Topic:Blindness
Blindness in horses is a condition characterized by the partial or complete loss of vision, which can result from various causes such as genetic disorders, trauma, infections, or degenerative diseases. It affects a horse's ability to navigate its environment and can impact its behavior and performance. Common causes of blindness in horses include equine recurrent uveitis, cataracts, and retinal detachment. Diagnosis typically involves thorough ophthalmic examinations and may require advanced imaging techniques. This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, diagnosis, management, and implications of blindness in equine health and welfare.
Treatment of Progressive Scleromalacia Perforans by Tectonic Enhancement With Lyophilized Equine Pericardium. To describe the off-label use of lyophilized equine pericardium for tectonic enhancement of the sclera in a case of progressive scleromalacia perforans. Methods: An 82-year-old woman with a history of varicella zoster virus sclerokeratitis presented with a progressively expanding scleral thinning at the superonasal quadrant of the anterior sclera of her left eye. The eye was blind because of intractable glaucoma. To avoid perforation of the exposed choroid, a single layer of lyophilized equine pericardium was sutured over the scleral perforation. After performing a conjunctival peritomy in the...
Resolution of neurologic signs presumed to be associated with hyperammonemia in 2 endurance horses. This case report describes 2 endurance horses with non-hepatic hyperammonemia. The animals were competing in a 160-km endurance competition in extreme heat conditions and were presented for obtundation. One of the horses also had evidence of blindness. The blood ammonia concentration was elevated (196 μmol/L and 249 μmol/L) and both horses improved following treatment with intravenous fluids and supportive care. These are the first documented cases of clinical signs presumed to be associated with hyperammonemia in endurance horses. Despite the severity of the clinical presentation, both hors...
Whole-genome sequencing identifies missense mutation in GRM6 as the likely cause of congenital stationary night blindness in a Tennessee Walking Horse. The only known genetic cause of congenital stationary night blindness (CSNB) in horses is a 1378 bp insertion in TRPM1. However, an affected Tennessee Walking Horse was found to have no copies of this variant. Objective: To identify the genetic cause for CSNB in an affected Tennessee Walking Horse. Methods: Case report detailing a whole-genome sequencing (WGS) approach to identify a causal variant. Methods: A complete ophthalmic exam, including an electroretinogram (ERG), was performed on suspected CSNB-affected horse. WGS data were generated from the case and compared with data from seven ot...
Genetics of Equine Ocular Disease. Horses perform in a variety of disciplines that are visually demanding, and any disease impacting the eye has the potential to threaten vision and thus the utility of the horse. Advances in equine genetics have enabled the understanding of some inherited ocular disorders and ocular manifestations and are enabling cross-species comparisons. Genetic testing for multiple congenital ocular anomalies, congenital stationary night blindness, equine recurrent uveitis, and squamous cell carcinoma can identify horses with or at risk for disease and thus can assist in clinical management and breeding dec...
Leptospiral antibody prevalence and surgical treatment outcome in horses with Equine Recurrent Uveitis (ERU) in Switzerland. 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 ...
The prevalence of uveitis in a population of donkeys in the UK. Uveitis is reported to be a leading cause of blindness in horses. Little work has been undertaken to date to investigate whether donkeys are affected by a similar disease prevalence. Objective: To investigate the disease prevalence of uveitis in a population of donkeys in the UK. Methods: Descriptive observational study. Methods: An ophthalmic examination was performed on each donkey, in a darkened stable. Each donkey underwent slit lamp biomicroscopy, and direct and/or indirect ophthalmoscopy. Fluorescein staining, STT1 and IOPs were measured when deemed clinically necessary. Pharmacologica...
Mortality and Operational Attributes Relative to Feral Horse and Burro Capture Techniques Based on Publicly Available Data From 2010-2019. Management of excessive feral horse (Equus ferus caballus) and burro (Equus asinus) populations in the United States and globally has been a controversial subject for decades. I reviewed all available US federal feral horse and burro daily gather reports from 2010 to 2019 to extract equine species, technique (bait trapping or helicopter gathering), reason (emergency or other), number gathered, number of mortalities, and mortality attributes (acute or chronic/pre-existing condition, specific cause). I found 70 reports (bait trapping burros n = 10, bait trapping horses n = 24, helicopter gathe...
Genetic investigation of equine recurrent uveitis in Appaloosa horses. Equine recurrent uveitis (ERU) is characterized by intraocular inflammation that often leads to blindness in horses. Appaloosas are more likely than any other breed to develop insidious ERU, distinguished by low-grade chronic intraocular inflammation, suggesting a genetic predisposition. Appaloosas are known for their white coat spotting patterns caused by the leopard complex spotting allele (LP) and the modifier PATN1. A marker linked to LP on ECA1 and markers near MHC on ECA20 were previously associated with increased ERU risk. This study aims to further investigate these loci and identify a...
Persistent Bilateral Mydriasis Associated With a Pituitary Adenoma in a Horse. Severe bilateral mydriasis and bilaterally decreased vision were observed in a 23-year-old crossbred warmblood gelding with a history of pituitary pars intermedia dysfunction. Ten years after the onset of clinical signs, it was killed humanely because of worsening of clinical signs and loss of therapeutic responsiveness. Postmortem examination of the head was performed to confirm the suspected pituitary neoplasm and to investigate secondary oculomotor lesions. Pathomorphologic examination revealed an expansile space-occupying pituitary adenoma and degenerative changes in the preganglionic ocul...
Autoimmune diseases affecting skin melanocytes in dogs, cats and horses: vitiligo and the uveodermatological syndrome: a comprehensive review. Autoimmune dermatoses targeting melanocytes have gained attention in human medicine due to their progressive nature and the social impact suffered by affected individuals. In veterinary medicine, vitiligo and the uveodermatological syndrome are the two autoimmune diseases that are known to affect skin melanocytes.In the first part of this article, we will review the signalment, clinical signs, histopathology and the treatment outcome of vitiligo in dogs, cats and horses; where pertinent, we compare the animal diseases to their human homologue. In a similar fashion, the information on the uveod...
[Intravitreal injection of low-dose gentamicin for the treatment of ERU-affected horses]. Aim of the study was the retrospective evaluation regarding vision and recurrence in equine recurrent uveitis (ERU)-affected horses treated by intravitreal low-dose gentamicin injection in Tierklinik Alt Sammit during the years 2006-2013. Methods: The study included 50 equine patients (61 ERU-affected eyes) of different age and breed with different stages of ERU. The solution for the injection contained 4.0 mg sterile gentamicin per eye. The injection was performed according to the procedure described by Pinard et al. in 2005 under general anaesthesia in lateral recumbency of the patient and...
Equine-related eye injury: a case report of globe rupture and vision loss in a post-stroke hippotherapy patient. Hippotherapy has recently emerged as a horse-based rehabilitative therapy to improve balance, coordination, and strength in patients with a wide range of medical conditions. Although several studies have demonstrated its effectiveness in restoring balance and gait in patients who have suffered cerebrovascular accidents (CVA), few studies have reported on adverse events associated with the treatment. Methods: This case report describes a female post-stroke patient who fell from a horse during a hippotherapy session. She suffered a closed right zygomaticomaxillary complex fracture and ruptured g...
First description of a fatal equine infection with Halicephalobus gingivalis in Portugal. Relevance for public health. Halicephalobus gingivalis is a small saprophytic rhabditid nematode, represented only by females with a typical rhabditoid oesophagus and one egg in the uterus, capable of infecting vertebrates. This opportunistic parasite present in the soil, manure and decaying humus, is thought to penetrate through previous injuries to the mouth, eyes and skin of horses and migrate to various organs. The brain is one such organ, where the females lay their eggs, leading to malacia and causing a sudden onset of neurological signs, such as anorexia, ataxia, urinary incontinence, blindness, decreased menace an...
Prevalence of owner-reported ocular problems and veterinary ocular findings in a population of horses aged ≥15 years. Previous studies suggest that ocular disease is common among aged horses but owners may fail to identify or underestimate their clinical relevance. Objective: To document the prevalence of owner-reported ocular disease in horses aged ≥15 years. In a subset of these horses, to document ophthalmic findings from veterinary examination and compare with owner-reported ocular disease, and to determine risk factors for veterinary ophthalmic findings. Methods: Cross-sectional study. Methods: Owners of aged horses completed a survey on management, clinical signs and medical history. Risk factors for ...
Paranasal sinus cysts in the horse: Complications related to their presence and surgical treatment in 37 cases. Paranasal sinus cysts (PSC) are a common cause of equine secondary sinusitis. The outcome and associated complications have not been frequently reported. Objective: To review the associated clinical signs, associated morbidities and outcomes of horses treated for PSC. Methods: Retrospective multicentre case series. Methods: Retrospective analysis of case records and telephone follow up survey. Results: Subjects were 37 horses 1-24 years old that were presented with nasal discharge (n = 31), facial swelling (n = 25) and epiphora (n = 19). Radiography and computed tomography allowed identificati...
Immune Relevant Models for Ocular Inflammatory Diseases. Ocular inflammatory diseases, such as dry eye and uveitis, are common, painful, difficult to treat, and may result in vision loss or blindness. Ocular side effects from the use of antiinflammatory drugs (such as corticosteroids or nonsteroidal antiinflammatories) to treat ocular inflammation have prompted development of more specific and safer medications to treat inflammatory and immune-mediated diseases of the eye. To assess the efficacy and safety of these new therapeutics, appropriate immune-relevant animal models of ocular inflammation are needed. Both induced and naturally-occurring mode...
First Blindness Cases of Horses Infected with Setaria Digitata (Nematoda: Filarioidea) in the Republic of Korea. Ocular setariases of cattle were reported but those of equine hosts have never been reported in the Republic of Korea (Korea). We found motile worms in the aqueous humor of 15 horses (Equus spp.) from 12 localities in southern parts of Korea between January 2004 and November 2017. After the affected animals were properly restrained under sedation and local anesthesia, 10 ml disposable syringe with a 16-gauge needle was inserted into the anterior chamber of the affected eye to successfully remove the parasites. The male worm that was found in 7 of the cases showed a pair of lateral appendages n...
Uveal myxoid leiomyosarcoma in a horse. A uveal leiomyosarcoma of a horse is reported. There are few published reports of intraocular tumors in horses. Intraocular tumors challenge animal welfare by causing uveitis, glaucoma, and loss of vision. Knowledge regarding treatment of intraocular tumors with globe preservation is sparse, and further investigations on this topic are required.
Kinematic discrimination of ataxia in horses is facilitated by blindfolding. Agreement among experienced clinicians is poor when assessing the presence and severity of ataxia, especially when signs are mild. Consequently, objective gait measurements might be beneficial for assessment of horses with neurological diseases. Objective: To assess diagnostic criteria using motion capture to measure variability in spatial gait-characteristics and swing duration derived from ataxic and non-ataxic horses, and to assess if variability increases with blindfolding. Methods: Cross-sectional. Methods: A total of 21 horses underwent measurements in a gait laboratory and live neurolog...
Equine recurrent uveitis in western Canadian prairie provinces: A retrospective study (2002-2015). The objectives of this study were to determine the demographics of horses with equine recurrent uveitis (ERU) presenting to the Western College of Veterinary Medicine and to describe and compare the prognosis of ERU in the Appaloosa with that in other breeds. Horses diagnosed with ERU by a veterinary ophthalmologist between 2002 and 2015 were included. Eye lesions were classified as mild, moderate, or severe based on clinical manifestations. Breed, age, severity, blindness, and final outcome were evaluated. Thirty-two horses fit the inclusion criteria; 62.5% were Appaloosas. Mean age at presen...
The refractive state of the eye in Icelandic horses with the Silver mutation. The syndrome Multiple Congenital Ocular Anomalies (MCOA) is a congenital eye disorder in horses. Both the MCOA syndrome and the Silver coat colour in horses are caused by the same missense mutation in the premelanosome protein (PMEL) gene. Horses homozygous for the Silver mutation (TT) are affected by multiple ocular defects causing visual impairment or blindness. Horses heterozygous for the Silver mutation (CT) have less severe clinical signs, usually cysts arising from the ciliary body iris or retina temporally. It is still unknown if the vision is impaired in horses heterozygous for the Sil...
Blindness associated with nasal/paranasal lymphoma in a stallion. A 29-year-old stallion presented with bilateral blindness following the chronic purulent nasal drainage. The mass occupied the right caudal nasal cavity and right paranasal sinuses including maxillary, palatine and sphenoidal sinuses, and the right-side turbinal and paranasal septal bones, and cribriform plate of ethmoid bone were destructively replaced by the mass growth. The right optic nerve was invaded and involved by the mass, and the left optic nerve and optic chiasm were compressed by the mass which was extended and invaded the skull base. Histologically, the optic nerves and optic chia...
Transnasal, Endoscopically Guided Skull-Based Surgery by Pharyngotomy for Mass Removal from the Sphenopalatine Sinus in a Horse. To report a transnasal, endoscopically guided ventral surgical approach for accessing the cranial and caudal segments of the sphenopalatine sinus for mass removal in a horse. Methods: Case report. Methods: Adult horse with acute onset blindness referable to a soft tissue mass within the sphenopalatine sinus. Methods: A 7-year-old Warmblood gelding presented with a history of running into a fence and falling. No neurologic signs were identified at initial examination but acute blindness was noted 3 weeks later. On computed tomography (CT) the sphenopalatine sinus was filled with a large homogen...
Phage Therapy Is Effective in a Mouse Model of Bacterial Equine Keratitis. Bacterial keratitis of the horse is mainly caused by staphylococci, streptococci, and pseudomonads. Of these bacteria, Pseudomonas aeruginosa sometimes causes rapid corneal corruption and, in some cases, blindness. Antimicrobial resistance can make treatment very difficult. Therefore, new strategies to control bacterial infection are required. A bacteriophage (phage) is a virus that specifically infects and kills bacteria. Since phage often can lyse antibiotic-resistant bacteria because the killing mechanism is different, we examined the use of phage to treat horse bacterial keratitis. We isol...
Electroretinographic changes after intravenous lipid emulsion therapy in a dog and a foal with ivermectin toxicosis. This case report describes ivermectin-induced blindness in a dog and a foal with normal ophthalmic fundic examinations and attenuated electroretinography (ERG). Subsequent recovery in ERG was noted following intravenous lipid emulsion (ILE) therapy. A dog and a foal were evaluated for ivermectin-induced blindness. Clinical signs included dull mentation, absent pupillary light reflexes (PLRs), and absent menace on presentation. The animals had normal fundoscopic examinations; however, in both cases ERG was consistent with neurosensory retinal dysfunction. Following ILE therapy for ivermectin to...
Redundant contribution of a Transient Receptor Potential cation channel Member 1 exon 11 single nucleotide polymorphism to equine congenital stationary night blindness. Congenital stationary night-blindness (CSNB) is a recessive autosomal defect in low-light vision in Appaloosa and other horse breeds. This condition has been mapped by linkage analysis to a gene coding for the Transient Receptor Potential cation channel Member 1 (TRPM1). TRPM1 is normally expressed in the ON-bipolar cells of the inner nuclear layer of the retina. Down-regulation of TRPM1 expression in CSNB results from a transposon-like insertion in intron 1 of the TRPM1 gene. Stop transcription signals in this transposon significantly reduce TRPM1 primary transcript levels in CSNB horses. Thi...
Ophthalmologic Disorders in Aged Horses. Ocular abnormalities are a common finding in aged horses. Although these seldom cause overt visual deficits detected by their owners, they can be a source of chronic or acute discomfort so early detection, and treatment when available, is essential. Some of these abnormalities are specific to old horses, whereas others are a result of ongoing disease or inflammation that started earlier in life but that becomes more evident when the damage sustained to the eye is advanced. If vision is significantly affected, consideration of human safety and animal welfare is paramount.
Severe hyponatraemia in foals: clinical findings, primary diagnosis and outcome. To evaluate severe hyponatraemia in foals presenting as medical emergencies to an intensive care unit (ICU) in order to determine the prevalence, clinical findings, primary diagnosis and outcome. Methods: Retrospective case study of records from Thoroughbred foals aged less than 3 months presenting to an ICU as medical emergencies in 2002-12; foals with severe hyponatraemia (serum sodium <122 mmol/L) on admission laboratory data were identified. Data retrieved included signalment, clinical findings, laboratory results, primary diagnosis, treatment and outcome. Results: Severe hyponatraemia w...
Ocular Pathology. Although not comprehensive of all ocular conditions in the equine species, this article concentrates on various ophthalmic conditions observed in the horse where laboratory diagnostics are recommended. The importance of laboratory diagnostic testing cannot be underestimated with equine ophthalmic disease. In many cases, laboratory diagnostics can aid in obtaining an early diagnosis and determining appropriate therapy, which in turn, can provide a better prognosis. In unfortunate cases where ocular disease results in a blind, painful eye necessitating enucleation, light microscopic evaluation i...
Prognosis and impact of equine recurrent uveitis. Equine recurrent uveitis (ERU) is a leading cause of vision loss in horses. Objective: To assess the prognosis and impact of ERU on affected horses and their owners by evaluating the signalment, treatment and outcome (including the loss of use, vision assessment and economic loss). Methods: Retrospective impact study. Methods: Medical records of horses presenting to the North Carolina State University Veterinary Health Complex (NCSU-VHC) with ERU between 1999 and 2014 were reviewed. Signalment, clinical signs, ophthalmic examination findings, treatments and outcomes were evaluated. Owner quest...