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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.
Fungal polymerase chain reaction testing in equine ulcerative keratitis. 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...
Association of height, body weight, age, and corneal diameter with calculated intraocular lens strength of adult horses. To determine whether differences exist in the calculated intraocular lens (IOL) strengths of a population of adult horses and to assess the association between calculated IOL strength and horse height, body weight, and age, and between calculated IOL strength and corneal diameter. Methods: 28 clinically normal adult horses (56 eyes). Methods: Axial globe lengths and anterior chamber depths were measured ultrasonographically. Corneal curvatures were determined with a modified photokeratometer and brightness-mode ultrasonographic images. Data were used in the Binkhorst equation to calculate the ...
Predictability of visual perturbation during locomotion: implications for corrective efference copy signaling. 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...
Ocular disease in working horses in Ethiopia: a cross-sectional study. Ocular disease is a frequent finding in working horses. This study aimed to estimate the prevalence and types of ocular pathology, and explore risk factors potentially associated with disease within a population of working horses in Ethiopia. In total, 1049 horses were selected from horses attending clinics run by the Society for Protection of Animals Abroad (SPANA). Each had an ophthalmic examination conducted under field conditions using a pen-torch. All owners completed a short questionnaire. The prevalence of ocular abnormalities was 23.5 per cent (95 per cent confidence interval (CI) 18.0...
Light microscopic evaluation and scanning electron microscopic analysis of horse eyes following deep anterior lamellar keratectomy. OBJECTIVE To describe the technique of deep anterior lamellar keratoplasty (DALK) with Descemet's membrane (DM) exposure in horse eyes. Also, to compare the efficacy and safety of viscodissection and big-bubble techniques for DALK. ANIMALS STUDIED Thirty-four ex vivo horse eyes. PROCEDURE Deep anterior lamellar keratoplasty was performed in 34 ex vivo horse eyes. Two groups (Group V--viscodissection--2% sodium hyaluronate; Group A--air--big-bubble) of 17 eyes were studied. Other than the substance used, the surgical technique was similar for both groups. Nonperforated eyes were submit...
Benign intraocular teratoid medulloepithelioma causing glaucoma in an 11-year-old Arabian mare. An 11-year-old Arabian mare was presented for investigation of a visible, pale-colored intraocular mass in the right eye. Results: An intraocular mass was detected clinically and ultrasonographically as originating from the superior temporal quadrant of the ciliary body and iris and causing secondary glaucoma. The echodense mass was occupying the majority of the vitreous chamber and extended into the anterior chamber. The left eye appeared normal. Results: Enucleation was recommended for therapeutic and diagnostic purposes. No adjuvant treatment was given. Histopathological examination demonst...
Equine keratomycoses in California from 1987 to 2010 (47 cases). Equine keratomycosis in the western USA has received little study, probably owing to its low prevalence. Objective: To determine clinical features, predominant fungal isolates, treatment modalities and outcomes of horses with keratomycosis in California and compare these with results from different geographic regions. Methods: Records of horses presented to the University of California-Davis Veterinary Medical Teaching Hospital (UCD-VMTH) with confirmed keratomycosis between 1987 and 2010 were reviewed for this retrospective study. Information retrieved from the record included background, oph...
Ocular abnormalities in healthy Standardbred foals. To determine the prevalence and describe ocular abnormalities in healthy Standardbred foals within 48 h of birth. Methods: One hundred and two neonatal foals. Methods: All foals had an unassisted delivery. On the basis of physical examination and the results of hematological and biochemical parameters, all foals were unaffected by systemic diseases. A complete ophthalmic examination was performed within 48 h of birth. Foals with ocular hemorrhages were re-examined weekly until the abnormalities were resolved. Results: 65/102 (63.7%) foals did not show ocular abnormalities, while in 37/102 (36....
A pilot study on the corneal curvatures and ocular dimensions of horses less than one year of age. 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...
Ocular manifestations of a metastatic adenocarcinoma in a horse. A 10-year-old German Warmblood gelding was referred to the Equine Department of the Vetsuisse Faculty, University of Zurich, Switzerland, for an iris mass OD, lethargy, intermittent fever, and coughing. Ophthalmic examination revealed a 7 × 9 mm raised, fleshy, whitish to pinkish, vascularized iris mass at the 2 o`clock position OD. Fundic examination showed multifocal round, brown to black, slightly raised lesions with indistinct margins and a surrounding hyperreflective zone OU. Physical examination revealed a temperature of 39.2 °C, sinus tachycardia, preputial and ventral edema, and an e...
Lateral vision in horses: a behavioral investigation. This study investigated lateral vision in horses (Equus caballus) for the first time from a behavioral point of view. Three horses were tested using a novel experimental design to determine the range of their lateral and caudolateral vision with respect to stimulus detection and discrimination. Real-life stimuli were presented along a curvilinear wall in one of four different positions (A, B, C, D) and one of two height locations (Top, Bottom) on both sides of the horse. To test for stimulus detection, the correct stimulus was paired against a control; for stimulus discrimination, the correct ...
Diode laser endoscopic cyclophotocoagulation in the normal equine eye. To determine the clinical and histologic effects of diode endoscopic cyclophotocoagulation (ECP) in the phakic equine eye. Methods: Phase I: 10 equine cadaver eyes. Phase II: four normal adult horses. Methods: Phase I: ECP probe angle of reach (AR) was determined. Multiple ECP energy levels: 0.75, 0.90, 1.05, 1.20, 1.35, 1.50 J, and the resulting visible and histologic ciliary process changes were evaluated. Phase II: Ocular quadrants were treated with ECP at 0.90, 1.14, 1.38 J, and a control. The contralateral eye underwent a sham operation. Tissue changes (clinical and histologic) were evalu...
Equine subepithelial keratomycosis. To describe clinical findings in equine subepithelial keratomycosis (SEK). Methods: Retrospective medical records study. Methods: Medical records of horses that had subepithelial keratomycosis (SEK) at the University of Florida Veterinary Medical Center from 2007 to 2011 were reviewed. Methods: Data collected from the medical records included signalment, clinical descriptions of ocular lesions, diagnostic techniques, and therapeutic outcomes. Results: Twenty-one horses, consisting of three Quarter horse geldings, two Morgan geldings, one Morgan mare, two Arabian mares, three Arabian geldings, ...
Extraocular lymphoma in the horse. To describe the clinical findings and prognosis for extraocular lymphoma in the horse. Methods: Retrospective medical records study of horses diagnosed with third eyelid, corneoscleral, conjunctival, and/or eyelid lymphoma from multiple academic and private veterinary institutions. Data collected from the medical records included signalment, clinical descriptions of the extraocular lesions, treatment, and treatment outcomes. Nonparametric statistical analysis was performed with Fischer's exact tests. Results: Extraocular lymphoma involving the eyelid, third eyelid, cornea, sclera, and/...
Refractive state of the Spanish Thoroughbred horse: a comparison with the Crossbred horse. To assess the refractive state of the equine eye utilizing retinoscopy. To compare the refractive state of Spanish Thoroughbred horses with the refractive state of Crossbred horses. Methods: The refractive state of 135 horses (264 eyes) was assessed utilizing streak retinoscopy. Two perpendicular meridians were examined in order to assess astigmatism at a working distance of approximately 67 cm. A group of 81 Spanish Thoroughbred horses was compared with a group of 54 Crossbred horses. Cyclopentolate ophthalmic solution was instilled in the eyes of a group of 18 horses to determine if accommod...
Electrophysiological studies in American Quarter horses with neuroaxonal dystrophy. Neuroaxonal dystrophy (NAD) is a disease characterized by the sudden onset of neurologic signs in horses ranging from 4 to 36 months of age. Equine degenerative myeloencephalopathy (EDM), a disease that has been associated with low vitamin E concentrations, is considered a more advanced form of NAD. The objective of this report is to describe the electrophysiological features of NAD/EDM in American Quarter horses (QHs). HORSES: Six NAD/EDM-affected QHs and six unaffected QHs were evaluated by ophthalmic examination and electroretinography. Five of the NAD/EDM-affected QH and five unaffected QH...
Optimal management of equine keratomycosis. Keratomycosis in the horse exists in several unique clinical forms. This paper discusses the diagnosis and clinical management of keratomycosis in the horse associated with tear film instability, epithelial keratopathy, subepithelial infiltrates, superficial and deep ulcers, plaques, melting ulcers, descemetoceles, iris prolapse, and stromal abscesses. Prompt diagnosis and aggressive treatment of equine keratomycosis can make a major difference in the maintenance of a cosmetic and visual eye.
Equine keratomycosis in Japan. To describe the incidence, clinical progress, visual outcome, and laboratory findings of equine keratomycosis in Japan. Methods: Retrospective study of the medical records of horses clinically and mycologically diagnosed with keratomycosis at the Equine Hospitals of the Japan Racing Association from 2005 to 2011. Results: The diagnosis of keratomycosis was confirmed in eight horses (40.0% of the 20 horses with infectious keratitis from which fungi and/or bacteria were isolated). Fungi recovered from corneal swabs were identified as Aspergillus flavus (4), Aspergillus niger (1), Fusarium sol...
Ophthalmology in equine ambulatory practice. Equine practitioners examine patient eyes on a daily basis. Indications range from inspection of normal anatomy to treatment of traumatized eyes to workups of sight threatening inflammatory or neoplastic ocular conditions. Assessment of equine eyes requires practitioners to take time to create a good "exam room" in the field and administer appropriate restraint, sedation and/or regional anesthesia to facilitate thorough examination. Accurate diagnosis and treatment of equine eye problems requires skill in ocular surface staining and cytology, and basic proficiency in standing surgery. Expertis...
Third eyelid dermoid in a horse. An 8-year-old Gypsy Vanner gelding presented to the University of Florida Ophthalmology service for the evaluation of chronic, recurrent corneal ulcers behind the third eyelid of the right eye. On ophthalmic examination, a cluster of aberrant hairs was identified growing along the margin of the third eyelid. This portion of third eyelid was surgically excised, and histopathology identified the haired tissue as a dermoid. Chronic keratitis secondary to a third eyelid dermoid was diagnosed, and excision appeared curative at 6 months post-operative follow-up.
The long-term effects of semiconductor diode laser transscleral cyclophotocoagulation on the normal equine eye and intraocular pressure(a). 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...
Antibodies to a novel leptospiral protein, LruC, in the eye fluids and sera of horses with Leptospira-associated uveitis. Screening of an expression library of Leptospira interrogans with eye fluids from uveitic horses resulted in identification of a novel protein, LruC. LruC is located in the inner leaflet of the leptospiral outer membrane, and an lruC gene was detected in all tested pathogenic L. interrogans strains. LruC-specific antibody levels were significantly higher in eye fluids and sera of uveitic horses than healthy horses. These findings suggest that LruC may play a role in equine leptospiral uveitis.
Characterization of cytokines associated with Th17 cells in the eyes of horses with recurrent uveitis. Equine recurrent uveitis (ERU) is a spontaneous disease that is the most common cause of blindness in horses, affecting up to 15% of the horse population. Th17 cells are a major cell population driving the pathogenesis in several mouse models of autoimmune inflammation, including experimental autoimmune uveitis. The purpose of this study is to investigate the role a Th17 cell-mediated response plays in the pathogenesis of ERU. Methods: Banked, Davidson's-fixed equine globes histopathologically diagnosed with ERU (n = 7) were compared immunohistochemically with healthy control globes (n = 7). I...
Examination of the anterior uveoscleral pathway in domestic species. To investigate the uveoscleral (US) pathway in the normal eyes of four domestic spp.: the cat, pig, cow and horse by examining the comparative anatomical structure of anterior US pathway. Methods: Four cats, ten pigs, four cows, eight horses. Methods: Formalin-preserved specimens from anterior uveas of the cat, pig, cow and horse were embedded and serially sectioned sagittally and tangentially and stained with H&E, Masson's trichrome, smooth muscle actin immunolabel, or elastin stain. Results: Spaces between the endings of the outer anterior ciliary body musculature (CBM) formed avenues fo...
Ophthalmic lesions in neonatal foals evaluated for nonophthalmic disease at referral hospitals. 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...
Phacoemulsification and implantation of foldable +14 diopter intraocular lenses in five mature horses. Presently, intraocular lenses (IOLs) are not routinely implanted after equine cataract surgery. Subsequently, horses are visual but markedly farsighted (hyperopic). This report describes the surgical results and visual status after phacoemulsification and implantation of IOLs in mature horses with spontaneous cataracts. Six eyes of 5 mature horses underwent phacoemulsification and implantation of a +14 diopter (D) foldable IOL. Recheck ocular examinations were performed at 1, 4 and 24 weeks post operatively. Refractive error was recorded at 4 weeks post operatively. Visual status, refractive e...
Multiple congenital ocular anomalies in Icelandic horses. Multiple congenital ocular anomalies (MCOA) syndrome is a hereditary congenital eye defect that was first described in Silver colored Rocky Mountain horses. The mutation causing this disease is located within a defined chromosomal interval, which also contains the gene and mutation that is associated with the Silver coat color (PMEL17, exon 11). Horses that are homozygous for the disease-causing allele have multiple defects (MCOA-phenotype), whilst the heterozygous horses predominantly have cysts of the iris, ciliary body or retina (Cyst-phenotype). It has been argued that these ocular defects...
Evaluation of the Perkins handheld applanation tonometer in horses and cattle. The objective of this study was to evaluate and validate the accuracy of the Perkins handheld applanation tonometer for measuring intraocular pressure (IOP) in horses and cattle. Both eyes of 10 adult horses and cattle were evaluated in a postmortem study. The eyes from 10 clinically normal adult horses and cattle were also examined after bilateral auriculopalpebral nerve block and topical anesthesia for an in vivo study. IOP was measured postmortem using direct manometry (measured with an aneroid manometer) and tonometry (measured with a Perkins handheld applanation tonometer). The correlatio...
Mortierella wolfii keratomycosis in a horse. To describe a case of superficial keratomycosis caused by Mortierella wolfii (M. wolfii) in a horse. Methods: A thoroughbred filly was presented with painful right eye of 2 days' duration. A superficial corneal ulcer was observed ventrally together with multifocal punctuate opacities axially. Samples were collected by swabbing and scraping the ulcerated lesion and submitted for microbiologic and cytologic examination. Results: Microscopic evaluation of debrided corneal tissue revealed the presence of nonseptate fungal hyphae, and culture of a corneal swab yielded fungal growth. Medical treat...
