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.
Saunders LZ, Bistner SI, Rubin LF.An asymptomatic, ophthalmoscopically visible proliferation affected the optic disc and nerve of two aged horses. The lesion consisted of an accumulation of foamy cells, histologically akin to fat cells, which contained an unidentified lipid-like material. The affected area and its environs were permeated by tortuous, thickened blood vessels with heavy deposits of collagen in their walls. The neuropathy is considered to be a storage disease, and although the product stored is unidentified, the lesion is similar to that of human xanthelasma. The neuropathy seems distinct from the exudative optic...
Garner A, Griffiths P.The purpose of this paper is to describe congenital defects, having no direct counterpart in
the literature, that affected both eyes of a new-born foal of pedigree racing stock, which
otherwise appeared to be entirely healthy as were both the sire and the dam.
ROBERTS SR.The research article explores the origin or causation (etiology) of an ancient horse disease known as equine periodic ophthalmia, where clinical and pathological investigations have yet to yield conclusive results. […]
Rohrbach BW, Ward DA, Hendrix DV, Cawrse-Foss M, Moyers TD.To evaluate the effect of vaccination against leptospirosis on frequency and days to recurrence of uveitis and progression of disease in horses with equine recurrent uveitis (ERU). Methods: Forty-one horses with ERU. Methods: Horses were randomly assigned to experimental (vaccinated) or control groups. Vaccine containing six serovars of Leptospira or placebo was administered, an ophthalmic examination performed and blood samples drawn on days 0, 28, 180 and 365. Antibody titers were measured against each serovar. Recurrence of uveitis was verified by ophthalmic examination. Results of the init...
Pirie CG, Pizzirani S. To describe a novel digital single lens reflex (dSLR) camera adaptor for anterior and posterior segment photography. Methods: The adaptor was used to evaluate canine, feline, and equine patients presenting to Tufts Ophthalmology service. Anterior segment imaging was conducted with the adaptor mounted between a dSLR camera body (Canon 7D) and a macro lens (Canon EF-S 60mm/f2.8). Posterior segment imaging was performed with the aid of an indirect ophthalmic lens mounted in front of the macro lens. Coaxial illumination during viewing was provided by a single white light-emitting diode (LE...
Labelle AL, Hamor RE, Townsend WM, Mitchell MA, Zarfoss MK, Breaux CB, Thomasy SM, Hall T.To determine types and frequency of ophthalmic lesions detected in neonatal foals evaluated for nonophthalmic disease at 3 veterinary referral hospitals and to investigate associations between systemic and ophthalmic diseases in these foals. Methods: Prospective cross-sectional study. Methods: 70 foals < 30 days old. Methods: Complete ophthalmic examinations were performed. Signalment, clinical signs, mentation during ophthalmic examination, results of clinicopathologic tests, and diagnosis of systemic disease were recorded. Descriptive data analysis including a χ(2) test for associations was...
Cavens VJ, Gemensky-Metzler AJ, Wilkie DA, Weisbrode SE, Lehman AM.To describe the long-term histologic and intraocular pressure (IOP) lowering effects of diode laser transscleral cyclophotocoagulation (TSCP) on the normal equine eye. Methods: Eight normal adult horses. Methods: TSCP was performed in one randomly assigned eye. Sixty spots were treated at settings of 1500 ms and 1500 mW. Two horses were randomly selected for euthanasia at 2, 4, 12, or 24 weeks post-TSCP. Both eyes were enucleated and histologically evaluated. Intraocular pressure was measured by applanation tonometry prior to TSCP, immediately post-TSCP, twice daily for 7 days post-TSCP and th...
Hoerdemann M, Yarbrough T.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...
Townsend WM, Wasserman N, Jacobi S.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...
Smith P, Samuelson D, Brooks D.The anterior vasculature of the pony eye was examined by the corrosion cast method. The anterior segment of the pony eye has a vascular pattern which is similar but distinct from that of other mammalian species. Large iridal veins collateralized directly with the anterior vortex venous system. The intrascleral plexus was present but formed a fine, radially oriented, extensive network. This contrasted to the circumferential larger-diameter intrascleral plexus noted in dogs and the canal of Schlemm present in primates. The intrascleral plexus only drained posteriorly in the pony as compared to t...
Brem S, Gerhards H, Wollanke B, Meyer P, Kopp H.Vitreous samples from 43 horses which underwent vitrectomy because of equine recurrent uveitis (ERU) were cultured for leptospires. Out of 4 vitreous samples (4/43 = 9%), leptospires could be isolated. In 3 cases, serovar grippotyphosa, and in one case, a serovar out of the serogroup Australis were identified. So for the first time, in several horses with ERU in vivo cultures of vitreous material were positive for leptospires. A strong evidence of association between leptospiral infection and uveitis is discussed for many years. In this investigation the leptospiral etiology is confirmed. Vitr...
Wada S, Yoshinari M, Katayama Y, Anzai T, Wada R, Akuzawa M.A 2-year-old Thoroughbred filly presented with ocular pain and epiphora of the left eye. The pupil was miotic and the cornea edematous near the ventro-temporal limbus, but did not retain any fluorescein. The topical antibiotics and atropine and diclofenac, and systemic flunixin meglumine and antibiotic therapy did not resolve the condition. A pink and fleshy infiltrate developed near the limbus indicating nonulcerative keratouveitis. The anterior uveitis deteriorated as manifested by the presence of dyscoria, hypopyon, and organized fibrin in the anterior chamber. Ocular signs were improved by...
Brooks DE, Clark CK, Lester GD.Corneal touch threshold (CTT) was measured in sick neonatal foals, healthy foals, and healthy adult horses with a Cochet-Bonnet aesthesiometer. The mean overall CTT for the adult horses, sick foals, and healthy foals was 4.82 +/- 0.87 cm, 3.21 +/- 0.24 cm, and 5.01 +/- 0.61 cm, respectively. The central cornea of adult horses was more sensitive than the limbal cornea. Corneal sensitivity was significantly reduced in sick neonatal foals compared to adults. The mean Schirmer I tear test values were significantly lower in foals than adults, and were 14.2 +/- 1.0 mm, 12.8 +/- 2.4 mm, and 18.3 +/- ...
Knickelbein KE, Lassaline ME, Kim S, Scharbrough MS, Thomasy SM.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...
Peyrecave-Capo X, Saulnier N, Maddens S, Gremillet B, Desjardins I.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...
Herb VM, Zehetner V, Blohm KO.This is the first description of Multiple Congenital Ocular Anomalies (MCOA) in a silver coat Missouri Fox Trotter determined to be heterozygous for the Silver PMEL17 missense mutation associated with MCOA and a silver coat in other breeds. The stallion was treated for meningoencephalitis and bilateral uveitis of unknown origin. A complete ophthalmic examination and ocular ultrasonography were performed. As an incidental finding, the patient exhibited bilateral cystic lesions restricted to the temporal anterior uvea consistent with the Cyst phenotype and was genotyped heterozygous for the Silv...
Monk CS, Brooks DE, Granone T, Garcia-Pereira FL, Melesko A, Plummer CE.To measure intraocular pressure (IOP) in horses during hoisting after induction of anesthesia. Methods: Prospective nonrandomized clinical study. Methods: Eighteen healthy adult horses aged [mean±standard deviation (SD)] 10±4.2 years and weighing 491±110 kg anesthetized for elective procedures. Methods: IOP was measured in the superior eye of each horse based on planned recumbency after induction of anesthesia. Measurements were taken directly after premedication with xylazine or detomidine with butorphanol, after induction with diazepam-ketamine, after intubation, when suspended by the ho...
Margalit E, Sadda SR.A variety of disease processes can affect the retina and/or the optic nerve, including vascular or ischemic disease, inflammatory or infectious disease, and degenerative disease. These disease processes may selectively damage certain parts of the retina or optic nerve, and the specific areas that are damaged may have implications for the design of potential therapeutic visual prosthetic devices. Outer retinal diseases include age-related macular degeneration, pathologic myopia, and retinitis pigmentosa. Although the retinal photoreceptors may be lost, the inner retina is relatively well-preser...
Badial PR, Cisneros-Àlvarez LE, Brandão CV, Ranzani JJ, Tomaz MA, Machado VM, Borges AS.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...
Blair MJ, Gionfriddo JR, Polazzi LM, Sojka JE, Pfaff AM, Bingaman DP.To evaluate the feasibility of using a subconjunctivally implanted micro-osmotic pump for continuous delivery of medication to the eyes of horses- during a 7-day period. Methods: 4 healthy adult horses. Methods: With horses restrained in a standing position, micro-osmotic pumps were implanted subconjunctivally in each eye for 7 days. The treatment eye received an atropine-loaded micro-osmotic pump (100 microl of 1.5% atropine), and the contralateral eye received a sterile saline-loaded pump (100 microl of 0.9% NaCl) as a control treatment. Pupil size was measured at 12-hour intervals until val...
Zeiss C, Neaderland M, Yang FC, Terwilliger G, Compton S.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...
Tahoun A, Elnafarawy HK, El-Sharkawy H, Rizk AM, Alorabi M, El-Shehawi AM, Youssef MA, Ibrahim HMM, El-Khodery S.This work aimed to characterize S. aureus isolates from the eyes of healthy and clinically affected equines in the Kafrelsheikh Governorate, Egypt. A total of 110 animals were examined for the presence of S. aureus, which was isolated from 33 animals with ophthalmic lesions and 77 healthy animals. We also investigated the antimicrobial resistance profile, oxacillin resistance mechanism, and the major virulence factors implicated in many studies of the ocular pathology of pathogenic S. aureus. The association between S. aureus eye infections and potential risk factors was also investigated. The...
Bentley E, Murphy CJ.A thermal cautery technique was used to treat spontaneous chronic corneal epithelial defects (SCCEDs) in 9 eyes of 8 dogs and 2 eyes of 2 horses. Animals were sedated, and a topical anesthetic was applied. A handheld thermal cautery unit was then used to make multiple, small (< or = 1 mm in diameter), superficial burns throughout the affected area. The cautery unit was applied just until the slightest degree of contraction of the collagen fibrils was observed. After the stromal bed of the defect was treated, a rim of epithelium that extended approximately 1 mm around the denuded stroma was ...
de Linde Henriksen M, Brooks DE.Standing ophthalmic surgery without general anesthesia allows for several routine ophthalmic procedures including eyelid lacerations and enucleations to be performed in the horse, but does contain increased risk of causing tissue damage arising from the inability to eliminate eye and head movements. Heavy sedation and local nerve blocks of the involved motor and sensory nerves are essential in achieving a good outcome from ophthalmic surgery in the nonanesthetized horse. The inability to use an operating microscope in standing surgery in horses prevents performing precise corneal and intraocul...
Millichamp NJ, Dziezyc J.Cataract surgeries were carried out in fifty-one eyes of 36 horses over a 15-year period. Cataracts were removed using phacofragmentation and aspiration. Useful vision was restored after surgery in 30 horses. One year after surgery 16 of the 19 horses for which follow up information was available were still visual with several still being used as working horses. At 5-6 years after surgery three horses were still visual. The most frequent intraoperative complication was tearing of the posterior lens capsule. The most frequent postoperative problem was superficial corneal ulceration. Four eyes i...
Ball MA, Rebhun WC, Trepanier L, Gaarder J, Schwark WS.The objectives of this study were to determine the concentration of itraconazole achieved in corneal tissue and aqueous humour after topical application of a 1% itraconazole ointment: to determine the effect of including dimethyl sulphoxide (DMSO) in the ointment on achievable ocular tissue itraconazole concentrations; and to assess if any gross or histopathologic ocular toxicity results from the topical application of 1% itraconazole with or without the addition of DMSO. The experimental trial consisted of 6 horses considered to have normal eyes. Each horse had one eye treated with 0.3 mL of ...
Robertson SA.Several ocular procedures, including examination, removal of corneal foreign bodies, nictitans surgery, eyelid repair, and tumor excision,can be successfully performed in the appropriately restrained and sedated standing horse. Sedation is best achieved with xylazine,with or without the addition of acepromazine. Additional analgesia can be provided with appropriate local anesthetic blocks. Surgical conditions are greatly improved by using an auriculopalpebral and supraorbital block and topical anesthetics. More elaborate standing sedation involving continuous rate infusions of lidocaine or det...
Williams LB, Pinard CL.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...
Gunsalus K, Taylor R, Croix N.To report the clinical history, surgical management, and histologic findings of meibomian gland calcification and osseous metaplasia in a horse. Methods: A 21-year-old Selle Français gelding presented with a 9 months history of blepharitis, blepharospasm, and epiphora affecting the right eye. The horse was diagnosed with meibomianitis and impaction with associated granulomas, but not treated surgically for 6 years. Methods: Physical and ophthalmic examinations, and systemic bloodwork were performed. A diamond burr debridement was performed on a corneal ulceration, and meibomian gland nodul...
Tofflemire K, Whitley EM, Allbaugh R, Ben-Shlomo G, Griggs A, Strong T, Whitley RD.To evaluate the effect of topical ophthalmic 0.005% latanoprost alone and in combination with 0.1% diclofenac on healthy horses. Methods: Twelve healthy adult horses. Methods: A randomized, masked crossover design was used with horses divided into three groups for once daily treatment in one randomly selected eye. For arm 1 of the study, Group D (n = 3) received 0.1% diclofenac, Group L (n = 3) received 0.005% latanoprost, and Group DL (n = 6) received 0.005% latanoprost and 0.2 ml of 0.1% diclofenac. For arm 2 of the study, horses from Group D and L were placed into Group DL and horses from G...
Hamor RE, Whelan NC.Corneal ulcers are one of the most common ocular disease presentations in the horse. With the use of correct diagnostic techniques and selection of an appropriate treatment regimen, most cases result in a satisfactory outcome. The eye does not respond well to inflammation, and in complicated ulcers, this should be managed aggressively using systemic NSAIDs with a high priority assigned to removing the infectious agent. Care needs to be taken to avoid topical or systemic corticosteroid use for the treatment of equine ocular disease, however, unless the clinician is completely sure that the corn...
Monclin SJ, Farnir F, Grauwels M.Tetracaine hydrochloride (THCl) has been reported to cause irritation in dogs. In man, some topical anaesthetics have been shown to disrupt the tear film. Tear break-up time (TBUT) is a useful test allowing an assessment of the quality of the precorneal tear film. Only one TBUT value has been reported in horses with no information on the technique used. Objective: To provide a method for performing the TBUT in horses and to report any side effects of a single application of THCl in clinically normal horses, particularly on the stability of the tear film. Methods: In Study 1, one drop of 0.5 or...
