Topic:Cornea
The cornea in horses is a transparent, dome-shaped surface that covers the front of the eye, playing a vital role in focusing vision. It serves as a barrier against pathogens and physical damage while maintaining ocular hydration and transparency. The equine cornea is composed of several layers: the epithelium, stroma, Descemet's membrane, and endothelium, each contributing to its overall function and health. Conditions affecting the cornea, such as ulcers, infections, and trauma, are common in horses and can significantly impact visual acuity and comfort. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathology, and treatment of corneal conditions in horses.
Solitary (primary) uveal T-cell lymphoma in a horse. A 22-year-old Australian stockhorse gelding was presented with anterior uveitis in the right eye which was nonresponsive to anti-inflammatory therapy. Clinical examination revealed corneal edema and vascularization, marked hypopyon, and thickening of the dorsal iris, which was confirmed by ultrasonography. Hematologic and biochemical analyses, abdominal and thoracic ultrasonography, and abdominocentesis with cytologic and biochemical analysis revealed no significant abnormalities. Cytological examination of an aqueous humor sample revealed a population of predominantly large lymphoblasts with ...
Corneal cross-linking in 9 horses with ulcerative keratitis. Corneal ulcers are one of the most common eye problems in the horse and can cause varying degrees of visual impairment. Secondary infection and protease activity causing melting of the corneal stroma are always concerns in patients with corneal ulcers. Corneal collagen cross-linking (CXL), induced by illumination of the corneal stroma with ultraviolet light (UVA) after instillation of riboflavin (vitamin B2) eye drops, introduces crosslinks which stabilize melting corneas, and has been used to successfully treat infectious ulcerative keratitis in human patients. Therefore we decided to study i...
Decorin-PEI nanoconstruct attenuates equine corneal fibroblast differentiation. To explore (i) the potential of polyethylenimine (PEI) nanoparticles as a vector for delivering genes into equine corneal fibroblasts (ECFs) using green fluorescent protein (GFP) marker gene, (ii) whether PEI nanoparticle-mediated decorin (DCN) gene therapy could be used to inhibit fibrosis in the equine cornea using an in vitro model. Methods: Polyethylenimine-DNA nanoparticles were prepared at nitrogen-to-phosphate (N-P) ratio of 15 by mixing 22 kDa linear PEI and a plasmid encoding either GFP or DCN. ECFs were generated from donor corneas as previously described. Initially, GFP was introduc...
Anatomical location and culture of equine corneal epithelial stem cells. To identify morphologically the locations of equine corneal epithelial stem cells (CESCs) and to culture these cells. Methods: We studied the eyes of 12 adult thoroughbred horses. Methods: Eye tissues were immunostained for two positive stem cell markers (p63, CK14) and one negative marker (CK3) to identify the locations of CESCs, so we could compare their immunostaining patterns with those of human stem cells previously reported. We compared the proliferation rates and morphological features of epithelial cells isolated from the corneal limbus and central cornea. Results: Undifferentiated cel...
Penetrating keratoplasty and graft rejection in eight horses. The aim of this study was to describe long-term follow-up and difference in immune reactions in the tear film following penetrating keratoplasty (PK) in horses when differently preserved corneas were utilised. This report describes for the first time the use of corneal grafts preserved in tissue culture media in equine PK. Eight experimental horses with normal eyes were included and freshly harvested, frozen or preserved corneal grafts were used for the PK. The graft-taking technique and storage, PK surgery, postoperative treatments and complications are described. The mean postoperative follo...
Corneal ulcers in horses. Corneal ulceration is commonly diagnosed by equine veterinarians. A complete ophthalmic examination as well as fluorescein staining, corneal cytology, and corneal bacterial (aerobic) and fungal culture and sensitivity testing are necessary for all infected corneal ulcers. Appropriate topical antibiotics, topical atropine, and systemic NSAIDs are indicated for all corneal ulcers. If keratomalacia (melting) is observed, anticollagenase/antiprotease therapy, such as autologous serum, is indicated. If fungal infection is suspected, antifungal therapy is a necessity. Subpalpebral lavage systems all...
Visual outcome after corneal transplantation for corneal perforation and iris prolapse in 37 horses: 1998-2010. We wanted to investigate the visual outcome of horses presented with iris prolapse and treated with corneal transplantation. Objective: To evaluate the visual outcome of horses with iris prolapse treated with penetrating keratoplasty alone and penetrating keratoplasty in combination with overlying conjunctival or amniotic membrane grafting. Methods: A retrospective medical records study of horses presented to the University of Florida Veterinary Medical Center for iris prolapse and treated with penetrating keratoplasty in the period of 1998-2010. Data collected from the medical records include...
Comparison of efficacy and duration of effect on corneal sensitivity among anesthetic agents following ocular administration in clinically normal horses. To compare efficacy and duration of effect on corneal sensitivity of 0.5% proparacaine hydrochloride, 0.5% bupivacaine hydrochloride, 2% lidocaine hydrochloride, and 2% mepivacaine hydrochloride solutions following ocular administration in clinically normal horses. Methods: 68 clinically normal horses. Methods: 60 horses were assigned to receive 1 anesthetic agent in 1 eye. For each of another 8 horses, 1 eye was treated with each of the anesthetic agents in random order with a 1-week washout period between treatments. Corneal sensitivity was assessed via corneal touch threshold (CTT) measurem...
Corneal stromal abscessation in two horses treated with intracorneal and subconjunctival injection of 1% voriconazole solution. To describe and evaluate intrastromal and subconjunctival injection of voriconazole for the therapy of deep corneal stromal abscess (DSA) in horses. Methods: A retrospective clinical study describing the indications for intrastromal and subconjunctival voriconazole injection and the outcomes of this procedure in two eyes of two horses. Methods: The two horses in this study failed to respond to medical therapy. Treatment with intracorneal and subconjunctival administration of 1% voriconazole was performed in this study. Results: Treatment with intracorneal and subconjunctival administration of ...
Fungal polymerase chain reaction testing in equine ulcerative keratitis. To assess the diagnostic utility of fungal polymerase chain reaction (PCR) in forty-three horses with naturally acquired corneal ulcers presenting to a private practice. Methods: Routine evaluation of cytologic, histologic, and microbiologic samples was performed. Two PCR approaches were compared - generic and specific fungal nested PCR followed by sequencing and quantitative PCR (qPCR). PCRs were applied to pure control fungal cultures, corneal tissue from ulcerated eyes and in a subset of 9 horses, to swabs from contralateral normal eyes. Results: The expected fungus was identified by nested...
Association of height, body weight, age, and corneal diameter with calculated intraocular lens strength of adult horses. To determine whether differences exist in the calculated intraocular lens (IOL) strengths of a population of adult horses and to assess the association between calculated IOL strength and horse height, body weight, and age, and between calculated IOL strength and corneal diameter. Methods: 28 clinically normal adult horses (56 eyes). Methods: Axial globe lengths and anterior chamber depths were measured ultrasonographically. Corneal curvatures were determined with a modified photokeratometer and brightness-mode ultrasonographic images. Data were used in the Binkhorst equation to calculate the ...
Multicentric T-cell lymphoma presenting as inferior palpebral swelling in a Standardbred mare. A 6-year-old Standardbred mare that presented with bilateral palpebral swelling and a left corneal ulcer was diagnosed with a multicentric T-cell lymphoma. Other clinical findings included submandibular lymphadenopathy and oedema, pharyngeal oedema and rhinitis. Prior to euthanasia the horse developed keratomalacia, the onset of which was coincidental with the use of high doses of topical and systemic corticosteroids. Although an unusual presentation, palpebral swelling should be considered as a clinical sign of lymphoma.
Correlation between corneal sensitivity and quantity of reflex tearing in cows, horses, goats, sheep, dogs, cats, rabbits, and guinea pigs. Guinea pigs have a very low threshold of corneal sensitivity and at the same time nearly no reflex tearing compared to dogs, cats, and horses. The question arose whether there is a general correlation between corneal sensitivity and the quantity of reflex tearing. Methods: Totally 160 animals of 8 different species (20 animals per species) were investigated. Methods: The corneal touch threshold (CTT) was measured with a Cochet-Bonnet esthesiometer. The palpebral fissure length (PFL) was measured with a calliper ruler. The Schirmer tear test (STT) was modified by adapting the width of the STT s...
Ophthalmological findings in a closed herd of Lipizzaners. There are no studies on the ophthalmic health status in the Lipizzaner breed. Objective: To perform an ophthalmological survey in a closed herd in 3 housing systems. Methods: All horses at the Federal Stud Piber, Heldenberg and the Spanish Riding School Vienna were subjected to ophthalmological examination. Findings were documented and correlated with factors such as age, gender, location and housing situation. The interrelation of abnormalities of different regions was determined by calculating accuracy. Pedigree analysis of horses affected by cataract was performed. Results: A total of 267 h...
Equine keratomycoses in California from 1987 to 2010 (47 cases). Equine keratomycosis in the western USA has received little study, probably owing to its low prevalence. Objective: To determine clinical features, predominant fungal isolates, treatment modalities and outcomes of horses with keratomycosis in California and compare these with results from different geographic regions. Methods: Records of horses presented to the University of California-Davis Veterinary Medical Teaching Hospital (UCD-VMTH) with confirmed keratomycosis between 1987 and 2010 were reviewed for this retrospective study. Information retrieved from the record included background, oph...
A pilot study on the corneal curvatures and ocular dimensions of horses less than one year of age. Intraocular lenses (IOLs) have been implanted in adult equine eyes after cataract surgery. Foals and weanlings comprise a large proportion of those horses undergoing cataract surgery. Due to potential differences in the size and corneal curvature of the juvenile eye, it is not currently known whether implantation of adult IOLs is appropriate in foals and weanlings. The objective of the study was to measure the anterior chamber depth (ACD), central lens thickness (CLT), vitreous chamber depth (VCD), axial globe length (AGL) and corneal curvature of horses less than one year of age. The axial di...
Immunohistochemical and immunopathologic characterization of superficial stromal immune-mediated keratitis in horses. To describe the immunopathologic characteristics of superficial stromal immune-mediated keratitis (IMMK) immunopathologically by characterizing cellular infiltrate in affected corneas of horses. Methods: 10 client-owned horses with IMMK. Methods: Immunohistochemical staining was performed on keratectomy samples with equine antibodies against the T-cell marker CD3 and B-cell marker CD79a (10 eyes) and the T-helper cytotoxic marker CD4 and T-cell cytotoxic marker CD8 (6 eyes). Percentage of positively stained cells was scored on a scale from 0 (no cells stained) to 4 (> 75% of cells stained)....
An ex vivo model for suture-less amniotic membrane transplantation with a chemically defined bioadhesive. Chemically defined bioadhesives (CDB) are "two-component reactive adhesives" made from antibiotic food additives. They contain no animal-derived ingredients and are characterized by a high level of self-degradability, low toxicity, and strong bonding properties. Amniotic membrane (AM) transplantation is used to repair severe ocular surface disease in humans and horses. AM requires meticulous suturing to the injured cornea. The purpose of this study is to determine whether CDB can facilitate the suture-less placement and adherence of equine AM to porcine cadaver cornea. Methods: Prospective stu...
Optimal management of equine keratomycosis. Keratomycosis in the horse exists in several unique clinical forms. This paper discusses the diagnosis and clinical management of keratomycosis in the horse associated with tear film instability, epithelial keratopathy, subepithelial infiltrates, superficial and deep ulcers, plaques, melting ulcers, descemetoceles, iris prolapse, and stromal abscesses. Prompt diagnosis and aggressive treatment of equine keratomycosis can make a major difference in the maintenance of a cosmetic and visual eye.
Third eyelid dermoid in a horse. An 8-year-old Gypsy Vanner gelding presented to the University of Florida Ophthalmology service for the evaluation of chronic, recurrent corneal ulcers behind the third eyelid of the right eye. On ophthalmic examination, a cluster of aberrant hairs was identified growing along the margin of the third eyelid. This portion of third eyelid was surgically excised, and histopathology identified the haired tissue as a dermoid. Chronic keratitis secondary to a third eyelid dermoid was diagnosed, and excision appeared curative at 6 months post-operative follow-up.
Ocular lesions following suspected lightning injury in a horse.   To describe the gross and histopathological ocular findings in a horse following suspected lightning injury. Methods:   The eyes of a 2-year-old thoroughbred gelding were clinically and histopathologically evaluated following a severe lightning storm following euthanasia because of visual impairment. Results:   Severe corneal edema and hydrops were noted clinically oculus dexter. Indirect ophthalmoscopy revealed bilateral symmetrical raised hyporeflective peripapillary geographic lesions. Histopathologic evaluation revealed corneal edema in the right eye with normal corneal endothelium...
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...
Conjunctival bacterial and fungal flora in healthy horses in the UK. To describe the bacterial and fungal flora of the normal conjunctiva of horses in the UK; to determine the effect of horse age, sex, geographic location, and housing on this flora; and to determine the most appropriate antimicrobial drug(s) for prophylactic treatment of corneal ulcers. Methods: A total of 60 adult healthy horses were studied. Methods: Swabs of the conjunctiva were obtained from 60 horses housed in two locations within the UK. Specimens were cultured for aerobic bacteria and fungi, and sensitivity against six ophthalmic antimicrobials assessed. The effect of age, sex, location ...
A survey of ocular abnormalities in miniature horses. To determine the incidence of ocular abnormalities in miniature horses. Methods: Descriptive study. Methods: Fifty-three miniature horses. Methods: Ophthalmic examinations were performed using diffuse and focal illumination, slit-lamp biomicroscopy and indirect ophthalmoscopy. Coat color, mane and tail color, age and gender were recorded with results of ophthalmic examination. Results: Ocular abnormalities detected most frequently consisted of cysts arising from the posterior iris, ciliary body, and peripheral retina, curvilinear streaks of retinal pigmented epithelium extending from the perip...
Expression of Toll-like receptors 2, 3, 4, 6, 9, and MD-2 in the normal equine cornea, limbus, and conjunctiva. Human corneal cells have detectable levels of TLRs 1-10. TLRs 2 and 4 are the major corneal receptors, recognizing the PAMPs associated with fungal invasion in humans. The conjunctiva and limbus contain TLRs 2, 4, and 9. Our purpose was to determine the expression of TLRs 2, 3, 4, 6, 9, and MD-2 in the normal equine cornea, conjunctiva, and limbus. Methods: Corneal, limbal, and conjunctival tissues were collected from seven euthanized horses having no evidence of ocular disease. RNA extraction with DNase-1 digestion was performed followed by RT-PCR to determine expression of TLRs 2, 3, 4, 6, 9...
Tear, cornea, and aqueous humor concentrations of ciprofloxacin and moxifloxacin after topical ocular application in ophthalmologically normal horses. To determine ocular tissue drug concentrations after topical ocular administration of 0.3% ciprofloxacin and 0.5% moxifloxacin in ophthalmologically normal horses. Methods: 24 ophthalmologically normal adult horses. Methods: 0.3% ciprofloxacin and 0.5% moxifloxacin solutions (0.1 mL) were applied to the ventral conjunctival fornix of 1 eye in each horse as follows: group 1 (n = 8) at 0, 2, 4, and 6 hours; group 2 (8) at 0, 2, 4, 6, and 10 hours; and group 3 (8) at 0, 2, 4, 6, 10, and 14 hours. Tears, cornea, and aqueous humor (AH) were collected at 8, 14, and 18 hours for groups 1, 2, and 3, r...
In vivo confocal microscopy of equine fungal keratitis. To describe in vivo corneal confocal microscopy of horses with fungal keratitis and correlate findings with clinical, histopathological, and microbiological evaluations of clinical cases and an ex vivo experimental equine fungal keratitis model. Methods: A total of 12 horses with naturally-acquired fungal keratitis and ex vivo equine corneas experimentally infected with clinical fungal isolates. Methods: Horses with naturally-acquired fungal keratitis were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module. Confocal microscopy images of clinical isolates of Asper...