Histologic evaluation of the immediate effects of diamond burr debridement in experimental superficial corneal wounds in dogs

Purpose To evaluate the corneal changes immediately after diamond burr debridement of superficial corneal wounds in dogs. Spontaneous chronic corneal epithelial defects (SCCEDs) are the most common form of canine recurrent corneal ulcers. The diamond burr has been used in the management of corneal lesions in humans since 1983. Recently, it has been successfully used in the treatment of SCCEDs in dogs; however, little has been documented as to its mechanism of action. Methods Five adult female research dogs euthanized for reasons unrelated to the study were included, providing 10 normal eyes. An excimer laser spatula was used for epithelial removal after delineation with an 8 mm punch biopsy trephine. Diamond burr debridement was performed for 30 and 45 s in five eyes each (groups 1 and 2 respectively). The procedure was performed on the ventral half of the experimental defect as well as ventral normal cornea, immediately after euthanasia, and prior to enucleation. Samples were processed routinely for histologic evaluation and stained with periodic acid–Schiff. Results No stromal defects could be identified under light microscopy. In experimental corneal wounds, multi‐focal areas remained covered by the epithelial basement membrane (BM) after diamond burr treatment in both groups (group 1 = 48%±16SD, group 2 = 26%±12SD). Removal of BM on group 2 was significantly higher than group 1 (P < 0.05). Conclusions The diamond burr allows a safe method of debridement and does not create defects beyond the epithelial BM in corneal wounds in normal dogs. Evaluation of the diamond burr debridement in cases of SCCEDs is warranted.     

Thermal cautery of the cornea for treatment of spontaneous chronic corneal epithelial defects in dogs and horses

A thermal cautery technique was used to treat spontaneous chronic corneal epithelial defects (SCCEDs) in 9 eyes of 8 dogs and 2 eyes of 2 horses. Animals were sedated, and a topical anesthetic was applied. A handheld thermal cautery unit was then used to make multiple, small (< or = 1 mm in diameter), superficial burns throughout the affected area. The cautery unit was applied just until the slightest degree of contraction of the collagen fibrils was observed. After the stromal bed of the defect was treated, a rim of epithelium that extended approximately 1 mm around the denuded stroma was also subjected to thermal cautery. Following surgery, a contact lens was placed in dogs but not in horses, and the eye was treated with broad-spectrum antimicrobial ophthalmic solutions. Defects in all 11 eyes healed with minimal scarring; mean time to healing in dogs was 2.1 weeks (range, 2 to 3 weeks). The defect healed in 1 week in 1 horse and in 2 weeks in the other. Many therapeutic options are available for the treatment of SCCEDs. Procedures such as epithelial debridement and anterior stromal puncture have been shown to have a high rate of success. In cases for which these less invasive procedures fail, our results suggest that thermal cautery may be a reasonable alternative to previously described treatments for SCCEDs in dogs and horses prior to more invasive procedures such as superficial keratectomy.     

Diagnosis and management of chronic corneal epithelial defects (indolent corneal ulcerations)

Chronic corneal epithelial defects (CCEDs; indolent corneal ulcerations) are the most common refractory ulcerations in veterinary medicine and are diagnosed by their classic appearance. CCEDs are superficial ulcerations without stromal involvement and have a nonadherent epithelial border (lip). Fluorescein stain adheres to the exposed stroma and extends below the epithelial border, outlining the epithelial lip. CCEDs occur secondary to adnexal disease, keratoconjunctivitis sicca, exposure keratitis, neurotrophic keratitis, and primary corneal disease. In cats, herpes keratitis is associated with the development of CCEDs. Bacterial infections are not responsible for the refractory nature of CCEDs. Because of the refractory nature of CCEDs, treatment can be frustrating for both owner and veterinarian. Current treatment recommendations consist of identifying and treating the underlying cause and performing procedures that stimulate epithelialization and adhesion of the corneal epithelium. Initial treatment of CCEDs includes ulcer debridement and grid keratotomy. Superficial keratectomy is indicated in refractory cases.     

Efficacy of two chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects and ulcerative keratitis associated with bullous keratopathy in dogs

OBJECTIVE: To determine the efficacy of two antimicrobial-chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects (SCCED) and ulcerative keratitis associated with bullous keratopathy in dogs. ANIMALS STUDIED: Eighty dogs with SCCED and 14 dogs with ulcerative keratitis associated with bullous keratopathy. PROCEDURE: Following manual debridement of nonadherent epithelium, dogs were treated topically with a chondroitin sulfate ophthalmic solution containing either tobramycin or ciprofloxacin. Patients were re-evaluated at 2-week intervals for 4 weeks. RESULTS: After 2 weeks of treatment, 53.6% of eyes with SCCED and 17.6% of eyes with ulcerative keratitis associated with bullous keratopathy had healed. After 4 weeks of treatment, 81.0% of eyes with SCCED and 23.5% of eyes with ulcerative keratitis associated with bullous keratopathy had healed. There were no statistically significant differences in healing percentages between the tobramycin-chondroitin sulfate solution treatment groups and the ciprofloxacin-chondroitin sulfate solution treatment groups. Two dogs with SCCED, one treated with the tobramycin-chondroitin sulfate solution and the other treated with the ciprofloxacin-chondroitin sulfate solution, developed sterile corneal stromal abscesses during the study. CONCLUSIONS: Topical therapy with an antimicrobial-chondroitin sulfate ophthalmic solution combined with manual debridement of nonadherent epithelium compares favorably with other published medical and surgical therapies for SCCED; however, these compounds are only equivocally more effective than therapy with manual debridement alone. These solutions appear to be ineffective in the treatment of ulcerative keratitis associated with bullous keratopathy. The significance of the two cases of corneal stromal abscessation is unknown at this time and warrants further investigation.     

Effects of radiofrequency hyperthermia on the healthy canine cornea

Radiofrequency hyperthermia was used to induce axial corneal lesions in the eyes of 10 dogs. Clinical observations were continued for up to 6 months, using biomicroscopy and indirect ophthalmoscopy. Eyes were harvested at intervals for light and electron microscopic evaluation. Clinical alterations included immediate corneal opacification and epithelial disruption at the site of electrode contact. Ulcerative keratitis persisted for 4 to 6 days, accompanied by anterior uveitis. Additional corneal changes included stromal thinning, edema, and vascularization. Final evaluation revealed negligible alterations in corneal contour or clarity 6 months after treatment. Microscopically, epithelial and superficial stromal necrosis preceded epithelial loss. Stromal alterations included edema (associated with focal endothelial detachments), vascularization, and inflammatory cell infiltration. Recovery was characterized by keratocytic hyperplasia and hypertrophy, epithelial proliferation, and stromal condensation.     

Superficial stromal keratitis in the dog

Superficial stromal keratitis or pannus is a syndrome of corneal, conjunctival and third eyelid inflammation. Superficial stromal keratitis mainly presents as a subepithelial corneal infiltration of vascular connective tissue, and usually arises from the lateral (temporal) limbal area. In some dogs perilimbal hyperaemia and third eyelid blepharitis can be present without corneal involvement. The most commonly affected breed of dog is the German Shepherd. Most cases of superficial stromal keratitis can be controlled with topical corticosteroids, and only rarely is cryosurgery or superficial keratectomy required to remove excessive pigment and or granulation tissue. The precise aetiology of SSK is unknown, but is likely to be multifactorial, with sunlight being a significant factor. Corneal lipidosis and keratoconjunctivitis sicca can occur secondary to superficial stromal keratitis.     

Successful treatment of an unusually large corneal epithelial inclusion cyst using equine amniotic membrane in a dog

A 10‐year‐old intact male Yorkshire Terrier was referred for investigation of a large raised and nonpainful corneal lesion oculus dexter. Clinical examination revealed a pale, translucent corneal mass, which occupied half of the corneal surface and measured 11 mm × 11 mm × 13 mm. The mass was removed by superficial keratectomy and equine amniotic membrane (AM) was transplanted into the large corneal defect to cover the wound and provide tectonic support for the remaining cornea. The mass was histologically confirmed as a corneal epithelial inclusion cyst. There was no evidence of recurrence or complication at the surgical site 100 days postoperatively. Corneal epithelial inclusion cysts are uncommon in dogs. Although superficial keratectomy is the recommended treatment for corneal inclusion cyst, the combination of superficial keratectomy and AM transplantation had to be considered as an alternative for repair of large corneal defects. This is the first case report of the combined application of AM and superficial keratectomy to successfully treat a corneal inclusion cyst in a dog.     

Corneal epithelial disease.

This article reviews conditions that primarily affect the corneal epithelium as distinct from corneal stromal diseases. Corneal ulceration is discussed elsewhere in this issue. The other corneal conditions include a variety of more subtle epithelial disease,which might colloquially be termed epitheliopathies, as well as uninfected indolent superficial ulcerations, corneal neoplasia, and eosinophilic keratitis. The fungal plaque is an unusual and somewhat chronic form of epithelial infection. Although less common than corneal ulcers, this collection of lesions may present uniquely challenging obstacles to diagnosis and identification of a cure. Newer therapies and surgical strategies are discussed.     

Management of a persistent corneal erosion in a boxer dog

A dog was presented to the New York State College of Veterinary Medicine with a one-month history of corneal ulceration. The corneal lesion was diagnosed as a persistent corneal erosion (PCE) and treated initially with debridement and supported with a contact lens. One week later, the corneal erosion remained unepithelialized. Following debridement, multiple anterior stromal punctures were performed. Within 10 days, the erosion was healed as evidenced by coverage of the cornea with adherent, uninterrupted epithelium. The proposed etiology and management of PCE in dogs is discussed.     

Superficial, nonhealing corneal ulcers in horses: 23 cases (1989-2003)

Objective To characterize superficial, nonhealing corneal ulcers in the horse and to assess the affect of age, breed, sex, inciting cause of the ulcer, and treatment on healing time of these ulcers. Design Retrospective study. Animals Twenty‐three horses with superficial, nonhealing corneal ulcerations. Procedure Medical records from 1989 to 2003 of horses diagnosed with superficial, nonhealing corneal ulcers were reviewed. Signalment, duration of clinical signs, ophthalmic abnormalities, treatment and response to treatment were recorded. Horses were treated, in addition to medical therapy, using debridement, debridement and grid keratotomy, superficial keratectomy, and superficial keratectomy with conjunctival graft placement. Results Mean age ± SD of horses was 13.7 ± 5.8 years. The mean time of presence of the corneal ulceration was 38.9 ± 21.3 days. Mean time to complete re‐epithelialization of the corneal ulcers after treatment was 20 ± 14.7 days. Horses treated with debridement alone, grid keratotomy and superficial keratectomy healed in a mean time of 15.3 ± 14.6 days, 16 ± 12.6 days, and 22.8 ± 6.7 days, respectively. Conclusions and clinical relevance Horses treated with a single debridement at initial evaluation healed in a significantly shorter time period than horses treated with grid keratotomy or superficial keratectomy. The latter two procedures may be beneficial in the treatment of nonhealing ulceration in horses, but the results of this study suggest that these procedures should only be performed following failure of the ulcer to heal after epithelial debridement.     

Corneal anatomical differences in the aetiology of chronic superficial keratitis

The apparently normal corneas of 14 diseased eyes of German shepherd dogs (GSDs) were shown to possess very thin epithelial layers on microscopy. Normal corneas of 38 GSDs and 113 dogs of various breeds and crossbred animals were compared for epithelial thickness, structure of corneal stroma and corneal strength. Due to lower values for these criteria found in the GSDs they are considered to play an important role in the aetiology of chronic superficial keratitis.     

Nonhealing corneal ulcers in cats: 29 cases (1991-1999)

OBJECTIVE: To compare mean healing times after debridement, debridement with grid keratotomy, and superficial keratectomy in cats with nonhealing corneal ulcers. DESIGN: Retrospective study. ANIMALS: 29 cats with 36 nonhealing corneal ulcers. PROCEDURE: Medical records of cats with nonhealing corneal ulcers were reviewed. Signalment, duration of clinical signs, ophthalmic abnormalities, and response to various treatment protocols were recorded. RESULTS: Mean age of affected cats was 7 years, 8 months. Affected breeds included domestic shorthair (17 cats), Persian (9), Himalayan (2), and Siamese (1). Clinical signs were evident for approximately 2 weeks prior to referral. Both eyes were affected in 4 cats. Mean healing time of ulcers treated with superficial debridement was 30 days. Mean healing time of ulcers treated with superficial debridement and grid keratotomy was 42 days. Superficial keratectomy was performed on 2 eyes and resulted in a healing time of 2 weeks. Formation of a corneal sequestrum was evident in 2 of 21 eyes treated with superficial debridement. Formation of a corneal sequestrum was evident in 4 of 13 eyes treated with superficial debridement and grid keratotomy. CONCLUSIONS AND CLINICAL RELEVANCE: Brachycephalic cats appear to be predisposed to developing nonhealing corneal ulcers. The combination of superficial debridement and grid keratotomy did not decrease mean healing time of nonhealing ulcers, compared with superficial debridement alone. Grid keratotomy may predispose cats with corneal ulcers to develop a corneal sequestrum.     

Topical treatment of non-healing corneal epithelial ulcers in dogs with aminocaproic acid

The potential efficacy of topical epsilon-aminocaproic acid, an antiplasmin agent, in the treatment of persistent corneal epithelial defects was evaluated in a study of the medical records of 44 dogs, in which 51 eyes had been diagnosed with a corneal epithelial defect lasting more than 10 days, with no apparent underlying cause. At an initial examination all the affected eyes had had non-adherent epithelium removed. Thirty-four of the eyes in 28 dogs examined between January 2000 and March 2003 were also treated by the topical application of a solution of 35.7 mg/ml ophthalmic aminocaproic acid three times a day; the other 17 eyes in 16 dogs treated between October 1997 and March 1999 had received only topical treatment with gentamicin in addition to the debridement. Both groups were assessed clinically at weekly intervals for a maximum of three weeks. The two groups had approximately the same breed distribution, and there were no statistically significant differences between them in terms of their age, sex, affected side or duration of the corneal erosions. After three weeks, 32 of the 34 eyes treated with aminocaproic acid (94.1 per cent) had been cured, compared with seven of the 17 eyes treated with gentamicin (41.2 per cent) (P=0.0001). No adverse drug reactions were reported.     

Corneal epithelial inclusion cyst in the dog

Unilateral corneal epithelial inclusion cysts are recorded in a series of 16 dogs. The cysts were not congenital, there was no breed incidence, and in 11 patients there was history of corneal trauma or ulceration before cyst formation. There was some variability in clinical presentation, and sight was affected in six dogs. Fifteen patients were treated successfully by superficial keratectomy without cyst recurrence.     

Conjunctival dermoid in two guinea pigs: a case report

Clinical and histologic findings of conjunctival dermoids in two unrelated guinea pigs are described. The dermoids were treated surgically by resection with superficial lamellar keratectomy and corneal epithelial debridement. Histologically the dermis underneath a stratified squamous keratinized and variably pigmented epithelium consisted of multiple hair follicles, with clearly visible arrectores pilorum muscles, sebaceous glands and loose vascularized fatty tissue.     

Clinical management of superficial complicated corneal ulcerations infected with newly identified fastidious bacteria with unknown antibiotic sensitivity in three horses

This case series addresses a clinical approach to a specific type of infected corneal ulceration in horses; the slow-healing superficial complicated corneal ulceration involving a fastidious or possibly newly identified bacteria for which no antibiotic sensitivity can be determined. These corneal ulcerations present as superficial, nonhealing lesions that appear infected based on cellular infiltration of the cornea. Because they are superficial, they do not appear to be as serious to the referral veterinarian as deep stromal corneal ulcerations. However, superficial corneal ulcerations are complicated and slow healing, ultimately frustrating both owners and primary care clinicians. Culture results are often negative, or implicate a newly identified bacteria with no known antimicrobial sensitivity in horses.     

Histopathologic evidence of capecitabine corneal toxicity in dogs

In an experimental model of transplant rejection, renal transplants were performed on 6 mixed-breed dogs. Capecitabine (CPC) was administered as an oral immunosuppressive agent. All recipients received systemic CPC, cyclosporine (CSA), prednisolone, and famotidine throughout the study. Two dogs developed superficial keratitis, which was characterized by multifocal geographic erosions, superficial corneal epithelial pigmentation, and corneal neovascularization. These clinical signs correlated with the dose of CPC given, whereas other drug doses remained unchanged. After euthanasia, routine histologic sections were stained with hematoxylin and eosin and with alcian blue periodic acid-Schiff for light microscopic evaluation. Ocular histopathologic abnormalities were limited to neovascularization and inflammatory infiltrate of the anterior corneal stroma and abnormal basal cell morphology, disorganization, thinning, and pigmentation of the corneal epithelium. The purpose of this communication is to describe the clinical and histopathologic evidence of CPC corneal toxicity in dogs.     

A novel herpesvirus associated with chronic superficial keratitis and proliferative conjunctivitis in a great horned owl (Bubo virginianus)

An adult great‐horned owl (Bubo virginianus; GHOW) presented with a history of recurrent corneal ulceration of the right eye (OD). Findings included ulcerative superficial keratitis, proliferative conjunctivitis, and iris pigmentary changes. The ulcer was initially nonresponsive to medical therapy, but showed rapid and appropriate healing following diamond burr debridement. Proliferative conjunctivitis markedly improved following topical antiviral therapy with cidofovir 1%, interferon alpha 2B ophthalmic solutions, and oral l ‐lysine. Histopathologic evaluation of a conjunctival biopsy revealed epithelial features suspicious for viral cytopathic changes and intranuclear structures suspicious for viral inclusions, suggestive of a possible viral‐induced papillomatous conjunctivitis. A novel alphaherpesvirus, referred to as Strigid Herpesvirus 1 (StrHV1), was identified using PCR and gene sequencing. This case represents a new clinical manifestation of a previously unreported herpesvirus in the GHOW. Identification of the herpes virus was critical to administration of appropriate therapy and resolution of the conjunctivitis, and corneal epithelial debridement promoted resolution of the chronic corneal epithelial defect.     

Cyanoacrylate tissue adhesive for treatment of refractory corneal ulceration

Isobutyl cyanoacrylate tissue adhesive (BCTA) was used in the treatment of refractory superficial corneal ulcers in 17 dogs, one cat, and one rabbit, present 2 weeks to 7 months (mean 6.8 weeks +/- 6.1) prior to referral. Little to no sedation was required in the majority of cases, with only topical anesthetic applied prior to debridement and BCTA application. The presence of the tissue adhesive caused mild discomfort for several days after application, as reported by the owners. The ulcers healed, and the tissue adhesive sloughed in approximately 3 weeks (+/- 1 week). Mild neovascularization of the cornea resolved with topical corticosteroids. The use of BCTA offers a simple, safe and noninvasive treatment for refractory corneal ulcers.