Topic:Ophthalmology
Ophthalmology in horses encompasses the study and treatment of eye disorders and diseases affecting equine species. Equine ophthalmic conditions can range from conjunctivitis and corneal ulcers to more complex issues such as uveitis and cataracts. These conditions can impact a horse's vision and overall well-being. Diagnostic techniques in equine ophthalmology include visual examinations, fluorescein staining, and advanced imaging methods like ultrasonography. Treatment approaches vary depending on the specific condition and may involve medication, surgical intervention, or supportive care. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, pathology, diagnostics, and treatment modalities related to equine ophthalmology.
Multiple Congenital Ocular Anomalies in a silver coat Missouri Fox Trotter stallion. This is the first description of Multiple Congenital Ocular Anomalies (MCOA) in a silver coat Missouri Fox Trotter determined to be heterozygous for the Silver PMEL17 missense mutation associated with MCOA and a silver coat in other breeds. The stallion was treated for meningoencephalitis and bilateral uveitis of unknown origin. A complete ophthalmic examination and ocular ultrasonography were performed. As an incidental finding, the patient exhibited bilateral cystic lesions restricted to the temporal anterior uvea consistent with the Cyst phenotype and was genotyped heterozygous for the Silv...
Neuromuscular blockade with atracurium for ophthalmic surgery in horses-Effects on surgical and anesthetic characteristics and recovery quality. To study the surgical, anesthetic and recovery qualities of horses receiving either a neuromuscular blocking agent (atracurium) or intravenous lidocaine (treatment groups A and L, respectively). Methods: A total of thirty horses presented for ocular surgery were used in this study. Methods: Horses were randomly assigned to receive either atracurium (group A) or a lidocaine constant rate infusion (group L). Surgical quality was graded on a scale from 1 (excellent)-5 (poor). While anesthetized, the heart rate, oxygen saturation and mean arterial blood pressure, and end-expiratory carbon dioxide ...
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...
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...
Ophthalmic Emergencies in the Field. Ophthalmic problems account for up to 20% of emergencies in equine practice. Presenting problems may involve the periocular region, adnexa, or globe. Practitioners must have the experience to restrain horses with painful ocular conditions and the knowledge of how to perform a thorough eye examination. A range of clinical skills is required for the necessary diagnostic tests such as corneal cytology, ultrasound and tonometry, and common standing surgical procedures such as eyelid repair or instillation of a subpalpebral lavage system. Therapy, which may involve frequent administration of multip...
Effect of topical cyclopentolate alone or combined with phenylephrine in healthy horses. Evaluate the effect of repeated doses of topical 1% cyclopentolate hydrochloride alone and in combination with topical 2.5% phenylephrine on pupil diameter (PD), tear production (STT-1), intraocular pressure (IOP), digestive function (gut motility and feces production), and heart rate (HR). Methods: Six healthy mares. Methods: In a prospective, randomized, controlled, and crossover design study, the left eye of six healthy mares was administered 0.2 mL of cyclopentolate alone and in combination with 0.2 mL of phenylephrine. The drugs were administered 3 times a day for 1 day, twice a day fo...
Evaluation of transpalpebral ultrasonographic measurement of optic nerve sheath diameter for indirect assessment of intracranial pressure in anesthetized and standing healthy adult horses. To determine whether an association exists between direct intracranial pressure (ICP) measurement and ultrasonographic measurement of optic nerve sheath diameter (ONSD) in anesthetized and standing horses. Methods: Cross-sectional study performed on a convenience sample of healthy adult horses. Methods: University teaching hospital. Methods: Eight adult horses donated to the University. Enrolled horses were free of abnormalities on physical examination, CBC, neurological evaluation, and ophthalmological examination. Results: Horses were anesthetized in lateral recumbency for placement of an IC...
Topical ophthalmic atropine in horses, pharmacokinetics and effect on intestinal motility. Topical ophthalmic atropine sulfate is an important part of the treatment protocol in equine uveitis. Frequent administration of topical atropine may cause decreased intestinal motility and colic in horses due to systemic exposure. Atropine pharmacokinetics are unknown in horses and this knowledge gap could impede the use of atropine because of the presumed risk of unwanted effects. Additional information could therefore increase safety in atropine treatment. Results: Atropine sulfate (1 mg) was administered in two experiments: In part I, atropine sulfate was administered intravenously and t...
Efficacy and safety of suprachoroidal triamcinolone injection in horses with poorly responsive equine recurrent uveitis. Equine recurrent uveitis (ERU), a chronic, immune-mediated intraocular inflammatory disease, is a common cause of blindness in horses. The severity and recurrent nature of ERU makes it difficult to treat with current therapeutics leading to a poor visual prognosis. The suprachoroidal space (SCS), a potential space between the choroid and sclera surrounding the ocular posterior segment, offers a promising alternative site for drug application to the eye. Corticosteroid administration within this space is hypothesized to be safe and effective at controlling intraocular inflammation, especially i...
Description of a novel ultrasound guided peribulbar block in horses: a cadaveric study. Standing surgery in horses combining intravenous sedatives, analgesics and local anaesthesia is becoming more popular. Ultrasound guided (USG) peribulbar nerve block (PB) has been described in dogs and humans for facial and ocular surgery, reducing the risk of complications versus retrobulbar nerve block (RB). Objective: To describe a technique for USG PB in horse cadavers. Methods: Landmarks and PB technique were described in two equine cadaver heads (Phase 1), with computed tomography (CT) imaging confirming contrast location and spread. In Phase 2, ten equine cadaver heads were randomised t...
First Molecular Confirmation of Equine Ocular Setaria digitata in China. A 5-year-old Mongolian mare (Equus caballus Linnaeus, 1758) was observed to have corneal opacity and excessive ocular discharge. An ophthalmic examination revealed a moving thread-like cylindrical worm in the anterior chamber of the right eye. The parasite was successfully removed surgically. The worm was observed under light microscopy and confirmed as Setaria digitata by 12S rRNA gene amplification and sequencing. Phylogenetic analysis demonstrated similarity with Setaria digitata in the National Center for Biotechnology Information (NCBI) GenBank database isolated from other Asian countries...
Evaluation of equine corneal disease using ultrasound biomicroscopy. To describe the clinical use of ultrasound biomicroscopy (UBM) to evaluate equine corneal disease. Methods: Images were obtained using a 50-MHz probe ultrasound biomicroscopy system (Quantel Aviso) and Clear Scan® probe cover. Six horses with corneal disease were evaluated via UBM for lesion size, lesion depth, and continuity of Descemet's membrane. Horses were sedated and received auriculopalpebral nerve blocks and application of topical anesthetic prior to UBM. Results: Ultrasound biomicroscopy was easily performed in all cases. UBM evaluation of three cases of corneo-limbal squamous cell c...
Subconjunctival enucleation with orbital implant placement in standing horses: 20 cases (2014-2017). To develop a protocol for subconjunctival enucleation and orbital implant placement in standing horses and to document short- and long-term complications, cosmesis, and client satisfaction. Methods: 20 horses with nonneoplastic ocular disease requiring enucleation. Methods: A standardized protocol of surgical suite cleaning, patient preparation, sedation, local nerve blocks, surgical procedure, and postoperative care was performed. Owners were required to provide follow-up information at 1 year after surgery during a phone questionnaire. Additionally, some owners provided follow-up information...
The Fecal Bacterial Microbiota in Horses with Equine Recurrent Uveitis. The objective of this study was to describe and compare the fecal bacterial microbiota of horses with equine recurrent uveitis (ERU) and healthy horses using next-generation sequencing techniques. Fecal samples were collected from 15 client-owned horses previously diagnosed with ERU on complete ophthalmic examination. For each fecal sample obtained from a horse with ERU, a sample was collected from an environmentally matched healthy control with no evidence of ocular disease. The Illumina MiSeq sequencer was used for high-throughput sequencing of the V4 region of the 16S rRNA gene. The relativ...
B-Scan Biometry and Color Doppler Ultrasound Imaging of the Eye in Clinically Normal Donkeys (Equus asinus): Effect of Laterality, Maturity and Gender. Despite the extensive research on ocular ultrasonography, there is paucity of information regarding ocular biometry and color Doppler imaging of the donkey's eye. This study establishes B-scan ocular biometry and color Doppler ultrasonographic reference values in normal donkeys and describes effect of laterality, maturity and gender on ocular biometry and vasculature. Forty (80 eyes) clinically normal immature and mature donkeys of both sexes were included. Transpalpebral ocular ultrasonography was made using a 12-MHz linear transducer. Biometric ocular measurements were made including the ant...
Investigation of the effects of orally administered trazodone on intraocular pressure, pupil diameter, physical examination variables, and sedation level in healthy equids. To investigate the effects of orally administered trazodone on intraocular pressure (IOP), pupil diameter measured in the vertical plane (ie, vertical pupil diameter [VPD]), selected physical examination variables, and sedation level in healthy equids. Methods: 7 horses and 1 pony. Methods: Food was withheld for 12 hours prior to drug administration. After baseline (time 0) sedation scoring, physical examination, and measurement of IOP and VPD, equids received 1 dose (approx 6 mg/kg) of trazodone orally. Examination and measurement procedures were repeated 0.5, 1, 2, 4, 8, 12, and 24 hours aft...
Effects of Intravenous Flunixin Meglumine, Phenylbutazone, and Acupuncture on Ocular Pain Scores in the Horse: A Pilot Study. In this controlled, blinded, randomized block pilot study, the main objective was to evaluate the effectiveness of intravenous flunixin meglumine, phenylbutazone, and acupuncture on ocular pain relief using a multifactorial pain scale in the horse. Four experimental horses underwent corneal epithelial debridement in four sessions, when a randomly selected treatment or a control was used. All horses were pain scored before corneal wounding, then at 18 time points, when 11 parameters were allocated. Differences in the area under the curve of pain scores between the treatment groups were analyzed...
The Impact of Surgical Excision of the Orbital Lacrimal Gland on the Aqueous Tear Production and Ocular Surface Health in Donkeys (Equus asinus). The exact contribution of the orbital lacrimal gland (OLG) is unknown and is still a subject of debate and inconsistency in literature. Currently, there are no detailed studies addressing the influence of the OLG removal on tear production in equines. This study aimed to address the influence of surgical excision of the OLG on aqueous tear production and ocular surface health in donkeys. The study was conducted on six clinically healthy donkeys with no ophthalmic abnormalities. In each donkey, the OLG of the left eye was surgically excised, whereas the right eye was served as a control. Extern...
Effect of multiple head positions on intraocular pressure in healthy, anesthetized horses during hoisting. To evaluate changes in intraocular pressure (IOP) with variable head position in healthy, anesthetized horses in hoisted inversion and to assess the influence of various cofactors (age, sex, body weight, body condition score, and neck length) on IOP changes during hoisting. Methods: Seventeen healthy adult horses without significant ocular abnormalities. Methods: Subjects were administered intravenous xylazine/butorphanol premedication and ketamine/midazolam induction with xylazine/ketamine boluses for anesthetic maintenance. While hoisted, IOP was measured in triplicate for each eye via rebou...
Whole genome sequencing identified a 16 kilobase deletion on ECA13 associated with distichiasis in Friesian horses. 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...
Effect of Topical 1% Tetracaine Hydrochloride on Intraocular Pressure in Ophthalmologically Normal Horses; a Pilot Study. The aim of this study was to evaluate the effect of topical 1% tetracaine hydrochloride on the intraocular pressure (IOP) in ophthalmologically normal horses. Thirty eyes of 15 clinically normal horses were used for this study. The animals were randomly assigned to two groups (treatment and control). Prior to the instillation of 1% tetracaine or placebo, the baseline IOPs (T0) of each animal were recorded in both groups. Then one drop of tetracaine was instilled randomly into one eye of each horse in the treatment group (8 horses). In the control group (7 horses), one drop of artificial tear w...
Changes in antimicrobial resistance patterns of ocular surface bacteria isolated from horses in the UK: An eight-year surveillance study (2012-2019). To identify temporal changes in antimicrobial resistance of ocular surface bacteria isolated from clinically symptomatic equine eyes in the South West of the UK. Methods: Retrospective. Methods: Clinical and laboratory records of horses treated for suspected bacterial ocular surface disease (ulcerative and non-ulcerative) at a single facility between January 2011 and December 2019 were reviewed. Cases were included if they underwent ocular surface sampling, aerobic bacterial culture, and antimicrobial susceptibility testing. Cases were split into two time periods based on when sampling occurre...
Intraocular pressure following four different intravenous sedation protocols in normal horses. Intravenous sedation is frequently necessary for ophthalmic examination in horses. Common sedation protocols have not been directly compared in terms of relative intraocular pressure (IOP) reduction, duration of IOP reduction and time to maximum IOP reduction. Objective: To compare the effects of standing sedation protocols on IOP. Methods: Randomised cross-over experiment. Methods: Twelve healthy horses received four intravenous sedation protocols with a 48 hours washout: 0.5 mg/kg xylazine and 0.01 mg/kg butorphanol (SED1); 10 µg/kg detomidine and 0.01 mg/kg of butorphanol (SED2); 10 ...
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...
Serum albumin and total protein concentration in the tear film of horses with healthy or diseased eyes. To determine total protein content (TPC) and serum albumin levels in the tears of horses with healthy or diseased eyes. Methods: Forty-two horses with healthy eyes and 11 horses with unilateral (n = 10) or bilateral (n = 1) ocular disease. Methods: Each eye underwent an ophthalmic examination including detailed conjunctivitis scoring and tear collection with Schirmer strips. TPC and serum albumin levels were quantified in tear samples and compared among healthy eyes, affected eyes, and contralateral unaffected eyes. The impact of the following variables on lacrimal protein levels were asse...
Comparison of two rebound tonometers in healthy horses. To obtain a reference range for evaluation of intraocular pressure (IOP) in horses using Tonovet Plus , to compare the IOP readings obtained with Tonovet and Tonovet Plus , and to evaluate the repeatability of readings. Unassigned: Intraocular pressure of 30 client-owned horses (60 eyes) with no signs of illness or ocular disease was evaluated using Tonovet and Tonovet Plus rebound tonometers. Horses' mean age was 10.7 (range 6-17) years. Triplicate measurements were performed without using sedatives or local anesthetics, with minimal restraint. Results: Calculated reference intervals (the CLS...
Ocular disease in horses with confirmed ocular or central nervous system Borrelia infection: Case series and review of literature. To describe the clinical presentation, treatment, and clinical outcome of horses with ocular disease and evidence of systemic or ocular Lyme disease. Methods: Five horses met the inclusion criteria of ocular disease with evidence of B burgdorferi present in ocular or CNS tissues. Methods: The goal of this study was to describe the clinical presentation and progression of ocular disease when associated with ocular or CNS B burgdorferi infection in horses. A retrospective review of medical records was performed on horses admitted for ocular disease with evidence of B burgdorferi infection bet...