Corneal stromal abscess in a horse

A thoroughbred yearling presented with a focal, yellow, midstromal corneal opacity with concurrent iridocyclitis which was consistent with a corneal stromal abscess. When continued, appropriate, medical therapy failed to improve the patient's condition, penetrating keratoplasty was performed for diagnosis and therapy. Histopathology showed that the deep corneal stroma and Descemet's membrane were severely infiltrated with necrotic neutrophils and numerous, intralesional fungal hyphae. Culture was negative. Bacteria were not isolated, consistent with a fungal corneal stromal abscess. The resultant corneal scar did not interfere with the horse's racing career.     

Corneal invasion by hemangiosarcoma in a horse

A 15-year-old gray Arabian gelding presented for evaluation of a lateral limbal mass extending across approximately 30% of the cornea. Grossly, the raised mass appeared nonpigmented, smooth, and irregular in shape, with an area of central necrosis and serosanguinous discharge. The mass was removed via lamellar keratectomy and histopathologic evaluation revealed features characteristic of hemangiosarcoma (HSA), including irregular vascular channels lined by a plump spindle cell population. Immunohistochemistry results showed that the neoplastic cells lining the vascular channels present diffuse and strong cytoplasmic reaction with von Willebrand Factor and the perivascular spindle cells exhibit moderate cytoplasmic reaction for smooth muscle actin. A lack of cytokeratin staining definitively excluded a diagnosis of atypical squamous cell carcinoma. Smooth muscle actin staining of the perivascular cells adjacent to the neoplastic endothelial cells is not a feature commonly described in HSA and has not been reported in previous cases of equine HSA. The horse remained in good health 21 months postkeratectomy and has exceeded the survival time of previously documented equine ocular HSA cases where more extreme surgical excision was performed.     

Corneal sensitivity in healthy, immature, and adult alpacas

Objective To determine the corneal sensitivity of healthy, immature, and adult alpacas to establish normal reference values for this species. Animals studied Six normal crias and 18 normal adult alpacas. Procedures Corneal sensitivity was determined by evaluating the corneal touch threshold (CTT) in five regions of the cornea using a Cochet–Bonnet aesthesiometer. The nylon filament length in cm was then converted to applied pressure values in mg/0.0113 mm² and g/mm² using a conversion chart. Results The central region of the cornea was the most sensitive, and the dorsal and temporal regions were the least sensitive in alpacas. There were no significant differences between the right and left eyes or between values in males and females at any site. Crias had significantly greater corneal sensitivity compared with adult alpacas in all five regions of the cornea that were evaluated. Conclusions Normal reference values for CTT in alpacas were established using a Cochet–Bonnet aesthesiometer. The central region of the cornea is the most sensitive in alpacas, and crias have higher corneal sensitivity than adult alpacas.     

Measurement of corneal sensitivity in 20 ophthalmologically normal alpacas

Objective To determine corneal sensitivity in 20 healthy adult alpacas (40 eyes) in order to establish reference values. Design Prospective study. Animals Twenty healthy, adult alpacas. Procedures Corneal sensitivity was determined by the corneal touch threshold (CTT) using a Cochet‐Bonnet esthesiometer. Five different regions of the cornea were evaluated (nasal, ventral, lateral, dorsal, and central). Results Corneal touch threshold values (in mm filament length) obtained from five corneal regions demonstrated varying corneal sensitivities. The central region (34.5 ± 7.1 mm) was the most sensitive, followed by the ventral (29.5 ± 7.2 mm), medial (29.3 ± 7.3 mm), dorsal (25.6 ± 6.3 mm), and lateral (21.8 ± 5.7 mm) regions. All pairwise comparisons of regional differences were statistically significant (P < 0.05), except for the comparison between the ventral and medial regions (P = 0.88). Evaluation of the CCT while controlling for age (2–5 years vs. 6–10 years) demonstrated an increased CTT with an increasing age for the central, ventral, medial and lateral regions. A decrease in the CTT of the dorsal region was noted with increasing age. Conclusion and Clinical Relevance Corneal touch threshold values in 40 eyes of 20 healthy adult alpacas were determined using a Cochet‐Bonnet esthesiometer. This study demonstrated the central corneal region to be most sensitive. Values obtained may serve as reference values in subsequent studies.     

Cochet-Bonnet aesthesiometer-determined corneal sensitivity in neonatal foals and adult horses

Corneal touch threshold (CTT) was measured in sick neonatal foals, healthy foals, and healthy adult horses with a Cochet-Bonnet aesthesiometer. The mean overall CTT for the adult horses, sick foals, and healthy foals was 4.82 +/- 0.87 cm, 3.21 +/- 0.24 cm, and 5.01 +/- 0.61 cm, respectively. The central cornea of adult horses was more sensitive than the limbal cornea. Corneal sensitivity was significantly reduced in sick neonatal foals compared to adults. The mean Schirmer I tear test values were significantly lower in foals than adults, and were 14.2 +/- 1.0 mm, 12.8 +/- 2.4 mm, and 18.3 +/- 2.1 mm wetting in sick neonatal foals, normal neonatal foals, and adult horses, respectively. Reduced corneal sensation and lower tear production may be associated with ulcerative keratitis and slow corneal healing in some foals.     

Episodic collapse in the horse

The term ‘collapse’ can be used to describe a variety of incidents in which a horse loses postural tone with or without progression to recumbency and with or without loss of consciousness. Depending on the aetiology of the condition the episode may be self‐limiting and may or may not recur. Alternatively the collapse may be secondary to serious injury or disease and require veterinary intervention. This article mainly discusses investigation of the former scenario of self‐limiting single or multiple episodes of collapse in apparently healthy horses. An overview of the various causes of collapse is followed by a suggested approach to the diagnosis of these challenging cases.     

An overview of recent developments in corneal immunobiology: potential relevance in the etiogenesis of corneal disease in the horse

This paper overviews some recent developments in mammalian corneal immunobiology, and discusses how these may act as pointers towards understanding the immunology underlying some common corneal diseases in the horse, including infectious ulceration and presumptively immune-mediated non-ulcerative disease. Specifically, three aspects of corneal immunobiology are examined: the role of Toll-like receptors in surface immunity and in the etiogenesis of microbial ulceration, the relationship between conjunctiva associated lymphoid tissue (CALT) and immunoprotection of the corneal surface, and the mechanisms determining corneal immune privilege (IP) and how down regulation of IP may be an important factor in the genesis of corneal immunoinflammatory disease.     

Haemangiosarcoma in the horse

Neoplasms arising from vascular endothelial cells include benign haemangioma and malignant haemangiosarcoma, both of which are rare in the horse. Haemangiosarcoma can arise as a solitary mass, typically involving the eye or skin, or as disseminated tumours throughout multiple organs. There is no sex, breed or age predilection but most cases are found in middle aged horses. Clinical presentations of haemangiosarcoma in the horse include the presence of a visible mass or reflect dysfunction of the organ involved, thus making it difficult to differentiate from other neoplasms. Ante mortem diagnosis through clinicopathological findings, cytological findings of body cavity effusions or fine needle aspirates are often unrewarding. Biopsy or mass submission for histopathological examination may aid in diagnosis of haemangiosarcoma. A majority of cases are diagnosed post mortem; however, if the mass is poorly differentiated additional diagnostics such as immunohistochemical staining may be needed. Unfortunately, treatment of haemangiosarcoma is often unrewarding and limited based on the location of the mass and the aggressive nature of this neoplasm.     

Corneal epithelial inclusion cyst in a Llama

A 13-year-old, female Llama presented for evaluation of a limbal based corneal mass involving the OD of 4 months duration. The mass was excised en bloc by a nonpenetrating keratectomy, followed by placement of a conjunctival advancement flap covering the keratectomy site. The mass was submitted for histological evaluation. Histopathology identified the mass to be a corneal epithelial inclusion cyst filled with necrotic squamous and neutrophilic debris. Surgical excision was complete and considered curative with no signs of recurrence 3 months postoperatively. There was no known prior ocular trauma; however, a previously performed corneal biopsy for evaluation of recurrent epithelial erosions may have been an initiating cause.     

Caffeine clearance in the horse

The pharmacokinetic properties of intravenously administered caffeine were studied in 10 horses using a commercially available automated enzyme immunoassay. The harmonic mean for the distribution half-life was 5.2 min (range 1.4–18.7). The harmonic mean for the elimination half-life was 10.18 h (range 6.82–20.92). The harmonic mean of the volume of distribution was 0.32 L/kg (range 0.22–0.53). There was no correlation between the dose of caffeine/kg body weight and the elimination half-life (Spearman's coefficient of rank correlation =0.19).Abbreviations AUC area under the serum concentration-time curve - AUMC area under the moment curve - BSP sulphobromophthalein - ICG indocyanine green - SD standard deviation - t _1/2 elimination half-life - V _c apparent volume of the central compartment - V _d(ss) apparent volume of distribution at steady state     

Corneal transplantation for inflammatory keratopathies in the horse: visual outcome in 206 cases (1993-2007)

Objective To evaluate the visual outcome of three techniques of corneal transplantation surgery in treating severe inflammatory keratopathies in the horse. Design Retrospective medical records study. Animals studied Medical records of 206 horses that received corneal transplantation surgery at the University of Florida Veterinary Medical Center from 1993 to 2007 were reviewed. Procedure Data collected from the medical records included signalment, types of ocular lesions, type of transplant surgery performed, length of follow‐up, complications, and visual outcomes. Results Full thickness penetrating keratoplasty (PK) was performed in 86 horses for melting ulcers, iris prolapse/descemetoceles, and medically nonresponsive full thickness stromal abscesses (SA). Posterior lamellar keratoplasty (PLK) and deep lamellar endothelial keratoplasty (DLEK) are split thickness penetrating keratoplasties that were utilized for medically nonresponsive deep stromal abscesses (DSA) in 54 and 66 eyes, respectively. The most common postoperative surgical complication was graft rejection and varying degrees of graft opacification. Wound dehiscence and aqueous humor leakage was also a common postoperative problem. A positive visual outcome was achieved for PK, PLK, and DLEK in 77.9%, 98.1%, and 89.4%, respectively. Conclusions Corneal transplantation is a tectonically viable surgery in the horse with an overall success rate of 88.5% in maintaining vision when treating vascularized and infected corneal disease in the horse.     

Uveitic glaucoma in the horse

Glaucoma is a serious complication of anterior uveitis that can result in significant ocular discomfort and loss of vision. As glaucoma is insidious and mostly asymptomatic until late in the course of disease, it is often undiagnosed. Equine recurrent uveitis is the most common underlying disorder: it is a disease of high prevalence, characterised by recurrent‐remitting episodes of ocular inflammation. Here, the inflammatory cells and mediators they release alter the normal anatomic structure of the anterior chamber and aqueous drainage pathways of the eye. These changes alter the homeostatic mechanisms of intraocular pressure control. Management of glaucoma secondary to uveitis can be challenging due to the difficulties of managing the underlying disorder and its effects on the eye. This article reviews the pathogenesis of uveitic glaucoma in the horse and medical and surgical management options.