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.
Comparison of first, second, and third versus the average of six probe-corneal touches for intraocular measurement of two rebound tonometers in healthy horses. The aim of this study was to evaluate the intraocular pressure (IOP) measurements obtained from first, second, and third probe-cornea touch (PCT) and compare them with the average of six PCTs using two rebound tonometers in horses. This study enrolled a total of thirty-eight stallions, comprising of 24 Arabian horses and 14 cross-breeds (with an average age of 8 ± 3 years). The IOP measurements of first, second, and third, as well as the average of six PCTs were obtained using either Tonovet (TV) or Tonovet Plus (TV+) rebound tonometers. The mean differences (95% limits of agreement) between ...
Extracellular Vesicles Isolated from Equine Adipose-Derived Stromal Stem Cells (ASCs) Mitigate Tunicamycin-Induced ER Stress in Equine Corneal Stromal Stem Cells (CSSCs). Corneal ulcers, characterized by severe inflammation of the cornea, can lead to serious, debilitating complications and may be vision-threatening for horses. In this study, we aimed to investigate the role of endoplasmic reticulum (ER) stress in corneal stem progenitor cell (CSSC) dysfunction and explore the potential of equine adipose-derived stromal stem cell (ASC)-derived extracellular vesicles (EVs) to improve corneal wound healing. We showed that CSSCs expressed high levels of CD44, CD45, and CD90 surface markers, indicating their stemness. Supplementation of the ER-stress-inducer tunicam...
Diamond burr debridement of calcific band keratopathy in 24 eyes of 22 horses. To evaluate the safety and effectiveness of diamond burr debridement (DBD) for the treatment of calcific band keratopathy (CBK) in horses. Methods: Medical records from horses with CBK were reviewed over a period of 4 years. Diagnosis of CBK was based on slit-lamp examination findings, and DBD was performed on standing sedated horses. Follow-up was obtained by clinical reevaluation of the treated eyes or a telephone survey with the referring veterinarian. Results: Twenty-two horses of different ages (median: 11 years; range: 5-23) representing 24 CBK-affected eyes (14 left eyes and 10 righ...
Macrodendritic ulcerative keratitis and conjunctival lymphoid hyperplasia in horses with equine herpesvirus-2 and equine herpesvirus-5 infections. The aim of this study was to describe the clinical, confocal microscopic, histologic, and virologic features of horses with macrodendritic ulcerative keratitis and conjunctival lymphoid hyperplasia associated with equine herpesvirus-2 and equine herpesvirus-5 infection. Methods: Four foals with bilateral ocular disease. Methods: Complete ophthalmic examination was performed for each horse, and corneal samples were collected for cytology and microbiologic evaluation, including virus isolation and molecular diagnostics for the equine herpesviruses. In vivo confocal microscopy examination of the...
Corneal Ulcers in Critically Ill Foals in Intensive Care: Case Series of Standard Treatment and Corneal Cross-Linking. Riboflavin/UV-A corneal cross-linking (CXL) has been applied to treat corneal ulcers in adult horses, but its use in critically ill neonatal foals has not been described. Five cases of hospitalized, critically ill neonatal foals that were in intensive care with corneal ulcers, the ophthalmic treatment, and their outcome up to 1 year are described. A single treatment of CXL phototherapy was performed in three of five foals (five eyes). The application of a riboflavin ophthalmic solution for 20 minutes was followed by the UV-A light irradiation at 30 mW/cm2 for 3 minutes. Topical antibiotic admi...
Topical ropivacaine hydrochloride 0.5% and lidocaine hydrochloride 2% significantly reduce corneal sensitivity without short-term negative side effects in horses. To evaluate corneal sensitivity and acute side effects following application of ropivacaine hydrochloride 0.5% and lidocaine hydrochloride 2% on the healthy equine cornea. Ropivacaine and lidocaine similarly decreased corneal sensitivity when applied topically without clinically evident short-term ocular side effects. Lidocaine may be preferable in clinical settings due to its large, multi-use vials and similar effects to ropivacaine.
Unilateral keratitis secondary to Leishmania spp. infection in a horse: Clinical signs and successful topical therapy. Dermatological clinical signs have been seldom reported in the literature secondary to equine leishmaniasis. This case depicts the clinical signs, treatment, and outcome of a young horse with a pink, elevated lesion on the ventromedial quadrant of the cornea. A corneal cytology was performed and revealed the presence of leishmania amastigotes reaching the diagnosis of keratitis secondary to leishmania. Surgical resection was recommended but the owner declined the procedure, and the lesion was treated with a topical antimonial for 6 weeks. The lesion reduced remarkably during the first weeks ...
Use of Biologics and Stem Cells in Equine Ophthalmology. Regenerative therapy and biologics have the promise to treat equine ocular surface diseases, including corneal ulceration or immune-mediated keratitis, or intraocular diseases such as uveitis. The use of blood-derived products such as serum or platelet-rich plasma, mesenchymal stem cells, or amniotic membrane grafts may be beneficial for the treatment of ulcerative and chronic keratitis in horses. Furthermore, the use of stem cells or gene therapy has promise for the treatment of Intraocular diseases such as equine recurrent uveitis by providing efficacious, practical, and long-term therapy fo...
Ex vivo analysis of ultraviolet radiation transmission through ocular media and retina in select species. The aim of this study was to assess the transmission of the ultraviolet (UV) radiation (200-400 nm) through intact enucleated globes of different species (dogs, cats, pigs, rabbits, horses, and humans) using spectrophotometry. Globes of cats (n = 6), dogs (n = 18), pigs (n = 10), rabbits (n = 6), horses (n = 10), and humans (n = 4) were analyzed. A 5-10 mm circular area of sclera and choroid from the posterior aspect of the globe was removed under a surgical microscope, leaving the retina intact in all species except the horse. Glass coverslips were added in horses and rabbits du...
Effects of subconjunctival ropivacaine, liposomal bupivacaine, and mepivacaine on corneal sensitivity in healthy horses. To evaluate corneal sensitivity and adverse events following subconjunctival administration of three local anesthetics in horses. Methods: Randomized, masked, crossover study. Methods: Twelve healthy adult mares. Methods: The subconjunctival space of the treated eye was injected with 0.2 mL of liposomal bupivacaine (1.3%), ropivacaine (0.5%), or mepivacaine (2%). All horses received each medication once and the contralateral eye received saline (control). Corneal touch threshold (CTT) was measured using a Cochet-Bonnet esthesiometer before sedation, after sedation, and at specified intervals...
Long-term outcome of autologous fascia lata grafting with conjunctival flap overlay in horses with ulcerative keratitis and keratomalacia. To describe the technique, postoperative complications, and outcome after autologous fascia lata grafting with conjunctival flap overlay in horses with ulcerative keratitis and keratomalacia. Methods: Retrospective case series. Methods: Eleven horses with ulcerative keratitis and keratomalacia. Methods: Horses included had undergone fascia lata grafting with conjunctival flap overlay due to impending or recent corneal perforation. Preceding therapy, lesion characteristics, postoperative complications, and short- and long-term outcomes were recorded. Results: Postoperative complications include...
Evaluation of a commercial NGS service for detection of bacterial and fungal pathogens in infectious ulcerative keratitis. To compare results from a commercial next-generation sequencing (NGS) service to corneal cytology and culture for identification of causative organisms in veterinary patients presenting for infectious ulcerative keratitis (IUK). Methods: Swabs for corneal aerobic and fungal cultures and DNA swabs for NGS were submitted for canine and equine normal controls (n = 11 and n = 4, respectively) and IUK patients (n = 22 and n = 8, respectively) for which microbrush cytology specimens confirmed the presence of infectious organisms. The sensitivity of the NGS results was compared with bacterial...
PLDLA/TPU Matrix Enriched with Cyclosporine A as a Therapeutic Platform for Immune-Mediated Keratitis (IMMK) in Horses. The purpose of this study was to describe the use of PLDLA/TPU matrix enriched with cyclosporine A (CsA) as a therapeutic platform in horses with immune-mediated keratitis (IMMK) with an in vitro evaluation CsA release and degradation of the blend as well as determination of the safety and efficacy of that platform used in the animal model. The kinetics of the CsA release from matrices constructed of thermoplastic polyurethane (TPU) polymer and a copolymer of L-lactide with DL-lactide (PLDLA) (80:20) in the TPU (10%) and a PLDL (90%) polymer blend were studied. Moreover, we used the STF (Simul...
Treatment of corneal ulceration and bullous keratopathy using a nictitating membrane flap in two horses. 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. Methods: 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. Methods: A complete ophthalmic examination was performed. Samples were obtained for corneal cytology, and both horses were started on aggres...
Identification of putative orthologs of clinically relevant antimicrobial peptides in the equine ocular surface and amniotic membrane. 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. Methods: 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 wa...
Susceptibility pattern of bacterial isolates in equine ulcerative keratitis: Implications for empirical treatment at a university teaching hospital in Sydney. Corneal ulceration is a common ophthalmic condition in horses. It is frequently caused by trauma to the corneal surface, followed by secondary infection by commensal or pathogenic organisms including Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa and Staphylococcus spp. Emerging antimicrobial resistance amongst these organisms has raised the need for appropriate antimicrobial therapy selection, to optimise treatment efficacy while minimising further antimicrobial resistance. Medical records of 38 horses presented at the University Veterinary Teaching Hospital Camden for ul...
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 examinatio...
Effects of corneoconjunctival transposition, posterior lamellar keratoplasty and modified deep lamellar endothelial keratoplasty on streak retinoscopy in equine cadaver eyes. Evaluate the effects of corneoconjunctival transposition (CCT), posterior lamellar keratoplasty (PLK) and modified deep lamellar endothelial keratoplasty (DLEK) on streak retinoscopy in equine cadaver eyes. Methods: Intraocular pressure (IOP) was maintained at 25 ± 3 mmHg in 35 equine cadaver eyes. Streak retinoscopy was performed prior to (NO VISCO) and following (VISCO) intracameral injection of 1.0 ml of viscoelastic. Following optical coherence tomography (OCT), an axial CCT [n = 11] or PLK [n = 12], or peripheral DLEK [n = 12] was performed. Streak retinoscopy and OCT were r...
Lacrimal Secretion Variation and Menace Response Appearance in Healthy Standardbred Foals From Birth to Four Weeks of Age. This study assesses lacrimal secretion in healthy foals within 48 hours after birth and evaluates their variations in lacrimal secretion and menace response appearance during the first month of life. A total of 31 Standardbred foals were evaluated. Foals were housed with their dams in 4 × 4 m boxes throughout the study. A complete ophthalmic examination was performed for each animal enrolled in the study, including the foals' dams which were used as a control group to compare the lacrimal secretion of foals at birth with that of adult horses. In foals, the Schirmer Tear Test I (STT I) and m...
Morphological, Immunohistochemical, and Ultrastructural Studies of the Donkey’s Eye with Special Reference to the AFGF and ACE Expression. The donkey is mainly used as a working animal for riding and pack transport, as well as for dairy and meat production. Eye afflictions are common in donkeys, thus requiring a detailed study. A few studies had focused on the donkey's eye, and most of them had considered it, merely, a horse's eye. This study aimed to investigate the anatomy, histology, ultrastructure, and immunohistochemical features of the donkey's eye. The results were recorded and compared to those of horses in certain dimensions. Unlike horses, the donkey's eye is more circular in the contour of the cornea, has smaller lenti...
Equine Umbilical Cord Serum Composition and Its Healing Effects in Equine Corneal Ulceration. Human autologous serum (AS) and umbilical cord serum (UCS) both contain growth and neurotrophic factors that promote corneal healing. Unassigned: Our objectives were to compare equine AS and UCS cytokine and growth factor profiles and to assess the safety and clinical feasibility of the therapeutic use of UCS eye drops in cases of spontaneous complex ulcers. Unassigned: Prospective clinical trial. Unassigned: Vitamin A insulin growth factor, platelet-derived growth factor-BB, transforming growth factor (TGF)-β1 (enzyme-linked immunosorbent assay), interleukin (IL)-1β, IL-6, interferon-γ, an...
Immunohistochemical staining of immunoglobulin G in healthy equine, canine, and feline corneas. Establishing an immunohistochemical approach for semi-quantitative assessment of the presence of immunoglobulin G (IgG) in equine, canine, and feline corneas. Methods: Healthy corneas of horses, dogs, and cats, euthanized because of a fatal disease or an unrecoverable trauma unrelated to and without a history of ophthalmic disease were formalin-fixed, paraffin-embedded, and determined to be pathomorphologically healthy by light microscopy. Automated immunohistochemistry was performed using primary antibodies against IgG, biotin-conjugated secondary antibodies, and streptavidin-peroxidase, as w...
Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy. To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry. Methods: Sixty eyes of 30 healthy adult horses aged 8-24 years. Methods: Ultrasonic pachymetry (velocity of 1640 m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50 MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pres...
Therapeutic effects of equine amniotic membrane suspension on corneal re-epithelialization and haze in a modified lagomorph ex vivo wound healing model. To investigate the therapeutic effects of topical equine amniotic membrane (eAM) suspension following corneal wounding in a controlled experimental setting. Methods: Equine amniotic membrane was collected, gamma irradiated, homogenized for topical suspension preparation, and cryopreserved. Corneoscleral rims harvested from fresh rabbit globes were wounded via keratectomy and were maintained in an air-liquid interface ex vivo corneal culture model. Treatment groups included topical gamma irradiated eAM suspension (n = 20) and a control group (n = 20). Re-epithelialization of the wound was a...
Comparison of image quality of corneal and retinal optical coherence tomography using sedation and general anesthesia protocols with or without retrobulbar anesthesia in horses. To compare image quality and acquisition time of corneal and retinal spectral domain optical coherence tomography (SD-OCT) under 3 different sedation-anesthesia conditions in horses. Methods: 6 middle-aged geldings free of ocular disease. Methods: 1 randomly selected eye of each horse was evaluated via SD-OCT under the following 3 conditions: standing sedation without retrobulbar anesthetic block (RB), standing sedation with RB, and general anesthesia with RB. Five regions of interest were evaluated in the cornea (axial and 12, 3, 6, and 9 o'clock positions) and fundus (optic nerve head). Thre...
Interleukin-6 and lactate dehydrogenase expression in a novel ex vivo rocking model of equine corneal epithelial wound healing. To establish a physiologically relevant ex vivo model of equine corneal epithelial wound healing. Methods: Fourteen equine corneas were randomly assigned to one of two groups: wounded (n = 8) or unwounded (n = 6) controls. In the wounded group, the axial corneal epithelium was removed by applying a 6 mm filter paper disk soaked in 1N-NaOH for 60 s. Corneas were subsequently cultured using an air-liquid interface model. Evaluation of corneal healing was performed daily, and culture medium was collected. Corneas were randomly assigned to undergo processing via histopathology and RNAscope i...
Evaluation of equine corneal disease using ultrasound biomicroscopy. To describe the clinical use of ultrasound biomicroscopy (UBM) to evaluate equine corneal disease. Methods: Images were obtained using a 50-MHz probe ultrasound biomicroscopy system (Quantel Aviso) and Clear Scan® probe cover. Six horses with corneal disease were evaluated via UBM for lesion size, lesion depth, and continuity of Descemet's membrane. Horses were sedated and received auriculopalpebral nerve blocks and application of topical anesthetic prior to UBM. Results: Ultrasound biomicroscopy was easily performed in all cases. UBM evaluation of three cases of corneo-limbal squamous cell c...