Qualitative tear film disease

Abnormalities of the lipid and mucin components of the preocular tear film may result from diseases of the eyelid margins and conjunctiva. Chronic keratoconjunctivitis with epithelial edema and superficial corneal neovascularization, with or without ulceration, characterizes qualitative tear diseases. Tear components other than lipid and mucin that carry probable clinical significance include tear proteins, all-trans retinal, cholesterol, glucose, and electrolytes. Although less common than quantitative or aqueous deficiencies, qualitative abnormalities are recognized as primary or secondary causes of ocular surface disease in companion animals.     

Microstructure and glycosaminoglycan ratio of canine cornea after reconstructive transplantation with glycerin-preserved porcine amniotic membranes

Objective  Although amniotic membranes of canine, feline, and equine species have some advantages as corneal transplantation material in many canine ocular diseases, their softness, thinness, and low availability can pose problems. As an alternative, the more abundant porcine amniotic membranes may be used. This paper describes the use of glycerin-preserved porcine amniotic membranes in corneal transplantation in eight normal dogs.
Method  A 0.4-mm deep recipient bed in the axial cornea of the OS of all dogs was created using an 8-mm Barron radial vacuum trephine. The recipient bed was then filled with amnion, and the entire cornea was covered with another piece of the glycerin-preserved membrane. The ocular signs evaluated were corneal opacity and corneal vascularization. The dogs were euthanized on days 5, 10, 20, or 40 after surgery, and samples were collected to evaluate corneal thickness, parenchymal cell number, mean collagen fibril diameter, collagen fibril content and the glycosaminoglycan (GAG) ratio.
Results  Corneal opacity was observed immediately after surgery. Restoration of corneal transparency, regression of corneal vascularization, and visualization of the pupil and iris were noted on day 40.
Conclusions  The clinical observations were supported histologically by regained corneal thickness, parenchymal cell number, mean collagen fibril diameter, collagen fibril content, and GAG ratio, suggesting that this technique may be a novel method for the treatment of ocular surface disorders.     

Identification of putative orthologs of clinically relevant antimicrobial peptides in the equine ocular surface and amniotic membrane

Objectives

This study aimed to define the antimicrobial peptide (AMP) expression pattern of the equine ocular surface and amniotic membrane using a targeted qPCR approach and 3'Tag-sequencing. It will serve as a reference for future studies of ocular surface innate immunity and amniotic membrane therapies.

Procedures

A targeted qPCR approach was used to investigate the presence of orthologs for three of the most highly expressed beta-defensins (DEFB1, DEFB4B, and DEFB103A) of the human ocular surface and amniotic membrane in equine corneal epithelium, conjunctiva, and amniotic membrane. 3'Tag-sequencing was performed on RNA from one sample of corneal epithelium, conjunctiva, and amniotic membrane to further characterize their AMP expression.

Results

Equine corneal epithelium, conjunctiva, and amniotic membrane expressed DEFB1, DEFB4B, and DEFB103A. DEFB103A was expressed at the highest amounts in corneal epithelium, while DEFB4B was most highly expressed in conjunctiva and amniotic membrane. 3'Tag-sequencing from all three tissues confirmed these findings and identified expression of five additional beta-defensins, 11 alpha-defensins and two cathelicidins, with the alpha-defensins showing higher normalized read counts than the beta-defensins.

Conclusions

This study identified AMP expression in the equine cornea and conjunctiva, suggesting that they play a key role in the protection of the equine eye, similar to the human ocular surface. We also determined that equine amniotic membrane expresses a substantial number of AMPs suggesting it could potentiate an antimicrobial effect as a corneal graft material. Future studies will focus on defining the antimicrobial activity of these AMPs and determining their role in microbial keratitis.     

兽医眼表移植学及植片材料的研究进展

角膜疾病是动物最常见的眼科疾病之一,治疗不当将引起视力减退、致盲甚至眼球摘除,给动物带来巨大的痛苦与生活障碍。兽医眼表移植手术经历了多年的研究探索与改良,成为治疗动物角膜损伤、挽救眼球甚至恢复视力的有效方法。不同的手术方式与移植材料对于角膜愈合、免疫排斥、光学性以及眼球形态产生深远的意义和影响。现就各种眼表移植技术以及植片材料在动物角膜疾病中的适应症、应用特点以及预后等方面的研究进展进行综述,旨在为兽医眼科相关疾病的临床治疗层面提供有意义的指导。     

Genetics of upper and lower airway diseases in the horse

Genetic predispositions for guttural pouch tympany, recurrent laryngeal neuropathy and recurrent airway obstruction (RAO) are well documented. There is also evidence that exercise‐induced pulmonary haemorrhage and infectious diseases of the respiratory tract in horses have a genetic component. The clinical expression of equine respiratory diseases with a genetic basis results from complex interactions between the environment and the genetic make‐up of each individual horse. The genetic effects are likely to be due to variations in several genes, i.e. they are polygenic. It is therefore unlikely that single gene tests will be diagnostically useful in these disorders. Genetic profiling panels, combining several genetic factors with an assessment of environmental risk factors, may have greater value, but much work is still needed to uncover diagnostically useful genetic markers or even causative variants for equine respiratory diseases. Nonetheless, chromosomal regions associated with guttural pouch tympany, recurrent laryngeal neuropathy and RAO have been identified. The association of RAO with other hypersensitivities and with resistance to intestinal parasites requires further study. This review aims to provide an overview of the available data and current thoughts on the genetics of equine airway diseases.     

Nonsteroidal anti-inflammatory drugs in veterinary ophthalmology.

Uveitis is a common sequela to many ocular diseases. Primary treatment goals for uveitis should be to halt inflammation, prevent or control complications caused by inflammation, relieve pain, and preserve vision.Systemic and topical NSAIDs are essential components of the pharmaceutic armamentarium currently employed in the management of ocular inflammation by general practitioners and veterinary ophthalmologists worldwide. NSAIDs effectively prevent intraoperative miosis; control postoperative pain and inflammation after intraocular procedures, thus optimizing surgical outcome; control symptoms of allergic conjunctivitis;alleviate pain from various causes of uveitis; and circumvent some of the unwanted side effects that occur with corticosteroid treatment. Systemic NSAID therapy is necessary to treat posterior uveitis, because therapeutic concentrations cannot be attained in the retina and choroid with topical administration alone, and is warranted when diseases, such as diabetes mellitus or systemic infection, preclude the use of systemic corticosteroids.Risk factors have been identified with systemic and topical administration of NSAIDs. In general, ophthalmic NSAIDs may be used safely with other ophthalmic pharmaceutics; however, concurrent use of drugs known to affect the corneal epithelium adversely, such as gentamicin, may lead to increased corneal penetration of the NSAID. The concurrent use of NSAIDs with topical corticosteroids in the face of significant preexisting corneal inflammation has been identified as a risk factor in precipitating corneal erosions and melts in people and should be undertaken with caution[8]. Clinicians should remain vigilant in their screening of ophthalmic and systemic complications secondary to drug therapy and educate owners accordingly. If a sudden increase in patient ocular pain (as manifested by an increase in blepharospasm, photophobia, ocular discharge, or rubbing)is noted, owners should be instructed to contact their veterinarian promptly.     

Hereditary and congenital ocular disease in the cat

The aim of this review of hereditary and congenital ocular disease in cats is to present an overview of the most common disorders seen in this species, the pathogenesis of the problems and wherever possible, how they are treated. Several defects are common in breeds such as the Persian, Himalayan and Burmese cats and affect the anterior segment of the eye. Examples are agenesis of the eyelids, dermoids, entropion and corneal sequestrum. Other problems such as cataracts, lens luxation and retinal dysplasia, cause problems of the intraocular structures, but are less common in cats compared to dogs. Finally, various parts of the retina and in some diseases other parts of the eye, are specifically affected by hereditary diseases. Examples of these are lysosomal storage disease, Chediak-Higashi syndrome and progressive rod cone degeneration and rod cone dysplasia. Research of the latter two hereditary diseases, both described in the Abyssinian breed of cat, have made affected individuals important animal models for research into comparable diseases of humans.     

Congenital hyposomatotropism in a domestic shorthair cat presenting with congenital corneal oedema

A six-month-old, female, domestic shorthair cat was presented with a history of failure to grow and bilateral corneal opacity caused by corneal oedema. Congenital hyposomatotropism and possible secondary hypothyroidism were diagnosed on the basis of fasting serum levels of insulin-like growth factor-1 and thyroxine levels, respectively. These endocrinopathies are rare in the cat and have not been reported to cause ocular signs. The cat died during investigation of these diseases, and histopathological examination of the eyes showed significantly reduced corneal endothelial cell density and number of corneal epithelial cell layers when compared with age-matched healthy control corneas. These changes were implicated in the development of the corneal oedema.     

Feline corneal disease

The cornea is naturally transparent. Anything that interferes with the cornea's stromal architecture, contributes to blood vessel migration, increases corneal pigmentation, or predisposes to corneal edema, disrupts the corneas transparency and indicates corneal disease. The color, location, and shape and pattern of a corneal lesion can help in determining the underlying cause for the disease. Corneal disease is typically divided into congenital or acquired disorders. Congenital disorders, such as corneal dermoids are rare in cats, whereas acquired corneal disease associated with nonulcerative or ulcerative keratitis is common. Primary ocular disease, such as tear film instability, adenexal disease (medial canthal entropion, lagophthalmus, eyelid agenesis), and herpes keratitis are associated with the majority of acquired corneal disease in cats. Proliferative/eosinophilic keratitis, acute bullous keratopathy, and Florida keratopathy are common feline nonulcerative disorders. Nonprogressive ulcerative disease in cats, such as chronic corneal epithelial defects and corneal sequestration are more common than progressive corneal ulcerations.     

Canine,feline, and equine corneal vascular neoplasia: A retrospective study (2007‐2015)

Corneal vascular neoplasms (hemangioma and hemangiosarcoma) are rare in all species. Reported cases are single case reports in a single species. Archived cases of corneal hemangioma and hemangiosarcoma from dogs, cats, and horses were obtained from the Comparative Ocular Pathology Lab of Wisconsin (COPLOW, Madison, WI), tabulated, and examined. This retrospective study describes the breeds, ages, tumor types, and characteristics of vascular neoplasms that appeared to be primarily corneal in location, in feline, canine, and equine patients, with gross and histologic images. There is a discussion of predisposing factors and speculated association with chronic ocular surface disease.     

Veterinary ocular microbiome: Lessons learned beyond the culture

Ocular pathogens cause many painful and vision‐threatening diseases such as infectious keratitis, uveitis, and endophthalmitis. While virulent pathogens and pathobionts play important roles in disease pathogenesis, the scientific community has long assumed disruption of the ocular surface occurs prior to microbial colonization and subsequent infection. While nonpathogenic bacteria are often detected in corneal and conjunctival cultures from healthy eyes, cultures also frequently fail to yield growth of common ocular pathogens or nonpathogenic bacteria. This prompts the following question: Is the ocular surface populated by a stable microbial population that cannot be detected using standard culture techniques? The study of the microbiome has recently become a widespread focus in physician and veterinary medicine. Research suggests a pivotal symbiotic relationship with these microbes to maintain healthy host tissues, and when altered is associated with various disease states (“dysbiosis”). The microbiota that lives within and on mammalian bodies have long been known to influence health and susceptibility to infection. However, limitations of traditional culture methods have resulted in an incomplete understanding of what many now call the “forgotten organ,” that is, the microbiome. With the introduction of high‐throughput sequencing, physician ophthalmology has recognized an ocular surface with much more diverse microbial communities than suspected based on traditional culture. This article reviews the salient features of the ocular surface microbiome and highlights important future applications following the advent of molecular techniques for microbial identification, including characterizing ocular surface microbiomes in our veterinary species and their potential role in management of infectious and inflammatory ocular diseases.     

Report of the equine herpesvirus-1 Havermeyer Workshop, San Gimignano, Tuscany, June 2004

Amongst the infectious diseases that threaten equine health, herpesviral infections remain a world wide cause of serious morbidity and mortality. Equine herpesvirus-1 infection is the most important pathogen, causing an array of disorders including epidemic respiratory disease abortion, neonatal foal death, myeloencephalopathy and chorioretinopathy. Despite intense scientific investigation, extensive use of vaccination, and established codes of practice for control of disease outbreaks, infection and disease remain common. While equine herpesvirus-1 infection remains a daunting challenge for immunoprophylaxis, many critical advances in equine immunology have resulted in studies of this virus, particularly related to MHC-restricted cytotoxicity in the horse. A workshop was convened in San Gimignano, Tuscany, Italy in June 2004, to bring together clinical and basic researchers in the field of equine herpesvirus-1 study to discuss the latest advances and future prospects for improving our understanding of these diseases, and equine immunity to herpesviral infection. This report highlights the new information that was the focus of this workshop, and is intended to summarize this material and identify the critical questions in the field.     

Tear-deficient and evaporative dry eye syndromes of the horse

Tear-deficient dry eye (keratoconjunctivitis sicca), and evaporative dry eye, with some overlap between these two categories, are two major categories of dry eye recognized in the horse. Careful examination of the eyelid margins, the inner and outer surfaces of the upper and lower eyelids, assessment of blink and third eyelid movement, specific testing of tear production, assessment of corneal sensitivity, and slit-lamp examination of the ocular surface before and after fluorescein dye application is recommended to detect dry eye problems. Rose Bengal dye application is also recommended in many cases. Facial nerve paresis is a possible complicating factor in some instances. Evaporative dry eye deserves closer scrutiny for it may be a contributory factor when ocular surface disease such as keratomycosis is present. Factors which influence ocular surface health need more close examination in horses.     

Back problems. Chiropractic evaluation and management.

A thorough knowledge of equine spinal anatomy, biomechanics, and potential pathology is required to understand the principles and theories behind chiropractic and to apply its techniques properly. Chiropractic provides additional diagnostic and therapeutic means that may help equine practitioners to identify and treat the primary cause of lameness or poor performance. Specialized training in the evaluation and treatment of vertebral joint dysfunction and neuromusculoskeletal disorders places chiropractic in the forefront of conservative treatment of spinal-related disorders. Nevertheless, limited research is currently available on equine chiropractic and other nontraditional modalities in veterinary medicine. In 1996, the American Veterinary Medicine Association's Committee on Alternative and Complementary Therapies suggested that the research community should be encouraged to prioritize avenues of research and to allocate research funds to projects that are designed to provide further scientific evaluation of these modalities. The future of equine chiropractic in veterinary medicine is dependent on future research into the clinical effects of chiropractic techniques and the basic pathophysiology of spinal-related disorders in horses.     

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.     

Alpha-tocopherol protects against oxidative damage to lipids of the rod outer segments of the equine retina

Oxidative stress is a possible risk factor for eye diseases. Lipid peroxidation is one of the major events induced by oxidative stress and is particularly active in polyunsaturated fatty acid (PUFA)-rich biomembranes. This work evaluated endogenous lipid antioxidants, in vitro non-enzymatic lipid peroxidation of rod outer segment membranes (ROS), the fatty acid composition during oxidative damage of total lipids from equine retina and ROS, and the protective action of alpha-tocopherol (alpha-Toc). The major lipid soluble antioxidant was alpha-Toc followed by retinoids and carotenoids. The retina contained a high percentage of PUFAs, mainly docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6). Lipid peroxidation of the equine ROS, induced by Fe(2+)-ascorbate, was monitored using chemiluminescence (CL) with or without pre-treatment with alpha-Toc. With alpha-Toc pre-treatment, CL values were significantly decreased. The most abundant fatty acid was 22:6n-3. After 3h incubation, 95% of total PUFAs were destroyed by peroxidation, whereas in alpha-Toc pre-treated ROS the percentage was significantly decreased. The results show that the retina has an endogenous lipid soluble antioxidant system. ROS were highly sensitive to oxidative damage, since their fatty acid composition was markedly modified during the lipid peroxidation process. The protective role of alpha-Toc as an antioxidant was evident and it could be used in the treatment of equine ocular diseases in which free radicals are involved.     

Diagnosis of Borrelia‐associated uveitis in two horses

Borrelia burgdorferi, the etiologic agent of Lyme disease is a tick born spirochetal infection. Clinical signs of Lyme borreliosis are uncommon in horses, but when present they are often vague and nonspecific. In horses, Lyme borreliosis has been implicated in musculoskeletal, neurological, reproductive, and ocular disorders, including uveitis, but definitive diagnosis can be challenging as the causative agent is rarely isolated and serologic tests can be unreliable and do not confirm active disease. Here, we report two cases of equine uveitis associated with B. burgdorferi based on the identification of spirochetes within ocular fluids and confirmed with PCR testing. The two cases illustrate some of the challenges encountered in the recognition and diagnosis of equine Lyme borreliosis. Although only one of many possible causes of equine uveitis, Lyme disease should be considered a differential diagnosis, especially in endemic areas. Given the possibility for false negative results of serum tests during uveitis associated with B. burgdorferi and the failure of such tests to confirm active infection, a combination of cytologic assessment, antibody, and/or PCR testing of ocular fluids may be worthwhile if the clinical suspicion for Lyme uveitis is high.     

Aqueous humor and plasma concentrations of a compounded 0.2% solution of terbinafine following topical ocular administration to normal equine eyes

Objective To determine the transcorneal penetration and systemic absorption of a compounded 0.2% terbinafine solution following repeated topical administration to normal equine eyes. Sample population Six healthy adult horses with normal ocular examinations. Procedures One eye of each horse received 0.2 mL of a compounded 0.2% terbinafine solution every 4 h for seven doses. During the 1 h following administration of the final dose, multiple peripheral blood samples were obtained, and a single aqueous humor (AH) sample was collected at the end of the hour. AH and plasma concentrations of terbinafine were determined using high pressure liquid chromatography (HPLC). Stability of the formulation was assessed with HPLC analysis over a 14‐day time period. Results Terbinafine was not detected in the AH or plasma of any horse at any time point. No signs of ocular irritation or systemic toxicity were noted in any horse at any time point. The solution was stable over 14 days. Conclusion Topical ocular administration of compounded 0.2% terbinafine solution does not result in detectable AH or plasma levels following administration to normal equine eyes, suggesting its use for deep corneal or intraocular fungal infections in equine ophthalmology may be limited.