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.
High resolution imaging of the equine cornea using the DUB®-SkinScanner v3.9. The aim was to describe the use of the DUB®-SkinScanner v3.9 (taberna pro medicum GmbH, Lueneburg, Germany) for the examination of the equine cornea. Methods: Using the DUB®-SkinScanner v3.9 various pathological corneal conditions were pictured in the A- and B-mode at a frequency of 22 and/or 50 MHz in nine eyes of eight horses. Scans were obtained from standing horses or from horses under general anesthesia non-related to image acquisition. Results: The examination allowed real time imaging and measurement of the equine cornea in vivo. Compared to slit-lamp biomicroscopy additional informa...
Comparison of the in vitro anticollagenase efficacy of homologous serum and plasma on degradation of corneas of cats, dogs, and horses. OBJECTIVE To compare the anticollagenase efficacy of fresh feline, canine, and equine serum and plasma on in vitro corneal degradation. SAMPLE Grossly normal corneas from recently euthanized dogs, cats, and horses and fresh serum and plasma from healthy dogs, cats, and horses. PROCEDURES Serum and plasma were pooled by species and used for in vitro experiments. Corneas were collected and stored at -80°C. Sections of cornea were dried, weighed, and incubated in saline (0.9% NaCl) solution with clostridial collagenase and homologous fresh serum or plasma. Corneal degradation was assessed as the...
Glaucoma with Descemet’s membrane detachment in five horses. To describe the clinical and histopathologic features of glaucoma associated with Descemet's membrane (DM) detachment in five horses without prior history of intraocular surgery. Methods: Three Appaloosa horses and two Thoroughbreds were included in this study. The affected horses ranged in age from 16 to 27 years and presented with severe diffuse corneal edema. Methods: Five eyes were enucleated due to intraocular hypertension and/or chronic corneal ulceration. The enucleated globes were evaluated by the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW). Each globe was routinely ...
Modified penetrating keratoplasty with Acell® bioscaffold implant in seven horses with deep full-thickness corneal stromal abscess. To describe and evaluate a modified penetrating keratoplasty technique utilizing ACell® for management of equine deep stromal or full-thickness corneal stromal abscesses (SA). Methods: Cases presenting to the University of Georgia Ophthalmology service for surgical management of SA necessitating penetrating keratoplasty (PK) were included in the study population. Surgery entailed the use of an ACell® disk sutured within the deep level of a stepped full-thickness corneal incision with an overlying conjunctival pedicle flap placed in the superficial step incision. Patients were evaluated for s...
Corneal edema in four horses treated with a superficial keratectomy and Gundersen inlay flap. To describe the clinical presentation, treatment, and outcome of four horses with severe corneal edema caused by suspected endothelial disease treated with a superficial keratectomy and Gundersen inlay flap and to determine whether this procedure (i) reduces corneal edema, (ii) reduces ocular pain, (iii) eliminates recurrent corneal ulceration, and (iv) improves vision in these horses. Methods: Four horses met inclusion criterion of (i) diagnosis with endothelial disease by a board-certified veterinary ophthalmologist and (ii) surgical treatment with a superficial keratectomy and Gundersen inl...
Comparison of corneal degeneration and calcific band keratopathy from 2000 to 2013 in 69 horses. To compare signalment, presentation, treatment, and outcome in horses diagnosed with corneal degeneration (CD) or calcific band keratopathy (CBK) at a referral hospital. Methods: Sixty-nine horses (87 eyes) diagnosed with either CD or CBK. Methods: Medical records of horses diagnosed with CD or CBK at the University of California-Davis Veterinary Medical Teaching Hospital (UCD-VMTH) between 2000 and 2013 were reviewed. Signalment, concurrent ophthalmic diagnoses, previous therapies, diagnostic tests, systemic diagnoses, treatment, follow-up, and outcomes were compared between horses diagnosed ...
Evaluation of species differences and the effects of storage duration and temperature on the anticollagenase efficacy of canine, feline, and equine serum on in vitro corneal degradation. OBJECTIVE To evaluate species differences and effects of storage duration and temperature on the anticollagenase efficacy of canine, feline, and equine serum on in vitro corneal degradation. SAMPLES Corneas and serum from dogs, cats, and horses. PROCEDURES Clinically normal corneas from dogs, cats, and horses were harvested within 2 hours after euthanasia. Serum samples from dogs, cats, and horses were collected and pooled by species. Corneal specimens were incubated with collagenase derived from Clostridium histolyticum, 5mM calcium chloride in saline (0.9% NaCl) solution, and feline, canine,...
Penetration depth of corneal cross-linking with riboflavin and UV-A (CXL) in horses and rabbits. CXL penetration depth is an important variable influencing clinical treatment effect and safety. The purposes of this study were to determine the penetration depth of CXL in rabbit and equine corneas in epithelium-on and epithelium-off procedures and to assess an ex vivo fluorescent biomarker staining assay for objective assessment of CXL penetration depth. Methods: CXL treatment was performed according to a standardized protocol on 21 and 17 rabbit eyes and on 12 and 10 equine eyes with and without debridement, respectively. Control corneas were treated similarly, but not exposed to CXL. Hem...
Comparative morphological evaluation of domestic animal cornea. This study described corneal morphology in different domestic animals using histological and immunohistochemical methods. Specifically, we evaluated the species-specific distribution pattern of cytokeratins (CKs) and aquaporins (AQPs) to assess their contribution to the strength and transparency of the cornea, respectively. Methods: Corneal sections (2 μm thick) were obtained from 28 pigs, 11 cows, two goats, six horses, four dogs, and five cats and stained with hematoxylin-eosin and periodic acid-Schiff (PAS) reaction. Immunohistochemistry was also performed using CK1 to 3 and AQP1 and 5 an...
Suspected malignant transformation of B lymphocytes in the equine cornea from immune-mediated keratitis. To describe clinical, in vivo confocal microscopic, histopathologic, polymerase chain reaction assay for antigen receptor rearrangement (PARR) and immunohistochemical features of a horse with suspected malignant transformation of corneal B lymphocytes in immune-mediated keratitis (IMMK) and to also report surgical management and adjunctive treatment including topical and radiation therapies. Methods: A 15-year-old Oldenburg gelding was examined for presumptive progressive stromal IMMK of the right eye which became refractory to medical management. Corneal in vivo confocal microscopy revealed...
Central corneal thickness measurements and ultrasonographic study of the growing equine eye. The aim of this study was to determine the central corneal thickness (CCT) of healthy equine eyes with high-frequency ultrasound (HF) and ultrasound biomicroscopy (UBM) and to measure the axial dimensions with B-mode ultrasound. Additionally, the influence of the age on the measured dimensions of the globe was analyzed. Methods: Fifty warm blood horses (mean age 23.0 ± 21.12 months) were divided into 3 age groups (group 1: 0-6 months; group 2: ≥7-30 months; and group 3: ≥31-78 months). Methods: Corneal measurements were performed with a 22-MHz and a 50-MHz transducer. Crystalline lens thi...
Detection of equine herpesvirus in horses with idiopathic keratoconjunctivitis and comparison of three sampling techniques. To determine the role of equine herpesvirus (EHV) in idiopathic keratoconjunctivitis in horses and to determine whether sample collection method affects detection of EHV DNA by quantitative polymerase chain reaction (qPCR). Methods: Twelve horses with idiopathic keratoconjunctivitis and six horses without signs of ophthalmic disease. Methods: Conjunctival swabs, corneal scrapings, and conjunctival biopsies were collected from 18 horses: 12 clinical cases with idiopathic keratoconjunctivitis and six euthanized controls. In horses with both eyes involved, the samples were taken from the eye judg...
Unilateral choristoma of the nictitating membrane in a horse. A 2-year-old Morgan mare was evaluated because of a corneal ulceration. Results: An irregular, deep stromal corneal ulcer in an area of malacia was noted in the left eye. Hypopyon was present in the ventral portion of the anterior chamber with moderate aqueous flare. The nictitating membrane of the left eye had hairs originating from its leading edge that contacted the corneal surface. Results: General anesthesia was induced, and a bulbar pedicle conjunctival graft was performed. The conjunctiva at the leading edge of the nictitating membrane, including the aberrant hair follicles, was excised...
Porcine urinary bladder extracellular matrix grafts (ACell Vet® Corneal Discs) for keratomalacia in 17 equids (2012-2013). To describe the clinical course, outcomes, and complications associated with use of commercially available porcine urinary bladder extracellular matrix (ECM) grafts (ACell Vet(®) Corneal Discs) in equid patients with keratomalacia, and to evaluate the efficacy of ECM grafts as a viable alternative to other biomaterials for corneal grafting in equid patients. Methods: Sixteen horses and one donkey (17 eyes) with unilateral keratomalacia severe enough to warrant surgical repair between August 2012 and September 2013. Methods: Retrospective medical record review to identify equid patients meetin...
Ocular dimensions, corneal thickness, and corneal curvature in quarter horses with hereditary equine regional dermal asthenia. The aim of this study was to compare ocular dimensions, corneal curvature, and corneal thickness between horses affected with hereditary equine regional dermal asthenia (HERDA) and unaffected horses. Methods: Five HERDA-affected quarter horses and five healthy control quarter horses were used. Methods: Schirmer's tear test, tonometry, and corneal diameter measurements were performed in both eyes of all horses prior to ophthalmologic examinations. Ultrasonic pachymetry was performed to measure the central, temporal, nasal, dorsal, and ventral corneal thicknesses in all horses. B-mode ultrasound...
Modified lamellar keratoplasties for the treatment of deep stromal abscesses in horses. To describe a surgical modification of deep lamellar endothelial keratoplasty (DLEK) and posterior lamellar keratoplasty (PLK) procedures, to facilitate surgery on standing horses under-sedation. Methods: Four client-owned horses, for which the owners declined surgery under general anesthesia, underwent standing corneal lamellar keratoplasty procedures for the treatment of deep corneal stromal abscesses. Methods: All four horses were placed in stocks and sedated with detomidine. Local eyelid and retrobulbar blocks were performed to provide local analgesia and akinesia, and each horse's head wa...
Descemet’s membrane detachment in horses; case series and literature review. The aim of this article was to describe Descemet's membrane detachment (DMD) following phacoemulsification in five equine eyes and to review the human literature on this topic. In the last decade, there has been increased reporting of DMD in the human literature, in particular following cataract surgery. The natural history of DMD remains unknown and although various medical and surgical treatments have been advocated there is no recognized 'gold standard' treatment for DMD. This case series reports the diagnosis of DMD in four horses (5 eyes) in association with phacoemulsification surgery. T...
Nasal and ocular amyloidosis in a 15-year-old horse. Localized nasal, conjunctival and corneal amyloidosis was diagnosed in a 15-year-old pony with nasal and conjunctival masses and severe dyspnoea. Multiple swellings had been evident in the nostrils for at least two years and had gradually increased in size before presentation due to dyspnoea and exercise intolerance. Surgical debulking of the masses was performed and histological examination revealed large amounts of extracellular, hyaline, eosinophilic, Congo red positive material in the lamina propria of the nasal mucosa. A tentative diagnosis of localized nasal amyloidosis was made. The tre...
Suberoylanilide hydroxamic acid (vorinostat): its role on equine corneal fibrosis and matrix metalloproteinase activity. To explore the effect of suberoylanilide hydroxamic acid (SAHA) (i) on corneal fibroblast differentiation, morphology, and viability; and (ii) on the expression levels of matrix metalloproteinases (MMPs) 2 and 9 using an in vitro model of equine corneal fibrosis. Methods: Healthy donor corneas were used to generate primary cultures of equine corneal fibroblasts. The fibroblasts were exposed to 5 ng/mL TGFβ1 to induce myofibroblast formation. The cultures were treated with either 5 μm or 10 μm SAHA for 72 h in the presence of TGFβ1. Real-time PCR and immunocytochemistry were used to determi...
Histopathological features of equine superficial, nonhealing, corneal ulcers. To evaluate corneal changes associated with chronic, nonhealing, superficial, corneal ulcers in horses via common histopathological stains. Methods: Retrospective study. Methods: Twenty-four horses diagnosed with chronic, nonhealing, superficial, corneal ulceration. Methods: The medical records of horses evaluated at North Carolina State University's Veterinary Teaching Hospital (NCSU-VTH) from 2005 to 2011, diagnosed with a chronic, nonhealing, superficial, corneal ulcer and treated with superficial keratectomy (SK) were reviewed. Inclusion criteria were superficial corneal ulceration, no cel...
Therapeutic potential of Pirfenidone for treating equine corneal scarring. To evaluate the safety and efficacy of Pirfenidone (PFD) in the treatment of equine corneal fibrosis using an in vitro model. Methods: Healthy donor equine corneas were collected and used to generate primary equine corneal fibroblasts (ECFs) by growing cultures in minimal essential medium supplemented with 10% fetal bovine serum. Equine corneal myofibroblasts (ECMs), used as a model of equine corneal fibrosis, were produced by growing ECF cultures in serum-free medium containing transforming growth factor β1 (1 ng/mL). Trypan blue viability assays and changes in ECF morphology were utilized t...
Spectral-domain optical coherence tomography evaluation of the cornea, retina, and optic nerve in normal horses. To determine the feasibility of using a handheld spectral-domain optical coherence tomography (SD-OCT) instrument to characterize normal corneal, retinal, and optic nerve head anatomy in vivo in standing horses. Methods: Clinically normal horses under sedation, palpebral nerve blockage, and pharmacologically induced mydriasis were imaged with a SD-OCT instrument (Envisu SD-OCT, Bioptigen, Inc., Morrisville, NC). Radial volumes from the cornea (axial, superior, inferior, nasal, and temporal), and rectangular volumes from the retina (dorsal, ventral, nasal, and temporal) and optic nerve head wer...
Corneal dystrophy in Friesian horses may represent a variant of pellucid marginal degeneration. To describe the clinical presentation, treatment, and outcome of a corneal dystrophy in Friesian horses and to analyze affected horses' pedigrees to investigate its heritability. Methods: Nine Friesians with bilateral disease were identified. Methods: Retrospective medical record review was used to identify Friesian horses exhibiting bilateral symmetric corneal lesions. Variables identified from medical records included patient sex and age at diagnosis; location, depth and size of corneal lesions; medical and surgical therapy instituted; and visual outcome. A four-generation pedigree for each ...
Treatment of nonhealing corneal ulcers in 60 horses with diamond burr debridement (2010-2013). To review the signalment, clinical characteristics, and outcome of horses with nonhealing corneal ulcers treated with diamond burr debridement (DBD); and to evaluate the role of ulcer duration, size and location, and bandage contact lens (BCL) placement on healing. Methods: From January 2012-April 2013, 60 horses were diagnosed with ulcers classified as nonhealing based on the presence of raised epithelial margins and duration of at least 7 days. Methods: Retrospective record review. Results: Average age of included horses was 14.68 years, SD 8.17 years. There were three times as many males (4...
Comparative evaluation of aqueous humor viscosity. To evaluate aqueous humor viscosity in the raptor, dog, cat, and horse, with a primary focus on the barred owl (Strix varia). Methods: Twenty-six raptors, ten dogs, three cats, and one horse. Methods: Animals were euthanized for reasons unrelated to this study. Immediately, after horizontal and vertical corneal dimensions were measured, and anterior chamber paracentesis was performed to quantify anterior chamber volume and obtain aqueous humor samples for viscosity analysis. Dynamic aqueous humor viscosity was measured using a dynamic shear rheometer (AR 1000 TA Instruments, New Castle, DE, US...
In vivo confocal microscopy of corneal microscopic foreign bodies in horses. To describe in vivo corneal confocal microscopy of horses with microscopic corneal foreign bodies and to correlate findings with clinical, cytological, and histopathologic evaluations of clinical cases and foreign body morphologies observed in vitro with the confocal microscope. Methods: Five horses with microscopic corneal foreign bodies. Methods: Sedated and anesthetized horses were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module. Confocal microscopy images were compared with images from cytologic and histopathologic corneal samples. To establish microscopic...
Manual corneal thickness measurements of healthy equine eyes using a portable spectral-domain optical coherence tomography device. Corneal thickness measurements of the equine globe using spectral-domain optical coherence tomography (SD-OCT) have not been reported. Objective: To determine corneal thickness measurements and the intra- and interoperator reliability of a portable SD-OCT device in equine eyes. Methods: Prospective observational study. Methods: Horses free of ocular disease were used for this study. Gentle manual restraint, in combination with detomidine hydrochloride and a head stand, were employed to ensure proper animal positioning. Corneal pachymetry measurements were obtained from both eyes of each animal...
Mast cell tumor invading the cornea in a horse. A 3-year-old Marwari mare was presented for evaluation of an irregular, reddish mass protruding from behind the right third eyelid. The mass appeared to arise at the ventral limbal area, involved the perilimbal bulbar conjunctiva and widely extended into corneal tissue. No other ocular or systemic abnormalities were detected at the time of presentation. The mass was surgically removed by lamellar keratectomy, with defocused CO(2) laser used as adjunctive therapy to treat the surgical exposed area and its surroundings. Histopathologic evaluation showed sheets of densely packed, well-differentia...
Evaluation of the effects of age and pituitary pars intermedia dysfunction on corneal sensitivity in horses. To determine effects of age and pituitary pars intermedia dysfunction (PPID) on corneal sensitivity in horses. Methods: 20 adult horses allocated into 3 groups (PPID group, old [> 15 years old] horses with PPID [n = 5]; old group, old [> 15 years old] horses without PPID [9]; and young group, young [≤ 10 years old] horses without PPID [6]). All horses with PPID had hirsutism and abnormal fat deposition or laminitis; none of the old or young horses had hirsutism, abnormal fat deposition, or laminitis. Methods: A Cochet-Bonnet aesthesiometer was used to measure the corneal touch threshold (CTT...