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Management of a nonhealing, superficial corneal ulcer in a hyacinth macaw (anodorhynchus hyacinthinus).

Abstract: A 26-year-old, female hyacinth macaw (Anodorhynchus hyacinthinus) was presented for ophthalmology consultation for a history of a chronic, nonhealing corneal ulcer of the right eye. On examination, a 5 X 4-rnm axial, superficial corneal ulcer with loose epithelial edges was found. During multiple recheck examinations over 4 months, the ulcer was treated by debridement with a sterile cotton-tipped applicator, diamond burr debridement, diamond burr debridement with cyanoacrylate tissue adhesive, and grid keratotomy with cyanoacrylate tissue adhesive, all performed under anesthesia with eventual resolution of the corneal ulcer.

Key words: nonhealing corneal ulcer, keratotomy, debridement, cyanoacrylate tissue adhesive, avian, hyacinth macaw, Anodorhynchus hyacinthinus

Clinical Report

A 26-year-old, female hyacinth macaw (Anodorhynchus hyacinthinus) from the Oklahoma City Zoo (Oklahoma City, OK, USA) was presented for ophthalmologic examination after a 5-week history of a nonhealing corneal ulcer of the right eye. The bird weighed 1.24 kg and was otherwise healthy. The left eye was phthisical and blind from a previous traumatic injury as a juvenile. On ophthalmic examination, a central corneal opacity, mild bulbar conjunctival hyperemia, and no obvious blepharospasm were apparent. On slitlamp biomicroscopy, a 5 X 4-mm, axial, superficial corneal ulcer with loose epithelial edges was found (Fig 1). A few superficial corneal blood vessels were observed dorsotemporal to the lesion, extending into the cornea a distance of 2-3 mm from the limbus, and 3 focal, subepithelial, pinpoint, yellow opacities were identified in the ventral extent of the corneal lesion. No intraocular inflammation was observed, and the rest of the anterior ophthalmic examination was considered normal. Indirect ophthalmoscopy was not possible because of the location of the corneal lesion.

After applying topical anesthetic (proparacaine hydrochloride) to the right eye, a corneal swab was taken for aerobic culture and sensitivity testing as well as a sample prepared for corneal cytology. After corneal cleansing with dilute povidoneiodine, cotton-tipped applicator debridement was performed. After debridement, the ulcer measured 7 X 6-mm, but no deepening of the corneal lesion was observed because there was no stromal loss. Topical therapy of triple-antibiotic (neomycin, polymyxin B sulfates, and gramicidin) ophthalmic solution was administered q 6-8 h along with meloxicam (0.5 mg/kg SC once, then 0.5 mg/kg PO q24h) systemically for pain. Ceftiofur crystalline free acid (10 mg/kg SC q5d) had been administered as part of the initial empirical management and was continued after this examination. Results of the corneal cytologic examination showed a mild inflammatory reaction and few red blood cells, but no infectious organisms were identified. Aerobic bacterial culture results failed to yield growth of organisms, and systemic antibiotics were discontinued.

At 2 weeks, the patient was reexamined and found to still have the corneal ulcer present with loose epithelial edges, and no changes to the anterior portion of the eye had occurred. The corneal vascularization was unchanged, but the previous yellow foci in the ventral corneal ulcer had resolved. Mild weight loss was noted, and a blood sample was collected for a complete blood cell count and plasma biochemical analysis; results of which showed no significant findings. Because of the lack of corneal healing, the bird was anesthetized with isoflurane in oxygen administered by face mask, and the cornea was prepared as described previously. A fine-wire eyelid speculum was placed to prevent movement of the third eyelid and to assist visualization. A diamond burr equipped with a 2.5-mm, round, fine-grit tip (Algerbrush II, Alger Company Inc, New York, NY, USA) was used to debride the ulcerated corneal surface. The burr roughened the surface visibly, but was not noted to deepen the corneal lesion. Postoperative medical therapy remained the same with topical antibiotic and analgesic medications. Weight loss was attributed to hospitalization, with frequent treatment contributing to decreased food intake, so supplemental feedings were added.

At 7 weeks, the patient was reexamined and found to have a smaller, superficial corneal ulcer (4 X 3 mm), and the edges were not noted to be loose. Because of the improvement but lack of complete healing, the diamond burr procedure was repeated as before in all aspects. After diamond burr debridement, a fine layer of cyanoacrylate (3M vetbond, 3M Animal Care Products, St Paul, MN, USA) was applied to the ulcer bed by very careful application through a 25-gauge needle (Fig 2). Before drying, the glue was smoothed with the long shaft of the needle. Caution was taken to avoid overapplication or contact with the eyelids or nictitating membrane. Recovery and postoperative care was similar to previous procedures, with the addition of butorphanol tartrate (1 mg/kg IM q12h, for 1 day) to the analgesic protocol. Pain was monitored closely after cyanoacrylate application, and although mild discomfort was managed, no overt signs of intolerance were encountered.

The patient was reexamined after the cyanoacrylate sloughed 6 weeks later, at approximately 13 weeks. The corneal ulcer was still present and had not changed in size or appearance. Recheck blood test results showed no significant changes, and weight had returned to within reference intervals for this bird. The patient was again placed under anesthesia, and the cornea was prepped for debridement. Debridement was performed with sterile, cotton-tipped applicators with minimal increase in the size of the ulcer bed. A 27-gauge hypodermic needle was then used to perform a grid keratotomy under surgical magnification, taking great care to monitor each needle pass for depth because of the relatively thin appearance of the cornea during slit-lamp examination. A thin layer of cyanoacrylate was applied and allowed to dry as before. Topical and systemic therapy was administered as before. Recheck of the corneal ulcer at 18 weeks revealed an axial corneal scar with fine, superficial corneal blood vessels. No fluorescein stain uptake was observed at this time, and the ulcer was considered resolved (Fig 3).

Discussion

This report describes the diagnosis, management, and ultimate resolution of a nonhealing, superficial corneal ulcer in a hyacinth macaw. The management of this case was complicated, and reports of management of complicated ulcers in avian species are lacking. In this case, preservation of the one functional eye was important because of contralateral blindness. Preservation of the eye in psittacine species may be important in pet or exhibit species for aesthetic purposes but also for navigation of the environment and to minimize stress during adaptation to changing environments. This case incorporated techniques commonly used in the management of nonhealing corneal ulcers in domestic animals but not described in avian species.

There is a paucity of case reports describing superficial nonhealing ulcers in avian patients, with only 2 reports to date. A laughing kookaburra' (.Dacelo novaeguineae) was treated for a nonhealing, superficial corneal ulcer by debridement with a cotton-tipped applicator, and a peregrine falcon (Falco peregrinus)' was treated for bilateral, nonhealing ulcers with 360[degrees] conjunctival flaps. Other common surgical therapies and corneal-bandaging techniques used to treat nonhealing ulcers in domestic animals have not been described in avian species.

Nonhealing superficial corneal ulcers are well described in domestic dogs and have also been reported in cats, horses, and rabbits. (3,4) There are many potential causes for a nonhealing corneal ulcer in any species. Causes may include lid deformities, foreign bodies, abnormal hairs, lagophthalmos, abnormal tear film, and infection (bacterial, fungal, or viral), among others. The underlying pathophysiology of most nonhealing ulcers varies by species. In cats, development is commonly associated with feline herpesvirus, and brachycephalic cats are predisposed. (3,5) In horses, ulcers are often associated with corneal fungal infection, and there is a trend toward older-aged horses. (3,6) In dogs, nonhealing epithelial ulcers are found more frequently in middle-aged to older animals, and the underlying cause is often not easily discernible. Terms used for these noninfected canine ulcers have included indolent ulcers, canine recurrent ulcers, refractory ulcers, persistent corneal erosions, boxer ulcers, and spontaneous chronic corneal epithelial defects (SCCEDs). There is no sex prevalence in dogs, cats, or horses. (6)

Spontaneous chronic corneal epithelial defects in people are associated with basement membrane dystrophy, whereas in dogs, stromal alterations likely have a crucial role in the disease, causing a failed union between the epithelial basement membrane and the anterior layers of the corneal stroma. (3,4,7) In dogs, SCCED is well described, and although similar diseases occur in cats and horses, the abnormality is not well characterized. In the horse, one set of histologic characteristics does not definitively define this syndrome. The acellular hyaline zone commonly cited in canine SCCED is not a consistent finding in equine corneas. (8) The pathophysiology of nonhealing corneal ulcers in birds is not known.

The clinical appearance, however, is conserved across species, and diagnosis is based on this characteristic appearance. These lesions are characterized as superficial ulcerations with a nonadherent lip of corneal epithelium at the ulcer perimeter, with no stromal involvement. (3,9) The nonadherent perimeter causes a distinctive halo fluorescein staining pattern.

Once persistent mechanical and infectious causes for the nonhealing ulcer have been ruled, out, standard treatment of nonhealing ulcers in dogs includes debridement, diamond burr keratotomy, grid keratotomy, and corneal bandaging techniques among other therapies not used in this case. Commonly, first-line therapy begins with debridement with sterile cotton-tipped applicators because this method alone has a moderate resolution rate and little to no reported complications. (10)

Debridement with a diamond burr is another minimally invasive form of debridement with a higher healing rate and shorter healing time. (11) This technique has been studied in dogs and horses, may be safer than needle stromal puncture, and produces no scar. (11,12) In one study in dogs, (12) diamond burr debridement was evaluated in conjunction with placement of a contact lens. Results showed 93% of cases healed within 19 days, with no cases requiring further surgical intervention. The exact mechanism in which burr debridement influences healing is unknown. (12)

If further therapy after initial debridement of a nonhealing ulcer is needed, grid keratotomy can be performed. (3) Recommendations for grid keratotomy vary by species. This technique has been used to successfully treat nonhealing ulcers in dogs, horses, and a llama. (6,10,13) In one study, (10) 87% of dogs healed after one treatment with a median healing time of 7 days. Although commonly successful in dogs, this therapy is contraindicated in cats, where it frequently causes corneal sequestrum. (3)

Corneal bandaging can be used as an alternative to, or in conjunction with, surgical treatment. A contact lens can provide greater protection of the healing cornea and may increase surface tension with a mild suction effect, enhancing epithelial adhesion. (3) Application of a contact lens has been shown to improve healing rate and duration when used in conjunction with surgical treatment. (12) Cyanoacrylate glue is another corneal bandaging option that provides mechanical support for a weakened cornea when underlying stoma and epithelium are healing. (14) Glue can also provide a barrier against granulocyte degranulation, minimizing enzymatic tissue destruction and, when used early, can prevent keratomalacia. (14) The dried glue may cause mild discomfort for several days after application because of a foreign-body sensation on the eyelids, but its presence is speculated to diminish pain and ciliary spasm associated with ulceration by covering exposed nerve endings. (15) Application of cyanoacrylate glue requires anesthesia to avoid gluing adnexal structures.

In the case we describe, initial examinations ruled out mechanical and infectious causes. The bird was responsive to corneal stimulation, even under anesthesia, indicating intact corneal sensation; therefore, neurotrophic keratitis was considered less likely. The adnexal structures were normal, and no foreign bodies were present. Although considered unlikely given the lack of ophthalmic and systemic signs as well as known exposure history, viral causes for the corneal ulceration and delayed healing were not investigated and could have had a role in this case. The least-invasive treatments were chosen initially, and in the absence of evidence for any source of ongoing trauma, treatments were escalated as indicated by poor healing response. The contralateral eye in this patient was phthisical from a historical injury, and the animal was not sighted in that eye. Techniques causing temporary blindness in the affected eye (tarsorrhaphy or grafts) or those with high probability to cause vision-reducing scarring were avoided to preserve the functional eye of this patient Although data are lacking on the thickness of the macaw cornea, the corneal thickness of this patient appeared thin subjectively. Avian corneas in general have been found to be thinner than those of dogs and cats; therefore, keratotomy procedures were performed cautiously because complications of these techniques are unknown in avian patients. (16,17) Although all of these therapies can be applied to domestic animals under restraint with the application of topical anesthetic, they were performed in this patient under anesthesia because of potential corneal perforation of the thin cornea and to avoid the avian nictitating membrane, which is highly mobile because of striated muscle. Application of a soft contact lens was attempted, but the smallest available lens was too large for the cornea of this patient; therefore, cyanoacrylate glue was applied to protect the lesion. Mild discomfort was observed in this patient for a few days after each application and was managed with nonsteroidal anti-inflammatory therapy. Other treatments with fewer reported complications and species variance were attempted first, but because of the persistence of this lesion, grid keratotomy was ultimately performed. This series of treatments was found to be safe and effective for management of a nonhealing, superficial corneal ulcer in a hyacinth macaw.

Acknowledgments: We thank the veterinary technicians and animal care staff for their patience and dedication during the recovery of this bird.

References

(1.) Sabater M, Perez M. Management of a unilateral non-healing corneal ulcer and uveitis in a laughing kookaburra (Dacelo novaeguineae). Vet Ree Case Rep. 2014;2(1): 1-4.

(2.) Park FJ, Gill JH. Treatment of bilateral corneal ulceration in a peregrine falcon (Falco peregrinus) using 360 degree conjunctival flaps. Aust Vet J. 2005;83(9):547-549.

(3.) Maggs DJ. Cornea and sclera. In: Maggs DJ, Miller PE, Ofri R, eds. Slatter's Fundamentals of Veterinary Ophthalmology. 4th ed. St Louis, MO: Saunders Elsevier; 2008:175-202.

(4.) Bentley E, Abrams GA, Covitz D, et al. Morphology and immunohistochemistry of spontaneous chronic corneal epithelial defects in dogs. Invest Ophthalmol Vis Sei. 2001;42(10):2262-2269.

(5.) La Croix NC, van der Woerdt A, Olivero DK. Nonhealing corneal ulcers in cats: 29 cases (1991-1999). J Am Vet Med Assoc. 2001;218(5):733-735.

(6.) Michau TM, Schwabenton B, Davidson MG, Gilger BC. Superficial, nonhealing corneal ulcers in horses: 23 cases (1989-2003). Vet Ophthalmol. 2003;6(4):291-297.

(7.) Ledbetter EC, Gilder BC. Diseases and surgery of the canine cornea and sclera. In: Gelatt KN, Gilger BC, Kern TJ, eds. Veterinary Ophthalmology. 5th ed. Ames, 1A: Wiley-Blackwell; 2013:976-1049.

(8.) Hempstead JE, Clode AB, Borst LB, Gilger BC. Histopathological features of equine superficial, nonhealing, corneal ulcers. Vet Ophthalmol. 2014; 17(suppl f):46-52.

(9.) Moore PA. Diagnosis and management of chronic corneal epithelial defects (indolent corneal ulcerations). Clin Tech Small Anim Pract. 2003; 18(3): 168-177.

(10.) Stanley RG, Hardman C, Johnson BW. Results of grid keratotomy, superficial keratectomy, and debridement for the management of persistent corneal erosions in 92 dogs. Vet Ophthalmol. 1998;1(4):233-238.

(11.) Lassaline-Utter M, Cutler TJ, Michau TM, Nunnery CM. Treatment of nonhealing corneal ulcers in 60 horses with diamond burr debridement (2010-2013). Vet Ophthalmol. 2014; 17(suppl 1):76-81.

(12.) Gosling AA, Labelle AL, Breaux CB. Management of spontaneous chronic corneal epithelial defects (SCCEDs) in dogs with diamond burr debridement and placement of a bandage contact lens. Vet Ophthalmol. 2013; 16(2):83-88

(13.) Jones ML. Gilmour MA, Streeter RN. Use of grid keratotomy for the treatment of indolent corneal ulcer in a llama. Can Vet J 2007;48(4):416-419.

(14.) Watte CM, Elks R, Moore DL, McLellan GJ. Clinical experience with butyl-2-cyanoacrylate adhesive in the management of canine and feline corneal disease. Vet Ophthalmol. 2004;7(5):319-326.

(15.) Bromberg NM. Cyanoacrylate tissue adhesive for treatment of refractory corneal ulceration. Vet Ophthalmol. 2002;5(1):55-60.

(16.) Jones MP, Pierce KE, Ward D. Avian vision: a review of form and function with special consideration to birds of prey. J Exot Pet Med. 2007:16(2): 69-87.

(17.) Montiani-Ferreira F, Cardoso F, Petersen-Jones S. Post natal development of central corneal thickness in chicks of Gallus gallus domesticus. Vet Ophthalmol. 2004;7(1):37-39.

Lynnette Waugh, DVM, Jonathan Pucket, DVM, MS, Dipl ACVO, Gretchen A. Cole, DVM, Dipl ACZM, Dipl ECZM (ZHM), and Jennifer D'Agostino, DVM, Dipl ACZM

From the Oklahoma City Zoo, 2101 NE 50th St. Oklahoma City, OK 73111, USA (Waugh, Cole, D'Agostino); and the Department of Veterinary Clinical Sciences, Oklahoma State University. Stillwater. OK. 74078, USA (Pucket)

Caption: Figure 1. Nonhealing corneal ulcer in the right eye of a hyacinth macaw. Fluorescein stain uptake highlights a 5 X 4-mm, axial, superficial corneal ulcer with loose epithelial edges.

Caption: Figure 2. Cyanoacrylate glue in place over a nonhealing corneal ulcer in a hyacinth macaw after diamond burr debridement at seven weeks.

Caption: Figure 3. The right eye of a hyacinth macaw with no fluorescein stain uptake, indicating resolution of the corneal ulcer at 18 weeks.
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Title Annotation:Clinical Report
Author:Waugh, Lynnette; Pucket, Jonathan; Cole, Gretchen A.; D'Agostino, Jennifer
Publication:Journal of Avian Medicine and Surgery
Date:Sep 1, 2017
Words:2852
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