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Topic:Eyes
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.
Inhibition of experimental autoimmune uveitis by intravitreal AAV-Equine-IL10 gene therapy. 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...
Correlation between Ocular and Rectal Temperature with Intra Ocular Pressure in Horse during Exercise. 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...
Calcification and osseous metaplasia of the meibomian glands of a horse. 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...
Outcomes and Complications Associated with Superior and Inferior Subpalpebral Lavage Treatment Systems Placed in 61 Equine Eyes (2004-2021). 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 ...
Survey of ocular abnormalities in draft horses. 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...
Expert visual assessment strategies for equine lameness examinations in a straight line and circle: A mixed methods study using eye tracking. 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...
Ultrasound biomicroscopy of the equine iridocorneal angle. 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...
Polidocanol monotherapy for a superficial orbital venous malformation in a horse. 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...
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...
Ocular Microbiome in a Group of Clinically Healthy Horses. 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...
Equine ulcerative keratitis in Belgium: Associated bacterial isolates and in vitro antimicrobial resistance in 200 eyes. 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...
Aerobic Commensal Conjunctival Microflora in Healthy Donkeys. 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...
Photodermatitis and ocular changes in nine horses after ingestion of wild parsnip (pastinaca sativa). 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 ...
Ex Vivo and In Vitro Analysis Identify a Detrimental Impact of Neutrophil Extracellular Traps on Eye Structures in Equine Recurrent Uveitis. 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...
The Prevalence and Molecular Biology of Staphylococcus aureus Isolated from Healthy and Diseased Equine Eyes in Egypt. 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...
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...
Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect. In standing ophthalmic surgery in horses, a retrobulbar nerve block (RNB) is often placed blindly for anesthesia and akinesia. The ultrasound (US)-guided RNB may have fewer complications, but the two techniques have only been compared once in equine cadavers. This study compares the techniques for success and complication rates and analyzes the effect of training on US guidance. Twenty-two equine cadavers were divided into three groups: blind RNBs were performed bilaterally in eight cadavers, US-guided RNBs were performed bilaterally in seven cadavers, and after US-guided training, blind RNBs ...
Monitoring Blinks And Eyelid Twitches In Horses To Assess Stress During The Samples Collection Process. To assess stress in horses, a method of monitoring eye blinks (full and half) and eyelid twitches while collecting saliva and blood samples before and after annual intensive police training was carried out. This noninvasive monitoring method was used to determine whether blood collection, which is considered invasive, is more stressful for horses than saliva collection. We discovered no significant difference in stress related manifestations between saliva sampling and blood collection in our study. In both cases, sampling (blood and saliva) reduced the number of full and half eye blinks. Base...
Effects of 0.0015% preservative-free tafluprost on the equine eye. The purpose of this study was to determine the effects and potential side effects of topical preservative-free (PF) tafluprost 0.0015% in ophthalmologically normal horses. Methods: Five adult grade horses. Methods: One of the eyes of each horse was randomly chosen as the "treatment" eye, and consequently, the contralateral eye served as the "control." A single dose of PF tafluprost 0.0015% (0.2 mL) was instilled in the treated eye of each horse. Intraocular pressure (IOP), Schirmer's tear test (STT) levels of each eye, and an ophthalmic examination were performed at T0 (baseline), T30, T120, ...
Artificial intelligence as a tool to aid in the differentiation of equine ophthalmic diseases with an emphasis on equine uveitis. Due to recent developments in artificial intelligence, deep learning, and smart-device-technology, diagnostic software may be developed which can be executed offline as an app on smartphones using their high-resolution cameras and increasing processing power to directly analyse photos taken on the device. Objective: A software tool was developed to aid in the diagnosis of equine ophthalmic diseases, especially uveitis. Methods: Prospective comparison of software and clinical diagnoses. Methods: A deep learning approach for image classification was used to train software by analysing photograph...
Relationship between maximum eye temperature and plasma cortisol concentration in racehorses during intensive training. The aim of the study was to determine the utility of maximum eye temperature measured by infrared thermography (IRT) as a stress indicator compared with plasma cortisol concentration in Thoroughbred and Arabian racehorses. The study included thirty racehorses undergoing standard training for racing. Measurements of maximum eye temperature and blood collection for plasma cortisol concentration were carried out before training (BT), and within 5 (5AT) and 120 minutes (120AT) after the end of the each training session in three repetitions, with a monthly interval. Both parameters were elevated at...
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...
Salivary cortisol and eye temperature changes during endurance competitions. The purpose of this study was to investigate the usefulness of salivary cortisol (SC) and eye temperature measured by infrared thermography (IRTET) as biomarkers to manage competitions more effectively and monitor horse welfare in endurance competitions. Based on previous studies, it was hypothesised that pre-exercise baseline SC and IRTET would be higher in younger or less experienced horses, and that post-exercise variation from baseline would be higher in the top finishers. Results: Salivary cortisol measured in 61 competing at qualifier 40 km and 80 km rides showed an abrupt variation ...
The primary visual cortex of Cetartiodactyls: organization, cytoarchitectonics and comparison with perissodactyls and primates. Cetartiodactyls include terrestrial and marine species, all generally endowed with a comparatively lateral position of their eyes and a relatively limited binocular field of vision. To this day, our understanding of the visual system in mammals beyond the few studied animal models remains limited. In the present study, we examined the primary visual cortex of Cetartiodactyls that live on land (sheep, Père David deer, giraffe); in the sea (bottlenose dolphin, Risso's dolphin, long-finned pilot whale, Cuvier's beaked whale, sperm whale and fin whale); or in an amphibious environment (hippopotam...
Retrobulbar lidocaine injection via the supraorbital fossa is safe in adult horses but produces regionally variable periocular anaesthesia. Injection techniques for retrobulbar anaesthesia are published in horses, but neither safety nor anaesthetic efficacy and duration have been evaluated objectively in vivo. Objective: To characterise the safety and efficacy of one published technique for retrobulbar anaesthesia. Methods: Randomised, controlled descriptive experiment. Methods: Unilateral retrobulbar injection with 10 mL lidocaine (2%) was performed in eight sedated adult mares. Contralateral eyes served as untreated controls. Neurophthalmic parameters, intraocular pressure (IOP), and corneal and periocular sensation were measur...
Horses show individual level lateralisation when inspecting an unfamiliar and unexpected stimulus. Animals must attend to a diverse array of stimuli in their environments. The emotional valence and salience of a stimulus can affect how this information is processed in the brain. Many species preferentially attend to negatively valent stimuli using the sensory organs on the left side of their body and hence the right hemisphere of their brain. Here, we investigated the lateralisation of visual attention to the rapid appearance of a stimulus (an inflated balloon) designed to induce an avoidance reaction and a negatively valent emotional state in 77 Italian saddle horses. Horses' eyes are late...
Safety of a feed additive consisting of a tincture derived from Verbascum thapsus L. (great mullein tincture) for use in all animal species (MANGHEBATI SAS). The tincture derived from L. (great mullein tincture) is intended to be used as a sensory additive in feed for all animal species. The product is a water/ethanol solution, with a dry matter content of ˜ 2.8% and contains on average 0.216% polyphenols including 0.093% flavonoids. According to a previous assessment, the additive was not characterised in full and about 82% of the dry matter fraction remained uncharacterised (representing 2.26% of the tincture). There was also uncertainty on the potential presence of iridoid glycosides in the tincture. Therefore, the Panel on Additives and Prod...
Evaluation of corneal anaesthesia after the application of topical 0.5% bupivacaine, 2% lidocaine and 0.4% oxybuprocaine in normal horses. To compare the corneal anaesthetic effect of 0.5% bupivacaine, 2% lidocaine and 0.4% oxybuprocaine on normal equine eyes. Methods: Prospective, blinded crossover study. Methods: A group of 10 clinically healthy horses. Methods: Corneal sensitivity was determined in each eye by measuring corneal touch threshold (CTT). The study had three phases. Each subject was randomly given one of the three treatments followed by a 72 hour washout period. Every horse received all treatments. Baseline CTT was recorded prior to anaesthetic instillation (T0) then CTT was measured 5 and 10 minutes after (T1 and ...
Effect of Topical Cyclopentolate 1% on Ocular Ultrasonographic Features, Intraocular Pressure, Tear Production, and Pupil Size in Normal Donkeys (Equus Asinus). This study was performed to investigate the effects of cyclopentolate on ultrasonographic parameters of eye structures, intraocular pressure (IOP), tear production, and pupil size in normal donkeys. Sixteen eyes of eight clinically healthy adult donkeys (2-2.5 years old) weighing 295 ± 34 kg (mean ± standard deviation) were used in this study. Cyclopentolate hydrochloride 1% was instilled in a randomly selected eye and the other eye received normal saline drops as a control. The effect of cyclopentolate was evaluated by ultrasonography. Additionally, changes in IOP and tear production were ...
Clinical findings associated with blunt ocular trauma in horses: a retrospective analysis. Identify ocular findings associated with blunt ocular trauma to aid in differentiation from other equine ocular diseases. Methods: Retrospective case-control study. Methods: Medical records of horses at the Equine Clinic Munich-Riem, Munich, Germany and Auburn University, College of Veterinary Medicine were reviewed. Age, sex, breed, laterality, and clinical findings on ophthalmic examination, as well as an observed (confirmed) or unobserved (suspected) history of trauma, were recorded. Statistical analysis was performed to identify any correlation between clinical signs and blunt ocular traum...
