procedure appeared to be well tolerated in all the described cases. Case summary Pint benefited from PDT for the treatment of his eyelid tumors by being able to avoid a more involved surgical procedure due to the tumors’ extensive eyelid involvement, and he was able to remain without eyelid tumor development for 11 months following his procedure despite incomplete tumor resection (Figure 7). Figure 7. Pint, fully healed, with no evidence of tumor regrowth, seven months followingphotodynamic therapy of the eyelids of both eyes. Photo courtesy Mike Bannasch Pint was the first canine patient to receive PDT at UC Davis for eyelid cancer due to his owners’ keen interest in the treatment and involvement with the UC Davis School of Veterinary Medicine. Subsequently, Pint’s case jumpstarted the use of PDT for this condition and other eye diseases in canine (and feline) patients at the university. While more complex and invasive surgical procedures may still be recommended in some patients, PDT may offer an alternative treatment, depending on the tumor type, tumor location, and the patient’s overall health. Lauren N. Charnock, DVM, MS, DACVO, earned her veterinary degree at the Western College of Veterinary Medicine, University of Saskatchewan, and completed a small animal rotating internship at the Atlantic Veterinary College, University of Prince Edward Island. She then completed a specialty internship and residency in comparative ophthalmology at Auburn University, where she received training in photodynamic therapy for various ocular conditions. Dr. Charnock is now an assistant professor of Clinical Veterinary Ophthalmology at the University of California (UC)-Davis. She may be reached at lncharnock@ucdavis.edu. References Hinds T, Warren R. Pint, UC Davis’ Beloved Wonder Dog, Passes Away. UC Davis Veterinary Medicine News and Events. 2024. July 15. https://www.vetmed.ucdavis.edu/news/pint-uc-davis-beloved-wonder-dog-passes-away Graf R, Pospischil A, Guscetti F, Meier D, Welle M, Dettwiler M. Cutaneous Tumors in Swiss Dogs: Retrospective Data From the Swiss Canine Cancer Registry, 2008–2013. Vet Pathol. 2018;55(6):809-820. Dubielzig RR, Ketring K, McLellan GJ, Albert DM. Diseases of the eyelids and conjunctiva. In: Veterinary Ocular Pathology. Elsevier; 2010:143-199. Wang AL, Kern T. Melanocytic Ophthalmic Neoplasms of the Domestic Veterinary Species: A Review. Top Companion Anim Med. 2015;30(4):148-157. Giuliano EA, Ota J, Tucker SA. Photodynamic therapy: basic principles and potential uses for the veterinary ophthalmologist. Vet Ophthalmol. 2007;10(6):337-343. doi:10.1111/j.1463-5224.2007.00578.x Giuliano EA, MacDonald I, McCaw DL, et al. Photodynamic therapy for the treatment of periocular squamous cell carcinoma in horses: a pilot study. Vet Ophthalmol. 2008;11(s1):27-34. Hefner E, McMullen Jr. RJ. Treatment of Equine Ocular and Periocular Squamous Cell carcinoma with Infracyanine Green Photodynamic Therapy. Abstracts: The 51st Annual Scientific Meeting of the American College of Veterinary Ophthalmologists, Virtual Conference, Sept 23–27, 2020. Vet Ophthalmol. 2020;23(6). Sebbag L, Pe’er O. Marginal resection and infracyanine green‐mediated photodynamic therapy in the management of feline eyelid squamous cell carcinoma: Two cases. Vet Ophthalmol. 2024;27(4):374-381. Ng ATJ, McMullen RJ, Shaw GC, Passler T, Stockler J. Limbal Squamous Cell Carcinoma in a Black Baldy Cow: Case Report and Surgical Treatment. Roccabianca P, ed. Case Rep Vet Med. 2023;2023:1-6. Ning X, He G, Zeng W, Xia Y. The photosensitizer-based therapies enhance the repairing of skin wounds. Front Med. 2022;9:915548.
