The study of equine eyes encompasses various anatomical, physiological, and pathological aspects of the horse's visual system. The equine eye is a complex organ adapted for a wide field of vision and low-light conditions, which is essential for the survival of prey animals. Key components include the cornea, lens, retina, and optic nerve, each playing a role in capturing and processing visual information. Common ocular conditions in horses include uveitis, cataracts, and corneal ulcers, which can affect vision and overall health. Diagnostic techniques such as ophthalmoscopy and ultrasonography are employed to assess eye health and detect abnormalities. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, function, and diseases of the equine eye, as well as advancements in diagnostic and therapeutic approaches.
Smith LH, Adams L, Derré M, Townsend WM.To describe the successful use of endoscopy to visualize and place a soft canine ureteral stent to relieve a chronic nasolacrimal duct (NLD) obstruction in a horse. Methods: A 7-year-old, Quarter horse gelding. Methods: Under general anesthesia, retrograde nasolacrimal endoscopy was performed using an 8.5 Fr Storz Flex XC ureteroscope through the nasal punctum (NP). An obstructive web of fibrous tissue was visualized approximately 20 cm proximal to the NP. A 0.035″/150 cm hydrophilic guidewire was passed normograde from the ventral lacrimal punctum and used to puncture the stenotic tissu...
Mo PM, Picard J, Gummow B.Fungi are ubiquitous in the environment and part of the commensal microflora on the conjunctiva of equine eyes. North Queensland, being tropical, presents an ideal environment for fungi growth. When the cornea is injured, fungi can invade the corneal stroma, resulting in keratomycosis. The objectives of this study were to determine the fungal species specific to the eyes of horses in the Townsville region; to investigate the potential risk factors associated with the presence of fungi; and to test their susceptibility to antifungals to create an empirical guide for treatment. The eyes of forty...
Charnock LN, Davidson MG, Keys DA, Gilger BC, McMullen RJ.To evaluate the normal refractive state in horses in NCSU and ECMR and determine the prevalence of naturally occurring refractive errors and their association with breed, age, coat color, iris color, sex, and geographic location. Methods: Horses from NCSU (January 2009-November 2012) and ECMR (January 2013-September 2016) underwent ophthalmic examination and streak retinoscopy. Location, color, breed, sex, and iris color were recorded. Gross and net refractive values for each meridian (horizontal and vertical), spherical refraction, astigmatism for both eyes, and anisometry were recorded, and ...
Launois T, Hontoir F, Dugdale A, Dedieu M, Vandeweerd JM.Horses with recurrent uveitis can be treated by intravitreal injection of low dose gentamicin under sedation and after local anesthetic techniques including the retrobulbar nerve block. Since it is reported that retinal degeneration can be secondary to an acute increase of intraocular pressure (IOP), the current randomized controlled study was carried out in order to investigate the changes in IOP following retrobulbar anesthesia, with two different volumes of local anesthetic (lidocaine) solution (10 and 5 mL), and intravitreal injection of 6 mg gentamicin in two different volumes of solution...
Angeluci GC, Ricci CL, Passareli JVGC, Estanho GJG, Oliveira AS, Santos SGA, Giuffrida R, Rodrigues M, Andrade SF.Measurement of the intraocular pressure (IOP) is a useful diagnostic tool in equine ophthalmology. Handheld tonometers, such as Tonovet and Tonovet Plus (rebound), Tono-Pen AVIA Vet (applanation), and Kowa HA-2 (applanation using the Goldmann methodology) are used to obtain IOP measurements in veterinary medicine. Objective: To compare and evaluate the accuracy of four handheld tonometers in measuring IOP using different methodologies in healthy horses. Methods: In vivo experiment and cross-sectional survey of healthy horses. Methods: Intraocular pressure was measured in 72 eyes of 36 horses. ...
Peraza J, Hector RC, Lee S, Terhaar HM, Knych HK, Wotman KL.Acetaminophen (paracetamol) is increasingly used to treat painful conditions in horses but its ocular penetration has not been studied. Objective: To determine whether orally administered acetaminophen penetrates the aqueous humour of the normal equine eye and report an aqueous humour:serum acetaminophen concentration ratio in horses. Methods: In vivo experiment. Methods: Six privately owned horses with normal ophthalmic examinations weighing 568 ± 65 kg (mean ± standard deviation) and aged 11 ± 4 years were given 20 mg/kg acetaminophen orally every 12 h for a total of s...
Lazareva Y, Rayisyan M, Mironova E.Keratitis is a common cause of eye diseases in horses, often resulting in complete loss of vision. The purpose of this article is to study the features of the clinical picture of primary and secondary keratitis in horses, depending on the form of the course of the disease. The study was conducted in 2019 at 22 private horse breeding farms. The study involved 80 horses with keratitis, which were divided into two equal groups depending on the diagnosis of primary or secondary keratitis. The effectiveness of the therapies was compared 1, 3, and 6 months after the start of treatment. Following a 1...
Martín-Suárez EM, Mesa P, Portillo M, Morgaz J, Moreno O, Guisado A, Galán-Rodríguez A.This study sought to compare the Schirmer Tear Test (STT)-1 results at 30 (STT30) versus 60 (STT60) seconds in healthy horses. This study included a total of 56 healthy horses. STT-1 was performed in both eyes, right eye first, and the wetting lengths were measured in STT30 and STT60. To evaluate the reduction of the initial reflex phase, the wetting length velocity was measured during the first 30 seconds. The effects of eye, age, weight, sex, and ambient temperature and humidity on STT values were evaluated. Mean (standard deviation) STT30 and STT60 were 19.06 (3.88) and 24.26 (4.50) mm. The...
Bartolomé E, Perdomo-González DI, Ripollés-Lobo M, Valera M.Horses have been valued for their diversity of coat color since prehistoric times. In particular, the pleiotropic effect that coat color genes have on behavior determines the way the horse perceives and reacts to its environment. The primary aim of this study was to evaluate the influence of coat color on basal reactivity assessed with infrared thermography as eye temperature at rest (ETR), determine their relation with the results obtained by these horses in Show Jumping competitions and to estimate the genetic parameters for this variable to test its suitability for genetic selection. A Gene...
Charnock LN, Boveland SD, Groover ES, Moore PA, McMullen RJ.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...
Mirzaeei S, Faryadras FB, Mehrandish S, Rezaei L, Daneshgar F, Karami A.Prolonging the drug release can be a suitable approach to overcome the challenges related to topical ophthalmic administration of drugs especially the ones prescribed for chronic ailments. The sustained delivery of the drug would reduce the required frequency of administration which could extremely improve patient compliance and feeling of well-being. This study aimed to develop nanofibrous inserts for sustained ophthalmic delivery of timolol maleate (TIM) for the treatment of glaucoma. Unassigned: Polycaprolactone-based nanofibers containing TIM were prepared using pure polycaprolactone or a ...
Romero BF, Iglesis García M, Gil Molino M, Gómez L, Galapero J, Parejo C, Martín Cuervo M.Equine uveitis is a common eye disease that affect horses from different breeds, ages, and genders. Uveitis has been described as inflammation of the uvea secondary immunomediated processes or eye trauma. Renal cell carcinoma (RCC) is the most common tumor that can affect the equine kidneys. The present case describe a horse that was referred to the Veterinary Teaching Hospital of the University of Extremadura with bilateral uveitis. The horse was treated for the primary complain but the horse collapse and die during hospitalization. At necropsy, a tumoral mass in kidney with extensive in othe...
Crabtree E, Uribe K, Smith SM, Roberts D, Salmon JH, Bower JJ, Song L, Bastola P, Hirsch ML, Gilger BC.Equine recurrent uveitis (ERU) is a spontaneous, painful, and vision threatening disease affecting up to 25% of equine populations worldwide. Current treatments of ERU are non-specific and have many side effects which limits them to short-term use. In order to develop an effective therapy for ERU, we investigated the use of adeno-associated virus (AAV) gene therapy, exploiting a natural immune tolerance mechanism induced by equine interleukin-10 (Equine-IL10). The purpose of this study was to evaluate the therapeutic efficacy of a single intravitreal (IVT) dose of AAV8-Equine-IL10 gene therapy...
Aragona F, Di Pietro S, Arfuso F, Fazio F, Piccione G, Giudice E, Giannetto C.The aim of the present study was to investigate the response to physical exercise of some ocular physiological variables (ocular temperature and intraocular pressure) in horses performing a jumping course in the morning (a.m.) or in the afternoon hours (p.m.), before and after the exercise, in correlation with the rectal temperature. Data collection was carried out on 14 clinical healthy Italian saddle horses. All horses were trained from 9:00 to 10:00 a.m. and from 19:00 to 20:00 p.m. according to a specific training program. Ocular temperature (OT), rectal temperature (RT) and intraocular pr...
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...
Quéré E, Chahory S.Painful eye conditions are a therapeutic challenge in horses. Subpalpebral lavage (SPL) treatment systems allow topical aqueous medications to be conveniently, safely, and frequently administered to the ocular surface. The aim of this retrospective study was to describe the outcomes and the complications associated with the location of the SPL treatment systems, in the superior or inferior eyelid in horses in a university practice. Clinical records of all horses admitted to the National Veterinary School of Alfort between January 2004 and October 2021, in which a SPL treatment system was used ...
Sheridan CK, Myrna KE, Nunnery CM, Czerwinski SL.To determine the prevalence of ocular disease in draft horses in the United States. Methods: Draft horses of various breeds and ages. Methods: Nondilated ophthalmic examination was performed using slit lamp biomicroscopy and indirect ophthalmoscopy. Intraocular pressures were measured when possible. Results: One hundred sixty-five draft horses were examined. Age range: 10 days to 33 years (mean 10.8 years, median 10 years); 87 geldings (52.7%), 71 mares (43.0%), 7 stallions (4.2%); 64 Percherons (38.8%), 51 Belgians (30.9%), 29 Clydesdales (17.6%), 15 Shires (9%), and 6 other draft bre...
Starke SD, May SA.A large number of lameness indicators have been suggested for the visual equine lameness assessment. However, it remains unknown which of these are commonly used by experts. Twenty-four expert lameness assessors from 10 leading UK institutions viewed 28 video clips of sound and mildly lame horses (median score 2/10). Horses were shown at trot in a straight line (rear and front view) and circle (side view, left and right rein). Eye tracking data were collected at 60 Hz while participants evaluated each clip. A questionnaire captured contextual information. During assessment on the straight lin...
Knickelbein KE, Lassaline ME, Kim S, Thomasy SM.The iridocorneal angle (ICA) is the major pathway of aqueous humour outflow from the anterior chamber of the eye. Ultrasound biomicroscopy (UBM) has been utilised to characterise the morphology of this drainage pathway in numerous species. UBM may allow for early recognition of aqueous humour outflow obstructions in horses, allowing for earlier recognition of risk for glaucoma, a vision-threatening and painful disease. UBM morphology of the normal equine ICA has yet to be described. Objective: To determine the ultrasonographic morphology of the equine ICA by UBM in standing sedated horses. Met...
Stonex TM, Zibura AE, Andres M, Gilger BC, Oh A.To describe the use of 1% polidocanol as the sole treatment for a superficial orbital venous malformation in a horse. Methods: A 23-year-old Welsh Cobb cross gelding with a distensible swelling affecting the left lower eyelid, and secondary palpebral margin abnormalities and superficial keratitis. Methods: Color flow Doppler ultrasonography revealed non-pulsatile blood flow within the tortuous vascular network most consistent with a superficial orbital venous malformation appearing to involve the lateral palpebral and transverse facial veins. An intravenous catheter was placed within the later...
Attaai AH, Hussein MT, Aly KH, Abdel-Maksoud FM.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...
Santibáñez R, Lara F, Barros TM, Mardones E, Cuadra F, Thomson P.The ocular microbiome in horses is poorly described compared to other species, and most of the information available in the literature is based on traditional techniques, which has limited the depth of the knowledge on the subject. The objective of this study was to characterize and predict the metabolic pathways of the ocular microbiome of a group of healthy horses. Conjunctival swabs were obtained from both eyes of 14 horses, and DNA extraction was performed from the swabs, followed by next generation sequencing and bioinformatics analyses employing DADA2 and PICRUSt2. A total of 17 phyla we...
Vercruysse EM, Narinx FP, Rives ACM, Sauvage AC, Grauwels MF, Monclin SJ.To describe bacterial isolates and associated antibiotic resistance from horses with ulcerative keratitis in Belgium. Methods: Medical records from horses with ulcerative keratitis presented to the ophthalmology service of the Veterinary teaching hospital of Liege, Belgium, between 2014 and 2021 were evaluated. Bacterial isolates were identified and VITEK® 2 (Biomérieux) provided antimicrobial susceptibility testing and resistance detection. Results: Two hundred eyes of 196 horses were sampled. Ninety-seven eyes had a positive bacterial culture (48.5%) and 139 bacterial isolates were identif...
Fraczkowska K, Zak-Bochenek A, Siwinska N, Rypula K, Ploneczka-Janeczko K.From a clinical point of view, knowledge of the commensal microbial flora of the conjunctival sac in healthy individuals proves to be of great importance. The aim of this study was to assess the presence and the composition of normal ocular microflora of healthy donkeys. Fourteen clinically healthy donkeys () participated in the study. After prior ophthalmological examination, which showed no abnormalities, a conjunctival swab was taken from each donkey from the right and left eye. Species-specific identification was based on a morphological assessment of bacterial colonies stained with the Gr...
Winter JC, Thieme K, Eule JC, Saliu EM, Kershaw O, Gehlen H.Primary photosensitization rarely occurs in horses and can easily be misinterpreted. Descriptions of the disease in horses after ingestion of parsnip are lacking. The aim of this case series was to describe the dermatological and ocular changes due to photosensitization and to raise awareness of parsnip being a possible aetiologic agent. Methods: Nine horses from three different stables in Berlin and Brandenburg, Germany, presented variable degrees of erythema, scaling, crusting and necrosis of unpigmented skin at the head and prepuce. Horses were of different breeds with a median age of 15 ...
Fingerhut L, Yücel L, Strutzberg-Minder K, von Köckritz-Blickwede M, Ohnesorge B, de Buhr N.Equine recurrent uveitis (ERU) is a common ocular disease of horses and described as a model for human autoimmune uveitis. This immune-mediated, inflammatory condition progressively destroys the eye, ultimately leading to blindness. Genetic and autoimmune factors, next to infections with Leptospira, are discussed as key factors in the pathogenesis. Furthermore, a release of neutrophil extracellular traps (NETs) by activated neutrophils is involved. NETs are composed of decondensed chromatin and proteins that can immobilize invading pathogens. However, if NETs accumulate, they can contribute to...
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...
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...
Ollivier FJ, Brooks DE, Kallberg ME, Komaromy AM, Lassaline ME, Andrew SE, Gelatt KN, Stevens GR, Blalock TD, van Setten GB, Schultz GS.To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers. Methods: Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis. Methods: Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% alpha1-proteinase inhi...
Roberts K, Hemmings AJ, Moore-Colyer M, Parker MO, McBride SD.A relationship between dopamine and temperament has previously been described in human cases of dopaminergic dysfunction. Adjustment in temperament prior to disease manifestation can enable the early identification of individuals at risk of such conditions, and scope exists to extend this application of temperament alterations to cases of dopaminergic dysfunction in horses. A multivariate and mixed-methods approach utilising a questionnaire along with two inferred measurements of dopamine activity (Spontaneous Blink Rate [SBR] and behavioral initiation rate [BIR]) were recorded from direct obs...
Evans K, Smith M, McDonough P, Wiedmann M.A retrospective study was conducted to determine case histories, microbiological characteristics, and molecular subtypes associated with Listeria monocytogenes infections of the eye in large animals. For selected cases, environmental L. monocytogenes contamination patterns on case farms were also evaluated to probe for potential sources and spread of listerial eye infections. Records of 170 L. monocytogenes isolates from animal infections were reviewed to determine the fraction of isolates associated with eye infections (conjunctivitis, keratitis, and uveitis) of animals and to gather informat...
Gaarder JE, Rebhun WC, Ball MA, Patten V, Shin S, Erb H.To compare initial clinical appearances, healing mechanisms, risk factors, and outcomes of horses with fungal keratitis. Methods: Retrospective analysis. Methods: 52 horses (53 eyes) with fungal keratitis. Methods: Medical records and clinical photographs of eyes were reviewed. Keratomycoses were categorized on the basis of clinical appearance at initial examination and pattern of healing. Results: Five distinct forms of mycotic keratitis were recognized. Of 53 affected eyes, 34 (64%) retained sight and had varying degrees of corneal scarring after treatment, 6 (11%) had a cosmetic appearance ...
Andersson LS, Juras R, Ramsey DT, Eason-Butler J, Ewart S, Cothran G, Lindgren G.Equine Multiple Congenital Ocular Anomalies (MCOA) syndrome consists of a diverse set of abnormalities predominantly localized to the frontal part of the eye. The disease is in agreement with a codominant mode of inheritance in our horse material. Animals presumed to be heterozygous for the mutant allele have cysts originating from the temporal ciliary body, peripheral retina and/or iris. In contrast, animals predicted to be homozygous for the disease-causing allele possess a wide range of multiple abnormalities, including iridociliary and/or peripheral retinal cysts, iridocorneal angle abnorm...
Evans KE, McGreevy PD.It has recently been reported that a strong correlation exists between the distribution of retinal ganglion cells and nose length in the domestic dog. To determine if this phenomenon occurs in another domestic species with diverse skull morphology, the current study examined the distribution of retinal ganglion cells in 30 horses from a variety of breeds. There was a significant variation in the density of ganglion cells found across the retinae. Breed was a significant predictor for ganglion cell density within the visual streak. A strong positive correlation exists between the density of gan...
Chagnaud BP, Simmers J, Straka H.In guiding adaptive behavior, efference copy signals or corollary discharge are traditionally considered to serve as predictors of self-generated sensory inputs and by interfering with their central processing are able to counter unwanted consequences of an animal's own actions. Here, in a speculative reflection on this issue, we consider a different functional role for such intrinsic predictive signaling, namely in stabilizing gaze during locomotion where resultant changes in head orientation in space require online compensatory eye movements in order to prevent retinal image slip. The direct...
Schwink KL.Uveitis (inflammation of the iris, ciliary body, or choroid) is a potentially blinding condition with a significant economic impact on the horse industry. Variable symptoms are described, as well as a considerable range of structural and functional sequelae. Known causes of initial episodes include bacterial, viral, traumatic, and parasitic insults, with recurrence by immunologic mechanisms. Treatment strategies and management recommendations that may reduce the incidence or severity of episodes are discussed.
Curto E, Messenger KM, Salmon JH, Gilger BC.To determine whether horses with clinically diagnosed Equine Recurrent Uveitis (ERU) and those with Leptospirosis infection have a specific cytokine profile in their aqueous humor (AH) and serum that differs from horses with uveitis secondary to other ocular inflammatory processes and from horses with normal eyes. Methods: Twenty-five client-owned horses with uveitis that were presented to the North Carolina State University Ophthalmology Service, and four University-owned horses without history or clinical signs of ocular disease. Methods: Samples of AH and serum were obtained from horses wit...
Hampson ECGM, Gibson JS, Barot M, Shapter FM, Greer RM.To identify bacteria and fungi found on the conjunctival surface of normal horse eyes; to investigate potential risk factors for these microflora; and to determine their susceptibility to common topical ophthalmic antimicrobials. Methods: A total of 95 client-owned horses were studied. Methods: Horses within sub-tropical Australia (South-East Queensland) were sampled once between April 2012 and March 2013. A conjunctival swab was taken from each eye and cultured for aerobic bacteria and fungi. Organisms were identified by colony morphology and phenotype. Antimicrobial disk diffusion susceptibi...
Grahn BH, Pinard C, Archer S, Bellone R, Forsyth G, Sandmeyer LS.Multiple congenital ocular anomalies in purebred and crossbred Rocky and Kentucky Mountain horses in Canada are frequently diagnosed with biomicroscopic and indirect ophthalmoscopic examination. In order of frequency detected, these include temporal ciliary epithelial cysts; iridal hypoplasia; prominent corneas; focal temporal retinal degeneration related to ciliary cysts; and, rarely, retinal detachment. A pedigree analysis confirms a dominant mode of inheritance with incomplete penetrance and with a linkage to coat color. Des anomalies oculaires congénitales multiples chez des chevaux Rock...
Teifke JP, Löhr CV.One hundred and six squamous cell carcinomas (SCCs) of cattle, horses, cats and dogs were analysed immunohistochemically for overexpression of p53 protein. The monoclonal antibody pAb 240, which recognizes only mutant p53, was used. Of 41 bovine ocular SCCs, 26 (63.4%) showed p53 nuclear reactivity. All of six (100%) equine ocular SCCs and seven of nine (77.7%) SCCs of the equine penis or vulva gave positive reactions. In nine of 11 (81.8%) feline SCCs of the ear and in seven of 14 (50%) feline SCCs of other locations, p53 immunoreactivity was detected. Only seven of 25 (29.5%) canine cutaneou...
Miller PE, Pickett JP, Majors LJ.Comparisons were made of measurements obtained in horses, using 2 applanation tonometers in vivo and in vitro. In vitro comparisons indicated that although neither instrument accurately recorded intraocular pressure (IOP), compared with manometric measurements, results of both instruments indicated linear digression from manometric IOP values that could readily be corrected, thereby accurately estimating IOP in horses. For tonometer 1 (MacKay-Marg), calculated actual IOP = 1.48 - 0.9 mm of Hg; and for tonometer 2 (Tono-Pen), calculated actual IOP = 1.38 + 2.3 mm of Hg. The coefficients of dete...
Schanz L, Krueger K, Hintze S.Identifying valid indicators to assess animals' emotional states is a critical objective of animal welfare science. In horses, eye wrinkles above the eyeball have been shown to be affected by pain and other emotional states. From other species we know that individual characteristics, e.g., age in humans, affect facial wrinkles, but it has not yet been investigated whether eye wrinkle expression in horses is systematically affected by such characteristics. Therefore, the aim of this study was to assess how age, sex, breed type, body condition, and coat colour affect the expression and/or the as...
Timney B, Keil K.Although horses have laterally-placed eyes, there is substantial binocular overlap, allowing for the possibility that these animals have stereopsis. In the first experiment of the present study we measured local stereopsis by obtaining monocular and binocular depth thresholds for renal depth stimuli. On all measures, the horses' binocular performance was superior to their monocular. When depth thresholds were obtained, binocular thresholds were several times superior to those obtained monocularly, suggesting that the animals could use stereoscopic information when it was available. The binocul...
Mack M, Kowalski E, Grahn R, Bras D, Penedo MCT, Bellone R.A unique eye color, called tiger-eye, segregates in the Puerto Rican Paso Fino (PRPF) horse breed and is characterized by a bright yellow, amber, or orange iris. Pedigree analysis identified a simple autosomal recessive mode of inheritance for this trait. A genome-wide association study (GWAS) with 24 individuals identified a locus on ECA 1 reaching genome-wide significance ( = 1.32 × 10). This ECA1 locus harbors the candidate gene, (), (), with known roles in pigmentation in humans, mice, and zebrafish. Humans with compound heterozygous mutations in have oculocutaneous albinism (OCA) type...
Ehrenhofer MC, Deeg CA, Reese S, Liebich HG, Stangassinger M, Kaspers B.Investigations of the pathophysiology of ocular diseases require a detailed knowledge of the microanatomy of the eye. The available information is still inadequate for the equine retina despite the importance of eye diseases in equine medicine. Here we provide a comprehensive analysis of the histologic features of the horse eye as a reference for future studies. Thirty normal eyes of 15 healthy horses were examined immediately after slaughter. The retina of the horse differs considerably in the degree and quantity of neurons and glial elements as well as in vascular patterns compared to the re...
Rosa M, Cardozo LM, da Silva Pereira J, Brooks DE, Martins AL, Florido PS, Stussi JS.The conjunctival fungal flora of 32 adult horses with normal eyes (n = 64) from the State of Rio de Janeiro in Brazil was identified in the fall of 2000 using horses of different breeds, both genders and aged 5-19 years old. The culture samples were taken from the conjunctival sac of both eyes with a sterile cotton swab wetted with saline solution, seeded in Sabouraud's dextrose agar with chloramphenicol, and incubated for 5 days at an average temperature of 25 degrees C. The number of fungal colonies per eye varied between 0 and 250 colony forming units (CFUs). There were often differences in...
Borchers K, Ebert M, Fetsch A, Hammond T, Sterner-Kock A.Equine herpes virus 2 (EHV-2), a gamma(2)-herpesvirus, is common in horses of all ages. Its role as a primary pathogen is unclear but there is an association between EHV-2, respiratory disease and keratoconjunctivitis. The purpose of this study was to gain more information on the prevalence of EHV-2 DNA in conjunctival swabs from horses with and without ocular disease and to define the anatomical site and cell type harbouring viral genome or antigen. By polymerase chain reaction (PCR) 22 out of 77 (28.6%) ocular swabs of clinically healthy and only 4 out of 48 (8.3%) samples from diseased hors...
Douglas LC, Yi NY, Davis JL, Salmon JH, Gilger BC.In vitro photosensitivity of rapamycin (RAPA) and ocular toxicity and distribution of intravitreal and subconjunctival RAPA was evaluated in normal horses. RAPA (2.5 mg, 5 mg, and 10 mg) was placed in 10 mL of PBS and maintained in a water bath at 37 degrees C, kept in the dark or subjected to room light, and sampled for up to 3 months for RAPA levels. Six normal adult horses received either 5 mg (n = 2) or 10 mg (n = 2) of RAPA intravitreally or 10 mg (n = 2) subconjunctivally. Ophthalmic exams and electroretinography (ERG) were performed prior to injection and on days 1, 7, 14, and 21 post-i...
Bertolucci C, Giudice E, Fazio F, Piccione G.The present study was undertaken to investigate the existence of intraocular pressure (IOP) rhythms in athletic thoroughbred horses maintained under a 24 h cycle of light and darkness (LD) or under constant light (LL) or constant dark (DD) conditions. We identified an IOP circadian rhythm that is entrained to the 24 h LD cycle. IOP was low during the dark phase and high during the light phase, with a peak at the end of the light phase (ZT10). The circadian rhythm of IOP persisted in DD (with a peak at CT9.5), demonstrating an endogenous component in IOP rhythm. As previously shown in other mam...
Malalana F, Blundell RJ, Pinchbeck GL, Mcgowan CM.Equine recurrent uveitis (ERU) is a common cause of ocular pain and blindness in horses. Leptospira spp. have been commonly implicated in the pathophysiology of ERU in mainland Europe and the USA. No recent studies have been carried out in the UK, but Leptospira is reported not to be a major factor in the aetiology of ERU in the UK. Objective: To establish the prevalence of Leptospira-associated ERU in the UK and to identify the serovars involved in these cases; to compare serum vs. aqueous humour antibody levels in cases and controls in order to confirm the diagnosis of Leptospira-associated ...
Aragona F, Di Pietro S, Arfuso F, Fazio F, Piccione G, Giudice E, Giannetto C.The aim of the present study was to investigate the response to physical exercise of some ocular physiological variables (ocular temperature and intraocular pressure) in horses performing a jumping course in the morning (a.m.) or in the afternoon hours (p.m.), before and after the exercise, in correlation with the rectal temperature. Data collection was carried out on 14 clinical healthy Italian saddle horses. All horses were trained from 9:00 to 10:00 a.m. and from 19:00 to 20:00 p.m. according to a specific training program. Ocular temperature (OT), rectal temperature (RT) and intraocular pr...
Pollock PJ, Russell T, Hughes TK, Archer MR, Perkins JD.To report a technique for eye enucleation in standing sedated horses and to report outcome in 40 horses. Methods: Retrospective study. Methods: Horses (n=40) requiring eye enucleation. Methods: The eye was enucleated using a transpalpebral technique in 40 horses restrained in stocks and sedated. Anesthesia of orbital structures was provided by local nerve blocks and infiltration of the surgical site with local anesthetic solution. Results: Affected eyes were successfully enucleated with the horse standing. Short-term complications included moderate swelling (5 horses) and wound discharge (1). ...
Linardi RL, Megee SO, Mainardi SR, Senoo M, Galantino-Homer HL.The limited characterization of equine skin, eye and hoof epithelial stem cell (ESC) and differentiation markers impedes the investigation of the physiology and pathophysiology of these tissues. Objective: To characterize ESC and differentiation marker expression in epithelial tissues of the equine eye, haired skin and hoof capsule. Methods: Indirect immunofluorescence microscopy and immunoblotting were used to detect expression and tissue localization of keratin (K) isoforms K3, K10, K14 and K124, the transcription factor p63 (a marker of ESCs) and phosphorylated p63 [pp63; a marker of ESC tr...
Voelter K, Vial Z, Pot SA, Spiess BM.To evaluate leptospiral antibody prevalence in 65 horses with ERU and compare outcome in 36 surgically treated eyes (2010-2015). Methods: Retrospective data analysis of horses with ERU (n = 65). C-value calculation with microagglutination assay titer (MAT) results for Leptospira spp. Evaluation of follow-up data after pars plana vitrectomy (PPV, n = 21 eyes) and suprachoroidal cyclosporine device implantation (SCDI, n = 15 eyes). Differences between groups were statistically analyzed using Fishers exact test, significance set at P < .05. Results: Positive leptospiral titers were found ...
Hisey EA, Hermans H, Lounsberry ZT, Avila F, Grahn RA, Knickelbein KE, Duward-Akhurst SA, McCue ME, Kalbfleisch TS, Lassaline ME, Back W, Bellone RR.Distichiasis, an ocular disorder in which aberrant cilia (eyelashes) grow from the opening of the Meibomian glands of the eyelid, has been reported in Friesian horses. These misplaced cilia can cause discomfort, chronic keratitis, and corneal ulceration, potentially impacting vision due to corneal fibrosis, or, if secondary infection occurs, may lead to loss of the eye. Friesian horses represent the vast majority of reported cases of equine distichiasis, and as the breed is known to be affected with inherited monogenic disorders, this condition was hypothesized to be a simply inherited Mendeli...
Rames DS, Miller DK, Barthel R, Craig TM, Dziezyc J, Helman RG, Mealey R.Ocular contents from a horse with a 4-week history of severe unilateral uveitis were submitted for histopathologic examination. A severe unilateral granulomatous chorioretinitis with intralesional Halicephalobus deletrix was diagnosed. The horse developed progressive neurologic signs several days following the surgery to remove ocular contents and implant a prosthesis and was subsequently euthanatized. A severe multifocal granulomatous encephalitis with intralesional H. deletrix, localized primarily to the optic chiasm, thalamus, and brain stem, was diagnosed from tissues acquired at necropsy....
McMullen RJ, Gilger BC.To determine ocular dimensions (A- and B-scan ultrasound) and corneal curvature (radius of corneal diameter determined in B-scan ultrasound) in the equine eye and to calculate the appropriate dioptric power for a posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of horses undergoing lens extraction. Methods: Fourteen clinically normal adult horses of various breeds. Additionally, for comparison, one American Miniature colt foal, and one 2.5-year-old Shire gelding were examined. Methods: B-scan ultrasound was performed on one eye from each horse. One eye from ...
