The search for causes of nonhealing or recurrent ulcerative keratitis in horses

Chronic or recurrent superficial ulcerative keratitis in horses is common and the causes of these lesions must always be searched for and identified by the clinician. Without appropriate elimination of the underlying cause, the ulcerative keratitis may not resolve, resulting in corneal scarring, decreased vision and possibly loss of the eye. Common causes of chronic or recurrent superficial ulcerative keratitis, such as infectious keratitis, should always be ruled out; however, other possible causes such as single or multiple distichiasis, should be considered.     

Aortic rupture and aorto‐pulmonary fistulation in the Friesian horse: Characterisation of the clinical and gross post mortem findings in 24 cases

Reasons for performing study: In horses, aortic sinus of Valsalva aneurysms or tears in the aortic root are well‐recognised conditions in breeding stallions, often leading to sudden death. A more uncommon form of aortic rupture, located proximal to the ligamentum arteriosum has been reported in 3 Friesian horses. Objectives: The purpose of this study was to phenotypically characterise aortic rupture and aorto‐pulmonary fistulation in Friesian horses in terms of clinical and post mortem data based on 24 cases. Methods: Friesian horses that were diagnosed with aortic rupture and aorto‐pulmonary fistulation over a period of 13 years (1997–2010) at the Department of Equine Sciences of Utrecht University (n = 15) and Wolvega Equine Hospital (n = 9), were included in this study. Case history, results of clinical examination and gross post mortem findings were screened and analysed. Results: Some cases were found dead without prior symptoms, but in several cases signs such as recurrent colic, peripheral oedema and sustained tachycardia were present for several weeks prior to cardiac failure. Clinical examination during hospitalisation revealed increased rectal temperature, peripheral oedema and increased jugular pulse with a bounding arterial pulse. In the majority of horses an aortic rupture of the aortic arch near the ligamentum arteriosum, concurrent with a circumferential cuff of perivascular haemorrhage and aorto‐pulmonary fistulation, was found at post mortem examination. Conclusions: Aorto‐pulmonary fistulation in conjunction with aortic rupture is more common in Friesians than previously estimated. In some cases findings demonstrate a progressive pathology rather than acute cardiac failure and sudden death. An appropriate approach is necessary during post mortem examination of the heart in order not to overlook the diagnosis. Potential relevance: Equine practitioners should realise that in Friesian horses presented with a history of recurrent false colic, coughing, sustained tachycardia and/or peripheral oedema, aortic rupture and aorto‐pulmonary fistulation should be included in the differential diagnosis.     

Equine laminitis model: Cryotherapy reduces the severity of lesions evaluated seven days after induction with oligofructose

Reasons for performing study: A previous preliminary study demonstrated the potential of distal limb cryotherapy (DLC) for preventing laminitis. Clinically, DLC must be effective for periods longer than 48 h and the preventive effect must extend beyond its discontinuation. Objectives: To evaluate the effect of DLC, applied during the developmental phase of induced laminitis, on the severity of clinical laminitis and lamellar histopathology 7 days after dosing. Methods: Eighteen normal Standardbred horses were divided into 3 groups of 6. Continuous cryotherapy was applied for 72 h to the distal limbs of the first group. The second and third groups were administered laminitis inducing doses of oligofructose and 72 h of cryotherapy applied (immediately after dosing) to the second group. After clinical assessment all horses were subjected to euthanasia 7 days after dosing and hoof lamellar tissues were harvested and analysed. Results: In the laminitis induced horses clinical lameness and laminitis histopathology was significantly reduced in horses that underwent 72 h of DLC compared with untreated controls. Cryotherapy alone produced no significant lameness or other ill effect. Conclusions: Continuous, medium‐ to long‐term (72 h) cryotherapy applied to the distal limbs of horses safely and effectively ameliorates the clinical signs and pathology of acute laminitis. Potential relevance: Pre‐emptive distal limb cryotherapy is a practical method of ameliorating laminitis in ill horses at risk of developing the disease.     

Corneal ulceration in a dog following exposure to the defensive spray of a walkingstick insect (Anisomorpha spp.)

Objective – To describe a case of corneal ulceration in a dog resulting from ocular exposure to the defensive spray of a walkingstick insect (Anisomorpha spp.). Case Summary – A 4‐year‐old, male Chihuahua in southeastern Louisiana presented to an emergency veterinary hospital approximately 20 hours after it was witnessed to have come in close proximity to a walkingstick insect. Within seconds of approaching the insect, the dog yelped, jumped backwards and developed lacrimation, blepharospasm, and periocular swelling of the left eye. Upon presentation, the dog was found to have blepharospasms and miosis of the left eye. Fluorescein stain was applied to the affected eye and diffuse corneal uptake of stain was noted. A diffuse superficial corneal ulceration was diagnosed and treated supportively with ocular flushing, topical antibiotics, ocular lubrication, and a 1% solution of ocular atropine, as well as systemic nonsteroidal anti‐inflammatory agents. Clinical signs resolved 10 days after injury. New or Unique Information Provided – While most species of walkingstick insects are considered harmless, certain species in the southeastern United States have the ability to spray defensive venom at their predators. Upon ocular exposure to the venom, the victim may experience intense pain followed by blurred vision, conjunctivitis, keratitis, and corneal ulceration. To date, there is only 1 previous reported case of ocular exposure to walkingstick venom in a dog although both children and animals may be at higher risk for ocular exposure due to their curious nature and proximity in size to the insect. Superficial corneal and conjunctival damage can occur following direct exposure to the defensive chemical spray of the Northern and Southern Twostriped walkingstick insects found in the southeastern United States and may be considered a differential diagnosis in cases involving diffuse corneal ulceration.     

Outcome of superficial keratectomy without conjunctival graft as a surgical technique for immune-mediated keratitis in horses: Four cases

This case report describes four horses with unilateral superficial or mid-stromal immune-mediated keratitis (IMMK) treated with a superficial keratectomy (SK) without a conjunctival graft. In two horses, the surgery was performed under general anaesthesia, and in two horses standing with sedation and local blocks. Results of this report show that SK is a viable treatment option in horses with chronic superficial and/or mid-stromal IMMK that can even be performed in the standing, sedated horse. When sufficient corneal tissue is removed, no recurrence is to be expected in the long-term follow-up (up to 31 months). In two horses, healing occurred without complications. Two horses developed a secondary bacterial infection post-operatively (Enterococcus faecalis and Staphylococcus aureus). In one case, this resulted in a pre-perforating melting corneal ulcer necessitating conjunctival pedicle graft surgery 13 days post keratectomy. In three horses, there was no recurrence of the IMMK with a long-term follow-up of 6–31 months. One case showed recurrence of IMMK in the cornea region surrounding the keratectomy 9 months after surgery.     

Bacteroides sp. as a cause of anaerobic keratitis in a pony

This Case Report describes anaerobic infection of the conjunctiva and cornea in a pony. A 13‐year‐old pony was admitted for evaluation following suspected ocular trauma. Bacterial conjunctivitis and keratitis were diagnosed based on clinical appearance of the eye and cytological evaluation of a corneal scraping. The pony responded poorly to topical therapy, and enucleation was performed. Culture of the corneal scraping yielded Corynebacterium sp. and Bacteroides sp. Anaerobic keratitis and conjunctivitis is uncommonly reported in horses, but should be suspected when there is a history of ocular trauma or skin disease, or when a malodorous ocular discharge is identified.     

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.     

Prevalence of Ocular Disorders in an Indian Population of Horses

The objective of this clinical study was to report the prevalence of ocular disorders in a large population of horses from the Indian army. Both eyes of 500 horses were examined using a direct ophthalmoscope and by a transillumination procedure. Intraocular pressures were measured in several study horses. Fluorescein dye, Schirmer tear test, and menace testing were performed when indicated. Corneal culture swabs were collected from horses affected with corneal ulcers found on ophthalmoscopic examination. A total of 100 horses were found to be affected with some form of ocular disorder. The eye problems recorded were congenital eye lid disorders (2%) and included a subcutaneous cyst in the lower eye lid and slit in upper eye lid; conjunctivitis (12%); chronic interstitial keratitis (30%); a parasite in the anterior chamber (1%), which was however not removed for genus and species identification; phthisis bulbi (1%); uveitis (24%); glaucoma (13%); cataracts (3%); unilateral retinal hemorrhage (1%); luxation of cataractous lens (3%); posterior synechia (2%); and corneal ulceration (8%). Pseudomonas spp was the most common bacteria identified in horses affected with corneal ulceration. Vision-threatening ocular disorders are high in Indian army horses; this is a cause of major concern for the rider and the horse and, therefore, it is important to include ocular examination in horses as part of a routine and complete physical examination.     

Treatment of corneal ulceration and bullous keratopathy using a nictitating membrane flap in two horses

Objective

The aim of this study was to describe placement of a nictitating membrane flap as a treatment for corneal ulceration and bullous keratopathy in two horses.

Animals Studied

A 13-year-old American Saddlebred mare presented for severe corneal edema, superficial stromal ulceration, and a central bulla of the left eye. A 4-year-old Trakhener stallion also presented with a large axial bulla of the left eye with concurrent severe corneal edema and a deep stromal ulcer.

Procedure

A complete ophthalmic examination was performed. Samples were obtained for corneal cytology, and both horses were started on aggressive medical therapy. Both underwent general anesthesia for placement of a nictitating membrane flap and a subpalpebral lavage system (SPLS).

Results

Corneal cytology for each horse revealed a mixed bacterial population. Moderate Pseudomonas aeruginosa was cultured from the mare, while Aspergillus species and a few Enterococcus gallinarum were cultured from the stallion. The bullae in both horses resolved at 3 and 4 weeks and vision returned in the affected eye 4.5 and 3 months postoperatively at the last follow-up, respectively.

Conclusion

Aggressive medical management with concurrent placement of a nictitating membrane flap is effective to treat bullous keratopathy in two horses. The described treatments could be used to treat horses that develop severe or progressive bullous corneal lesions.     

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.     

Keratitis and periocular lesions associated with equine herpesvirus‐3 in a 3‐month‐old filly

A 3‐month‐old Quarter Horse filly presented with corneal ulceration in the right eye with extensive coalescing periocular ulcerations, erosions, and cutaneous crusts. Similar periocular lesions were present around the left eye, on the gingival mucosa, and on the cutaneous and mucosal surfaces of the lips. Based on the severity of the filly's corneal lesions, expense and duration of treatment, euthanasia was elected. Histological post mortem examination revealed numerous hyperplastic and/or dysplastic epithelial cells adjacent to areas of ulceration and erosion with intranuclear viral inclusion bodies. Equine herpesvirus‐3 (EHV‐3) was identified by polymerase chain reaction from the right cornea and lip. The virus was isolated from the right cornea, right eyelid and lip. The dam presented with multifocal to coalescing perineal vesicles. EHV‐3 was confirmed by polymerase chain reaction from the vulvar lesions and the mare recovered spontaneously. This is the first case of EHV‐3 corneal infection reported in horses and emphasises that EHV‐3 should be included as a differential diagnosis for vesicular lesions involving the equine periocular and oronasal epithelium.     

Primary corneal melanocytoma in a Collie

A 6‐year‐old female, spayed Collie was referred to the Western College of Veterinary Medicine for a 12‐month history of a progressive right corneal mass. A superficial keratectomy was performed and histopathology revealed a corneal melanocytoma with complete excision. There has been no recurrence of the neoplasm to date (12 months). This is the first known report of an isolated corneal melanocytoma in a canine.     

Bilateral hypoplasia of the minor tubercle of the humerus with medial luxation of the biceps tendon in two Quarter Horses

Two Quarter Horses were examined at the Washington State University Veterinary Teaching Hospital with forelimb lameness. Case 1 was a 4‐year‐old female with a 4 month history of intermittent forelimb lameness that had partially responded to oral anti‐inflammatories. The horse was in full training and actively competing in cutting. Case 2 was a one‐year‐old filly bred for cutting that presented with a right forelimb lameness of 3 weeks’ duration, which was not responsive to oral anti‐inflammatories. The horse was not in training. On lameness examination, Case 1 was grade 1/5 (American Association of Equine Practitioners scale) lame in the left forelimb in a straight line on a hard surface, extension and flexion of the shoulder was resented and exacerbated the lameness. Case 2 was grade 3/5 lame in the right forelimb in a straight line on a hard surface, flexion and extension of the shoulder was resented and exacerbated the lameness. Both horses had a characteristic dished appearance to the dorsal aspect of the shoulder, with prominence of the proximal aspect of the humerus. Ultrasound and proximodistal oblique (skyline) radiographic views of the scapulohumeral joints demonstrated bilateral hypoplasia of the minor tubercle of the humerus with bilateral medial luxation of the proximal biceps tendon in both cases. To the authors' knowledge this is the first report of 2 cases of bilaterally affected horses, as well as the first report of the condition in the Quarter Horse breed.     

Osseous metaplasia in the conjunctiva of a horse presenting with recurrent ulcerative keratitis

A 13‐year‐old Thoroughbred gelding presented with a 6 month history of recurrent conjunctivitis, dacryocystitis and corneal ulceration affecting the left eye (OS). Treatment had included multiple topical antibiotic and anti‐inflammatory preparations, nasolacrimal system flushing and an injection of methylprednisolone acetate (MPA) (Depomedrone) ¹ administered subconjunctivally into the left lower eyelid. No mechanical cause for the ulcerative keratitis could be visualised but digital palpation revealed a firm linear structure in the central palpebral conjunctiva of the lower eyelid. An excisional biopsy was performed and histopathological examination revealed the lesion to be a region of osseous metaplasia. Following excision of the lesion, the corneal ulcer resolved and the eye remained disease free over a 4 year follow‐up period. A causal link between the osseous metaplasia and the recurrent ulcerative keratitis was therefore suspected. This report describes the management of this case and discusses the pathogenesis of osseous metaplasia and the use of subconjunctival corticosteroids.     

Combined keratectomy, strontium-90 irradiation and permanent bulbar conjunctival grafts for corneolimbal squamous cell carcinomas in horses (1990-2002): 38 horses

OBJECTIVE: The purpose of this study was to evaluate the effectiveness of postoperative beta-irradiation with strontium-90 as an adjunctive treatment to superficial keratectomy and permanent bulbar conjunctival graft for removal of equine corneolimbal squamous cell carcinoma (SCC), in decreasing recurrence rate. STUDY: The retrospective case study included 38 horses diagnosed and treated for SCC of the eye that involved the limbus and/or cornea. The patients were treated between 1990 and 2002, with strontium-90 irradiation immediately after corneal and conjunctival graft surgery. Recurrence was defined as the postoperative and postirradiation regrowth of SCC in the same site and globe that was previously treated. RESULTS: The Appaloosa was the most commonly represented breed and horses that had more than one base coat color represented the majority of the cases (53%). The coat colors of white, chestnut/sorrel and gray were the most commonly represented colors of the horses treated. Eight horses (21%) could not be assessed for tumor recurrence due to lack of two or more post-treatment examinations, and another horse was enucleated 6 days postoperatively due to progressive corneal ulceration. Twenty-four horses (63% of the entire study population; 83% of the followed cases) had a mean +/- SD of 1754 +/- 1319 days without tumor recurrence, ranging from 14 days to 5110 days. Five horses (13% of the entire study population; 17% of the assessed horses) had tumor recurrence at a mean +/- SD of 449 +/- 339 days with a range of 29 days to 900 days. For the five recurrences, treatment included local excision (n = 1), enucleation (n = 2), and additional strontium-90 therapy (n = 3). CONCLUSIONS: The combination of superficial keratectomy, beta-irradiation and permanent bulbar conjunctival grafts for limbal, corneal or corneolimbal SCC in horses is effective in at least 83% of the horses. Recurrence occurred in about 17% of the horses. Multiple biannual re-examinations are recommended to observe for tumor recurrence.     

Amniotic membrane transplantation for corneal surface reconstruction after excision of corneolimbal squamous cell carcinomas in nine horses

OBJECTIVE: The purpose of this study was to evaluate the usefulness and effectiveness of permanent amniotic membrane transplantation as an adjunctive treatment to superficial keratectomy alone or combined with strontium-90 irradiation for treatment of equine corneolimbal squamous cell carcinoma (SCC) to decrease corneal scarring and recurrence rate. STUDY: The retrospective case study included 11 horses (n = 12 eyes) diagnosed and treated for ocular SCC that involved the limbus and cornea. Nine of those horses (n = 9 eyes) were treated between 2002 and 2006, with superficial lamellar keratectomy alone or combined with strontium-90 irradiation and followed by placement of a permanent amniotic membrane graft in the surgical defect. The level of scarring (i.e. the clarity of the cornea) resulting with the use of amniotic membrane was subjectively compared to cases where a permanent bulbar conjunctival graft was performed following keratectomy combined with strontium-90 irradiation or cryotherapy (n = 3 eyes). Recurrence was defined as the postoperative and postirradiation regrowth of SCC in the same site and globe. RESULTS: The nine horses that received an amniotic membrane graft after keratectomy alone or combined with irradiation showed a minimal level of scarring in a cornea that regained a greater transparency in comparison to the horses that were treated with a bulbar conjunctival graft. All of the horses that received an amniotic membrane graft had 226 +/- 218 days of follow-up without tumor recurrence (mean +/- SD), ranging from 21 days to 778 days. CONCLUSIONS: The combination of superficial keratectomy alone or associated with beta-irradiation and permanent amniotic membrane transplantation is an effective treatment of corneal or corneolimbal SCC in horses. The placement of an amniotic membrane material represents an alternative surgical procedure to bulbar conjunctival grafts, especially if there is a lack of bulbar conjunctiva tissue available after tumor resection or if a particularly large corneal resection is necessary. The amniotic membrane is incorporated into the corneal defect and seems to create noticeably much less scarring than a corneal defect covered by bulbar conjunctiva.     

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.     

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.     

Pyogenic granuloma of the cornea in a pony: Uncommon complication of corneal wound healing

A 6-year-old miniature Shetland pony mare was referred for evaluation of a left corneal mass, which developed from the healing tissue of a corneal traumatic ulceration that had occurred 4 weeks previously. On gross examination, a spherical, smooth-surfaced, and pink-colored lesion of about 1 cm in diameter was protruding from the left palpebral fissure. Ophthalmic examination revealed that it was attached to the scar tissue of the cornea, and that one corpora nigra was adherent to the posterior face of corneal wounded area, without sign of uveitis. The remainder of the ophthalmic examination was unremarkable. The mass was excised, and cryotherapy was used as an adjunctive therapy. Histopathology of the resected mass was consistent with a pyogenic granuloma on the basis of radially oriented proliferating capillaries, embedded in immature granulation tissue containing an infiltrate of neutrophils, plasma cells and eosinophils. There were no histological features of malignancy. 2 months after surgery, the ventral part of the fibrotic corneal scar was slightly raised by a pink tissue, suggesting possible recurrence of the initial lesion. A second cryotherapy was performed over the leukoma area. No recurrence has been noted for a follow-up period of more than 25 months. Pyogenic granuloma is a benign proliferative fibrovascular response that typically develops after trauma or surgery. Corneal involvement is rare in humans, and to the authors' knowledge has never been documented in veterinary ophthalmology.