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.
Complications of ophthalmic surgery in the horse. Corneal transplantation, amniotic membrane transplantation, phacoemulsification cataract extraction, and laser glaucoma therapy are routine ophthalmic surgical procedures in horses. This article discusses the indications, techniques, and postoperative complications of these and other ophthalmic surgical procedures in horses. Meticulous and accurate anatomic repair can minimize postoperative complications to maintain positive visual outcomes in ophthalmic surgery of the horse.
Equine Multiple Congenital Ocular Anomalies maps to a 4.9 megabase interval on horse chromosome 6. 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...
Ocular distribution and toxicity of intravitreal injection of triamcinolone acetonide in normal equine eyes. To determine ocular distribution and toxicity of a single injection of intravitreal triamcinolone acetonide (TA) in normal horses. Methods: Six adult horses, donated to North Carolina State University. Methods: Six horses were injected intravitreally with either 10, 20, or 40 mg (n = 2 each) of TA. The opposite eye of each horse was injected with balanced salt solution (BSS). Ocular toxicity was assessed by biomicroscopy, tonometry, indirect ophthalmoscopy, and electroretinogram. Aqueous humor (AH), vitreous humor (VH), and plasma samples were collected. Horses were euthanized 7 or 21 days aft...
Blindness, optic atrophy and sinusitis in the horse. The case histories described each presented with a visual deficit, varying from permanent total blindness with ophthalmoscopic evidence of optic atrophy to variable and transient visual disturbances, including occasional blindness, but with absence of ophthalmoscopic or any other ocular abnormality. Methods: Three horses of widely different age and type, but all with an original history of upper respiratory tract infection. Methods: All three cases were examined by a specialist veterinary ophthalmologist. In addition, magnetic resonance imaging (MRI) and, where possible, postmortem and histopa...
Photodynamic therapy for the treatment of periocular squamous cell carcinoma in horses: a pilot study. Local photodynamic therapy (PDT) is a novel cancer therapy in veterinary ophthalmology. A prospective pilot study seeking to demonstrate proof of principle and safety for the treatment of equine periocular squamous cell carcinoma (PSCC) was therefore conducted. We hypothesized that surgical excision with adjunctive local PDT is an effective and safe treatment for equine PSCC. Methods: Nine horses (10 eyes) with PSCC were treated with surgical resection, local infiltration of resulting wound beds with 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH) and irradiation with 665-nm wavelength ...
An overview of recent developments in corneal immunobiology: potential relevance in the etiogenesis of corneal disease in the horse. This paper overviews some recent developments in mammalian corneal immunobiology, and discusses how these may act as pointers towards understanding the immunology underlying some common corneal diseases in the horse, including infectious ulceration and presumptively immune-mediated non-ulcerative disease. Specifically, three aspects of corneal immunobiology are examined: the role of Toll-like receptors in surface immunity and in the etiogenesis of microbial ulceration, the relationship between conjunctiva associated lymphoid tissue (CALT) and immunoprotection of the corneal surface, and the me...
Epibulbar melanoma in a foal. A case of epibulbar melanoma in a 6-month-old, gelded, chestnut Hanoverian foal is reported. The location and clinical appearance upon initial presentation led to the tentative diagnosis of staphyloma or a congenital mass of unknown origin. An attempt was made to surgically excise the mass under general anesthesia, but due to its infiltrative nature and intraoperative appearance, most, but not all was removed without compromising the integrity of the globe. Histopathological evaluation revealed a multinodular to packeted, poorly demarcated, unencapsulated, infiltrative exophytic melanocytic ne...
Daily rhythm of tear production in normal horse. This study was designed to assess the daily rhythm of tear production in clinically healthy horses, to compare left eye and right eye, and to evaluate the influence of time and gender. Methods: For our study 18 horses (nine female and nine male) were subjected to three different light/dark (L/D) schedules: 12/12 L/D cycles, constant light (24/0 L/D) and constant darkness (0/24 L/D). Methods: In all subjects Schirmer tear tests were performed at 4-h intervals over a 24-h period. Results: A circadian rhythm of tear production was found during the 12/12 L/D period and during constant darkness. Al...
Deep lamellar endothelial keratoplasty in 10 horses. To describe and evaluate a surgical technique utilized for the therapy of deep corneal stromal abscesses (DSA) in horses. The DSA is excised and replaced with a partial thickness corneal lamellar allograft. Methods: A retrospective clinical study describing the indications for the surgical technique utilized and the outcomes of this procedure in 10 eyes of 10 horses. Results: Each affected eye had a discrete DSA within the posterior stroma. An initial partial thickness semicircular corneal incision was made at the limbus, followed by anterior stromal lamellar dissection over the lesion. After ...
Fluorangiographic study of the ocular fundus in normal horses. To describe the protocol and appearance of fluorescein angiography (FA) in normal horses. Methods: A total of 25 healthy horses aged between 5 and 15 years. Methods: The horses were sedated with 15 microg/kg detomidine and 50 microg/kg butorphanol and dilated with topical tropicamide 1%. All angiograms were recorded after intravenous bolus injection of 10 mg/kg of fluorescein sodium solution. Results: Two successive angiographic phases could be discerned: the choriopapillary phase, starting at 46.95 +/- 9.48 s, and the retinal vascular phase, starting at 47.79 +/- 10.38 s. The retinal vascular...
Update on veterinary cataract surgery. The purpose of this review is not to specifically discuss the techniques of veterinary cataract surgery, but rather to emphasize some of the differences between the veterinary and human cataract patients, procedures and outcomes. Results: In general, veterinary cataract surgery has more similarities than differences when compared to its human counterpart. This is especially true when comparing pediatric cataract patients. Veterinary cataract surgery has changed dramatically in recent years with regards to surgical technique, ocular pharmacology, viscoelastic devices, phacoemulsification, and t...
Doxycycline levels in preocular tear film of horses following oral administration. To determine the concentration of doxycycline in preocular tear film following oral administration in horses as a possible therapeutic modality for infectious and keratomalacic equine keratitis. Methods: Eight broodmares without ocular disease from a Thoroughbred breeding facility were included in this study. Each mare received 20 mg/kg of doxycycline by mouth once daily in the morning for five consecutive days. Tears were collected 1 h after doxycycline administration starting on day one of administration and continuing for 10 consecutive days. Doxycycline levels in the tears were measured us...
Evaluation of duration of corneal anesthesia induced with ophthalmic 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in clinically normal horses. To measure duration of corneal anesthesia and time and degree of maximal anesthetic effect of 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in horses. Methods: 10 clinically normal adult horses. Methods: Baseline corneal touch threshold (CTT) was measured in millimeters for 1 randomly selected eye of each horse by use of the aesthesiometer by applying the filament to the cornea at maximum length (60 mm) and decreasing in 5-mm increments until a consistent blink response was elicited. Following baseline CTT measurement, 0.2 mL of 0.5% proparacaine hydrochloride was in...
Ocular toxicity and distribution of subconjunctival and intravitreal rapamycin in horses. 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...
Congenital ocular anomalies in purebred and crossbred Rocky and Kentucky Mountain horses in Canada. 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...
Exophthalmus secondary to a sinonasal cyst in a horse. A 13-year-old female Miniature Horse was evaluated for progressive unilateral exophthalmia of the left globe of 3 weeks' duration. Results: Results of a physical examination were unremarkable. Ophthalmic examination identified exophthalmus of the left globe with complete resistance to retropulsion and mild blepharoconjunctivitis. Computed tomography revealed a large, space-occupying mass within the left caudal maxillary and left conchofrontal sinuses. The mass extended into the left retrobulbar space and contacted the cribriform plate. Trephination yielded copious amounts of turbid yellow flui...
Diagnostic ophthalmology. Squamous cell carcinoma. The research article deals with a case study of an 18-year old male horse suffering from an enlarging mass on its right lower eyelid, which was examined and diagnosed at […]
Surgical management of a progressive iris melanocytoma in a Mustang. A 7-year-old gray Mustang gelding weighing 454 kg was presented for evaluation of a brown mass within the left eye (OS) of 1 year's duration with recent enlargement. Results: A nonpainful, 8 mm diameter, brown, vascularized mass was identified in the anterior chamber of the OS. Ocular B-scan ultrasound confirmed iris involvement and corneal endothelial contact. Histopathology confirmed the presumptive diagnosis of a uveal melanocytic neoplasm, and revealed 1-3 mitotic figures per high power (400x) field. Results: The mass was removed via sector iridectomy without complications, but without com...
Corneal transplantation for inflammatory keratopathies in the horse: visual outcome in 206 cases (1993-2007). To evaluate the visual outcome of three techniques of corneal transplantation surgery in treating severe inflammatory keratopathies in the horse. Methods: Retrospective medical records study. Methods: Medical records of 206 horses that received corneal transplantation surgery at the University of Florida Veterinary Medical Center from 1993 to 2007 were reviewed. Methods: Data collected from the medical records included signalment, types of ocular lesions, type of transplant surgery performed, length of follow-up, complications, and visual outcomes. Results: Full thickness penetrating keratopla...
In vitro efficacy of an ophthalmic drug combination against corneal pathogens of horses. To evaluate the in vitro efficacy of an ophthalmic drug combination against common corneal pathogens of horses. Methods: Representative isolates of 3 bacterial and 2 fungal corneal pathogens of horses. Methods: Pathogens were subjected to minimum inhibitory concentration (MIC) testing of a drug combination that consisted of equal volumes of natamycin 3.33%, tobramycin 0.3%, cefazolin 5.5%, and equine serum. Proteinase inhibitory activity of the drug combination was assessed by use of a fluorescence microplate assay with gelatin and collagen I as substrates. The MICs of the drug combination wer...
Multidisciplinary management of a complicated orbital injury inflicted by a horse. This case report describes an unusual and complicated orbital injury inflicted by a horse. Definitive management required multidisciplinary surgical collaboration to prevent significant ocular sequelae. The diagnostic role of good imaging and the potential use of bio-models are highlighted.
Solute transport in the deep and calcified zones of articular cartilage. (1) To establish whether the tidemark and calcified cartilage are permeable to low molecular weight solutes, thereby providing a potential pathway for nutrition of cells in the deep cartilage. (2) To investigate transport from the subchondral microcirculation into calcified cartilage in an intact perfused joint and the effects on transport of static loading. Methods: The permeability of the tidemark and calcified cartilage was investigated in plugs of cartilage and subchondral bone which formed the membrane of a diffusion cell. Transport from the subchondral microcirculation and the effects of...
Detection of Leptospira interrogans DNA and antigen in fixed equine eyes affected with end-stage equine recurrent uveitis. Equine recurrent uveitis (ERU) is the most frequent cause of blindness in horses worldwide. Leptospira has been implicated as an etiologic agent in some cases of ERU and has been detected in fresh ocular tissues of affected horses. The objective of this study was to determine the presence of Leptospira antigen and DNA in fixed equine ocular tissues affected with end-stage ERU. Sections of eyes from 30 horses were obtained. Controls included 1) 10 normal equine eyes and 2) 10 equine eyes with a nonrecurrent form of uveitis. The experimental group consisted of 10 eyes diagnosed with ERU based on...
Pharmacokinetics of topically applied ciprofloxacin in equine tears. To evaluate the pharmacokinetics of topically applied ciprofloxacin 0.3% ophthalmic solution in tears of healthy horses. Methods: Twenty healthy, adult, mixed-breed horses. Methods: Twenty study horses were confirmed free of ophthalmic disease by complete ophthalmic examination. Seventy microliters of 0.3% ciprofloxacin (Ciloxan) was placed in the ventral cul-de-sac of each eye using a microliter syringe and 19-g cannula. Population kinetics were carried out by sampling the tear film from the lower cul-de-sac of each eye with tear test strips at 5, 10, 15 and 30 min and 1, 2, 4 and 6 h post ad...
Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex. To determine the prevalence of congenital stationary night blindness (CSNB) in Appaloosa horses in western Canada, investigate the association with the leopard complex of white spotting patterns, and further characterize the clinical and electroretinographic aspects of CSNB in the Appaloosa. Methods: Three groups of 10 Appaloosas were studied based on coat patterns suggestive of LpLp, Lplp, and lplp genotype. Methods: Neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of corneal diameter, streak retinoscopy, scotopic and photopic full-field and flicker ER...
Retinal detachment in horses: 40 cases (1998-2005). To determine clinical features, ophthalmic examination findings, etiology, treatment, and outcome of horses diagnosed with retinal detachment (RD). Methods: Forty horses, presented to the North Carolina State University and The Ohio State University Veterinary Teaching Hospitals from 1998 to 2005 that were diagnosed with RD. PROCEDURE(S): Horses with documented RD, confirmed either on ophthalmic examination or by ultrasonography, and with a complete medical record were included. Information retrieved from the medical records included signalment, presenting complaint, duration of clinical signs...
Evaluation of the in vivo behaviour of gentamicin sulphate ocular mini-tablets in ponies. The in vivo behaviour of 5% gentamicin sulphate ocular mini-tablets (2-mm diameter, 6.525 mg weight) was compared with gentamicin eye drops in six ponies. Two mini-tablets were inserted on the bulbar conjunctiva of the right eye while a similar dose of gentamicin was administered via eye drops in the left eye. Irritation induced by the mini-tablets and the eye drops was evaluated using a visual analogue scale (0-10). Tears were sampled with ophthalmologic absorption triangles for 1 min for the determination of the concentration of gentamicin sulphate using a microbiological plate diffusion met...
Grid keratotomy as a treatment for superficial nonhealing corneal ulcers in 10 horses. To describe the clinical symptoms of 10 cases of superficial nonhealing corneal ulcers in horses and to evaluate the results of grid keratotomy in these patients. Methods: Retrospective study. Methods: Ten horses with superficial nonhealing corneal ulceration in one eye. Methods: The signalment, history and clinical symptoms are reported of 10 patients with superficial nonhealing corneal ulcers during the period from August 2003 to February 2005. Grid keratotomy was performed in all cases. In addition, the surgical procedure of grid keratotomy and response to therapy are described. Results: Ho...
Ophthalmic emergencies in horses. The emergency clinician is frequently in the position of receiving, evaluating, and initiating treatment on horses with ophthalmic emergencies or orbital trauma. In the best of circumstances, an ophthalmologist is available to guide initial therapy and ultimately assume responsibility for the management of the patient during the remainder of its hospitalization, but this is not always the case. The information presented here is meant to provide the emergency clinician with basic guidelines for the initial assessment and management of horses sustaining ocular injuries or presented with an ophth...