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Topic:Ophthalmology
Ophthalmology in horses encompasses the study and treatment of eye disorders and diseases affecting equine species. Equine ophthalmic conditions can range from conjunctivitis and corneal ulcers to more complex issues such as uveitis and cataracts. These conditions can impact a horse's vision and overall well-being. Diagnostic techniques in equine ophthalmology include visual examinations, fluorescein staining, and advanced imaging methods like ultrasonography. Treatment approaches vary depending on the specific condition and may involve medication, surgical intervention, or supportive care. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, pathology, diagnostics, and treatment modalities related to equine ophthalmology.
Mesenchymal stem cells in veterinary clinical practice: Evidence from naturally occurring diseases. Over the past two decades, the use of mesenchymal stem cells (MSCs) in veterinary medicine has expanded rapidly, although the clinical evidence remains in its early stages. This review discusses clinical studies involving client-owned animals with naturally occurring diseases in which MSCs or MSC-derived extracellular vesicles (EVs) were used as treatments. It covers musculoskeletal disorders, including osteoarthritis, tendon and ligament injuries, and bone diseases; soft-tissue and oral mucosal conditions; neurological disorders; ophthalmic diseases; and internal medicine disorders, such as i...
Equine Fungal Keratitis due to Cladorrhinum bulbillosum. To describe the case details and treatment of an equine fungal keratitis case caused by Cladorrhinum bulbillosum. Methods: A 14-year-old Bashkir Curly gelding with a complicated corneal ulcer of the left eye. Methods: Corneal cytology was performed, and intraoperative samples were collected for polymerase chain reaction and for aerobic and mycologic cultures. Under general anesthesia, an inferior eyelid subpalpebral lavage system (SPL) was placed to facilitate postoperative therapy. Anterior stromal keratectomy was performed followed by cryotherapy of the keratectomy bed. A biological scaffold...
Complications Following Nictitating Membrane Resection in Horses: 92 Eyes (2015-2024). The goal of this retrospective study is to evaluate the complications following nictitating membrane resection in horses with the aim of providing valuable information on the risks of this surgical procedure. Methods: 83 horses (92 eyes). Methods: Medical records for 83 horses that underwent nictitating membrane resection in 92 eyes between February 2015 and June 2024 were reviewed. Horses were included if they had at least 1 month of follow-up data available. Owners were contacted via telephone or email questionnaire to obtain follow-up information. Complications were recorded only when pre...
Morphological and Biomechanical Characterization of Amniotic Membranes Across Species: Equine, Canine, Porcine, Ovine, and Human Samples-A Pilot Study. The use of amniotic membrane (AM) has become well established in the treatment of ocular surface disorders in both humans and animals. However, comparative studies of AM from different species remain scarce. Objective: To compare the thickness and biomechanical properties of equine, canine, porcine, and ovine AMs with those of human AM. Methods: Placentas were collected, and AMs were manually separated from the chorion. All AM samples were cryopreserved in a 1:1 solution of Dulbecco's Modified Eagle's Medium (DMEM) and glycerin at -80°C for 60 days. After thawing, samples underwent thicknes...
Efficacy of Therapeutic UVC Irradiation in Reducing Bacterial Load in Microbial Keratitis: A Retrospective Clinical Study in Veterinary Patients. To evaluate the immediate effect of therapeutic ultraviolet-C (UVC) irradiation on corneal bacterial load in veterinary patients with microbial keratitis (MK), using a retrospective analysis of clinical data collected at a UK referral ophthalmology hospital. Methods: Client-owned dogs, horses, and cats presented to a referral ophthalmology clinic with MK in 2025. Methods: Clinical records from MK cases were reviewed. For each case, paired corneal swabs were obtained immediately before and immediately after UVC irradiation with a commercially available 265 nm device (PhotonUVC). Treatment con...
Horses without ocular disease maintain similar electroretinographic responses and peripapillary retinal thicknesses across age groups. To determine the impact of age on equine electroretinography (ERG) parameters and retinal thickness in horses with healthy eyes. We hypothesized that ERG b-wave amplitudes would be significantly lower in older horses and that total retinal thickness would not vary significantly with age. Unassigned: Horses with clinically normal eyes comprising 3 age groups (≤ 10, 11 to 20, and ≥ 21 years) underwent scotopic and photopic ERGs, high-resolution fundus photography, and spectral-domain optical coherence tomography. Electroretinography results were compared between age groups using mean implici...
Antibiotics in Veterinary Ophthalmology: Resistance, Stewardship, and Emerging Antibiotic-Sparing Strategies. Antimicrobial resistance (AMR) is a growing challenge in veterinary ophthalmology, particularly in cases of bacterial keratitis, where progressive stromal infection can threaten vision and globe integrity within hours to days. This review synthesizes current evidence on pathogen distribution, antimicrobial susceptibility profiles, multidrug resistance (MDR) prevalence, and determinants of nonsusceptibility in veterinary patients, highlighting the emerging role of antibiotic-sparing alternatives. Across contemporary studies, Staphylococcus pseudintermedius, β-hemolytic streptococci, and Pseud...
The Early Ophthalmic Effects of Vatinoxan in Healthy Detomidine-Sedated Horses. To evaluate the short-term ophthalmic effects of vatinoxan, a peripherally selective alpha2-adrenoceptor antagonist, in detomidine-sedated horses. Methods: Seven healthy horses without ophthalmic disease in a randomized, masked, two-period crossover study design, with a ≥ 7-day rest period. Methods: After a bilateral palpebral block (lidocaine 40 mg) and baseline data collection, horses received intravenous detomidine (20 μg/kg [DET]) or DET with vatinoxan (200 μg/kg [DET-VAT]). Intraocular pressure (IOP) was measured from the left eye while tear production (Schirmer tear test -1; ...
A Surgical Technique for Removal of Setaria digitata From the Anterior Chamber Under Standing Sedation: Outcomes in 12 Horses. To describe a rapid surgical technique for removal of the intraocular nematode Setaria digitata from the anterior chamber of horses under standing sedation and to report clinical outcomes. Methods: Twelve client-owned horses (2021-2026) presented with a motile intracameral worm. Methods: All surgeries were performed under field conditions using standing sedation (xylazine 1.1 mg kg and butorphanol 0.1 mg kg IV), regional nerve blocks (lidocaine 2%), and topical anesthesia (proparacaine). A 2.8 mm uniplanar oblique (~45°) corneal incision was created ventrolaterally approximately 2â€...
Owner satisfaction and animal welfare after bilateral enucleation in horses. Bilateral enucleation in horses represents a challenging decision for owners, undertaken to relieve chronic, untreatable ocular pain. Emotional distress and uncertainty regarding postoperative welfare often lead to euthanasia instead of surgery. Objective: To evaluate owner perceptions of equine quality of life before and after bilateral enucleation, and to assess satisfaction with the procedure. Methods: Retrospective case series. Methods: Medical records from 21 horses that underwent bilateral enucleation between 2016 and 2024 were reviewed. Owners completed a structured survey assessing sat...
Evaluation of Circadian Variations of Central Corneal Thickness and Its Correlation With Intraocular Pressures in Healthy Horses. Circadian variations in central corneal thickness (CCT) and their correlation with intraocular pressure (IOP) have not been reported in horses. This information may be clinically relevant when interpreting IOP readings. Methods: Twenty-four eyes of 6 healthy adult gelded males and 6 healthy adult intact mares were evaluated. Rebound tonometry (TonoVet, Jorgensen Laboratories) followed by ultrasonic pachymetry (iPac Pachymeter, Reichert technologies) was performed in both eyes every 3 h over 24 h during the natural 14-h daylight summer photoperiod. Results: Central corneal thickness varied ...
Short-Term Daily Oral Administration of Cannabidiol Does Not Impact Rebound Tonometry Intraocular Pressure or Schirmer Tear Test Values in Healthy Adult Horses. To assess the effect of orally administered cannabidiol (CBD) on TonoVet measured intraocular pressure (IOP) and Schirmer tear test I (STT) in horses. Methods: Horse. Methods: This was a masked, randomized, balanced cross-over study of six healthy adult horses. Horses were randomly assigned and received 3 mg/kg CBD in sesame oil or volume matched placebo by mouth once daily for three days. Baseline and daily 4-, 12-, and 24-h post treatment IOPs were measured in triplicate without sedation or eyelid akinesia. Baseline and 24-h post final (day 3) treatment STTs were measured without sedation ...
Severe Macular Commotio Retinae Following a Fall from a Horse in a Pediatric Patient. Background and Clinical Significance: Blunt ocular trauma is a significant but often underestimated cause of visual impairment, particularly among adolescents involved in high-risk activities such as horseback riding. While most equestrian injuries affect the head and extremities, ocular trauma, especially commotio retinae, can result in severe visual complications. Case Presentation: We report the case of a 15-year-old girl who sustained blunt ocular trauma to the left eye following a fall from a horse and presented with decreased visual acuity. Multimodal imaging revealed outer retinal abnor...
Atropine induces narrowing of the superior and inferior iridocorneal angle and ciliary cleft in normal horse eyes. To investigate the effects of atropine on the iridocorneal angle (ICA) and ciliary cleft (CC) of normal equine eyes using ultrasound biomicroscopy (UBM). Unassigned: 12 normal adult horses underwent measurement of intraocular pressure (IOP), vertical and horizontal pupil diameter, and UBM of the superior, temporal, inferior, and nasal ICA/CC in both eyes. Measurements were repeated 2 hours following ophthalmic atropine 1% solution application. Measurements of the ICA and CC, including pectinate ligament distance (PLD), CC length (CCL), height of opening distance (HOD), CC area (CCA), and pecti...
Adult Equine Optic Nerve Head Measurements Using Spectral Domain Optical Coherence Tomography. To compare equine optic nerve head (ONH) measurements using spectral domain optical coherence tomography (SD-OCT) to detect clinically relevant ONH cupping. Methods: Forty-five eyes from 34 horses were categorized as CONTROL or CUPPED based on indirect ophthalmoscopy and were measured using SD-OCT: Bruch's membrane opening (BMO), optic cup width (OC), anterior laminar depth (ALD), prelaminar thickness (PLT), and cup-to-disk ratio (OC: BMO) at superior (sup.), central (ctr.), and inferior (inf.) ONH locations. Results: The OC:BMO was 0.61 ± 0.09 (sup.), 0.64 ± 0.09 (ctr.), and 0.55 ...
Evaluation of episcleral silicone matrix cyclosporine implants for presumed equine immune-mediated keratitis: a retrospective study. Immune-mediated keratitis (IMMK) is a chronic inflammatory corneal disease in horses. Long-term topical therapy with cyclosporine is often impractical, highlighting the need for sustained-release alternatives. Objective: To assess clinical response, tolerability, and duration of effect of episcleral silicone matrix cyclosporine implants (ESMC) in horses with presumed IMMK. Methods: Medical records of 12 horses (14 eyes) treated between 2019 and 2023 were retrospectively reviewed. IMMK subtypes were classified as epithelial (n = 3 eyes), anterior stromal (n = 9), or mid-stromal (n =â€...
Septic Endophthalmitis Following Suprachoroidal Cyclosporine Implant Placement in Two Horses With Equine Recurrent Uveitis. This article presents the clinical and histopathological findings from two horses that developed severe postoperative complications following suprachoroidal procedures routinely employed in the management of equine recurrent uveitis (ERU). Case 1 was a 5-year-old warmblood stallion that initially received a unilateral suprachoroidal triamcinolone injection, followed later by bilateral suprachoroidal cyclosporine implant (CSI) placement. At 9 weeks postoperatively, the right eye (which had undergone both procedures) developed secondary glaucoma necessitating enucleation. Case 2 was a 14-year-ol...
Modified Medial Canthoplasty for Correction of Euryblepharon in Two Horses. To describe a medial canthoplasty surgical procedure in two horses for correction of euryblepharon, secondary to microphthalmia, and following excision of retrobulbar fat prolapse. Methods: A 1 year old thoroughbred mare was presented for small globes and chronic ocular discharge bilaterally. Ophthalmic examination revealed microphthalmos, euryblepharon, medial canthal pocket syndrome, and dacryocystitis bilaterally with no visual impairments. A 2 year old Appaloosa gelding was presented for evaluation of a smooth, subconjunctival mass anterior to the right globe in the medial canthus. Oph...
Photodynamic therapy with infracyanine green induces keratocyte depopulation in the normal equine cornea. Use of photodynamic therapy (PDT) for the treatment of immune-mediated keratitis (IMMK) in horses is becoming common. The safety and morphologic impact on the normal equine cornea have not been investigated, and the mechanism of its efficacy is unknown. Objective: To investigate the morphologic effects and safety of in vivo PDT on healthy equine corneas. Methods: In vivo experiment. Methods: Six university-owned horses underwent unilateral corneal PDT with intrastromal infracyanine green (EmunDo®) and photoactivation with an 810 nm diode laser (500 mW for 2.5 min = 75 Joules). Compl...
Cryptophthalmia, microphthalmia, oronasal malformation, and hydrocephalus in an aborted equine fetus with umbilical torsion in the state of Mato Grosso, Brazil. Facial abnormalities and brain defects in aborted equine fetuses are rarely reported, and the causes that predispose the occurrence of this condition are difficult to identify. This work reports the morphological and tomographic findings of a case of cryptophthalmia, microphthalmia, oronasal malformation, and hydrocephalus in an aborted equine fetus with umbilical cord torsion in the state of Mato Grosso, Brazil, from a primiparous Quarter Horse female, with 7 months of gestational age. The occurrence of miscarriage was associated with compromised maternal-fetal blood flow due to umbilical cor...
Clinical Manifestations and Behaviors Associated with Equine Head and Neck Disorders. Equine head and neck disorders can present with a wide range of clinical manifestations, depending on the structures involved and disease process. Important components of the gastrointestinal, respiratory, ophthalmological, neurological, and musculoskeletal systems are contained within the head and neck, and clinical signs of disorders will result in expected clinical signs. However, clinical manifestations of disease are sometimes subtle, and when not recognized can lead to behavioral changes including undesired behaviors and poor sleep. Recognizing behavioral phenotypes of horses with proble...
Equine Corneal Stromal Invasive Squamous Cell Carcinoma: Clinical and in Vivo Confocal Microscopic Features of 7 Cases. To describe the clinical and in vivo confocal microscopy (IVCM) characteristics of horses with corneal stromal invasive squamous cell carcinoma (CSI-SCC). Methods: Retrospective study of 7 horses with histopathologically confirmed unilateral CSI-SCC. Methods: Horses with corneal CSI-SCC were examined by laser scanning IVCM. Signalment, clinical findings, and histopathology results were compared with IVCM findings. Results: Clinical ocular lesions in all horses included a heavily vascularized, opaque, gray or tan, anterior or midstromal opacity invading the cornea from the limbus. The corneal ...
Unilateral vision loss associated with corneal opacity and posterior lens luxation in the right eye of a Thoroughbred gelding: Case report. A 15-year-old Thoroughbred gelding was presented for examination due to chronic corneal opacity in the right eye, which had been noted for several years. An ophthalmic evaluation revealed dense, irregular corneal opacity; an absence of the direct pupillary light reflex; and a positive dazzle reflex. Fluorescein staining was negative and cytology of a corneal conjunctival swab identified nucleated squamous epithelial cells, but no inflammatory cells. Slit-lamp examination failed to visualize intraocular structure, and the lesion was deemed to be chronic and irreversible. An obstacle-avoidance t...
Clear cell squamous cell carcinoma in the third eyelid of a horse. Squamous cell carcinoma (SCC) is the most common ocular and periocular neoplasm of horses, typically arising from the limbus, third eyelid mucosa or mucocutaneous junctions of the upper and lower eyelids. Tumours are locally invasive, prone to recurrence and may rarely metastasize. Histological evaluation is required for definitive diagnosis and atypical SCC subtypes may be diagnostically challenging. Here we describe a clear cell SCC in the third eyelid of a 16-year-old female Quarter Horse. The red and invasive mass was surgically excised for histological evaluation. The lesion consisted of ...
Cell and Gene Therapy in Equine Ocular Disease. Equine ocular disease is common and often challenging to treat using traditional methods. This has led to the development of new therapies. Like human medicine, veterinary medicine is adopting cellular and gene therapy as innovative approaches. Equine ocular disease is a particularly promising area for these techniques. Notably, immune-mediated diseases (such as immune-mediated keratitis and equine recurrent uveitis), ulcerative keratitis, and infectious ocular diseases are of interest. Several ocular gene therapy products are approved for use in humans, and more are currently being researched...
Evaluation of corneal sensitivity in 40 Pantaneiro horses using the Cochet-Bonnet esthesiometer. Corneal sensitivity is a crucial ophthalmic parameter for the protection and maintenance of ocular health in horses. Unassigned: This study aimed to evaluate the corneal sensitivity of 40 Pantaneiro horses using the Cochet-Bonnet esthesiometer, in order to establish reference values for this population. Unassigned: The animals were considered clinically healthy after a complete ophthalmic examination. Measurements were taken in both eyes, and the data were analyzed for mean, standard deviation, and potential differences between eyes, sex, and age groups. Unassigned: The average corneal sensiti...
Repeatability and reproducibility of intraocular pressure measurements in horses using rebound and applanation tonometry. Intraocular pressure (IOP) assessment is a fundamental component of ophthalmic examinations in both veterinary and human medicine. Due to variations in IOP across species and potential differences among examiners, knowledge of normal IOP values obtained using different tonometers is essential. Unassigned: This study aimed to compare the repeatability and reproducibility of IOP values in horses obtained by three different examiners using rebound (Tonovet) and applanation (Tonopen Avia) tonometers. Unassigned: Thirty healthy criollo horses were examined. IOP was measured by three veterinarians w...
Ocular Causes for Undesired Behaviors in the Horse. Numerous ocular diseases cause visual impairment and induce ocular pain that may be associated with undesired behaviors in horses. Horses with ocular pain, indicated by the presence of blepharospasm, blepharoedema, ocular discharge or rubbing the eye, should be rested from work to avoid worsening the ocular disease and to avoid undesired behaviors associated with pain or vision impairment. Horses with ocular disease are frequently head shy. Some stoic horses may not have obvious outward clinical signs despite significant visual impairment, and as such, undesired behaviors such as spooking, bal...
Polyhexanide, Povidone-Iodine, and Hypochlorous Acid Show High In Vitro Antimicrobial Efficacy Against Pathogens Commonly Associated With Equine Infectious Keratitis. To determine the in vitro antimicrobial activity of specific antiseptics against common equine ocular surface pathogens. Methods: Staphylococcus aureus (S. aureus) (n = 12), Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) (n = 9), Enterobacter hormaechei (E. hormaechei) (n = 6), and Bacillus cereus (B. cereus) (n = 5) were collected from corneal samples of horses with ulcerative keratitis. Reference strains were included. Minimum bactericidal concentrations (MBC) of polyhexanide, povidone-iodine, and hypochlorous acid were tested using the microdilution method. ...
Detection and Longitudinal Monitoring of Cyclosporine in Horse Plasma and Urine After Ocular Implant Administration. This paper describes the detection and longitudinal monitoring of cyclosporine in plasma and urine after subconjunctival implant administration in a horse. Sensitive liquid chromatography tandem mass spectroscopy (LC-MS/MS) methods for detecting cyclosporine in horse plasma and urine have been developed and validated, with estimated limits of detection down to 1 pg/mL in both matrices. The developed methods enabled longitudinal monitoring of cyclosporine levels in blood and urine samples collected over 6 months from a horse that had received an ocular cyclosporine implant.
