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.
Congenital ocular abnormalities of Rocky Mountain Horses. OBJECTIVE: To determine the incidence and describe ocular abnormalities in a cross-section of the population of Rocky Mountain Horses. Design: Prospective study. Animals: Five-hundred and fourteen Rocky Mountain Horses. Procedure: Ophthalmic examinations were performed using a slit-lamp biomicroscope and an indirect ophthalmoscope. Intraocular pressures were measured by applanation tonometry. Eyes from six horses were obtained for histologic examination. RESULTS: Cysts of the posterior iris, ciliary body, and peripheral retina were detected most frequently (249 horses), and were always located...
Systemic effects of topical and subconjunctival ophthalmic atropine in the horse. OBJECTIVE: To identify any systemic effects of topical and subconjunctival administration of atropine sulfate in the horse. Animals studied Six mature grade horses were treated hourly in one eye with topical ophthalmic atropine drops for 24 h. Five horses were treated subconjunctivally in one eye with 3 mg of atropine sulfate. Procedures Pupillary light reflexes, pupil size, electrocardiographic parameters, girth measurements, intestinal motility, and clinical signs of abdominal pain were monitored. RESULTS: Alteration in auscultated gut motility and clinical signs of abdominal pain were the m...
Tear-deficient and evaporative dry eye syndromes of the horse. Tear-deficient dry eye (keratoconjunctivitis sicca), and evaporative dry eye, with some overlap between these two categories, are two major categories of dry eye recognized in the horse. Careful examination of the eyelid margins, the inner and outer surfaces of the upper and lower eyelids, assessment of blink and third eyelid movement, specific testing of tear production, assessment of corneal sensitivity, and slit-lamp examination of the ocular surface before and after fluorescein dye application is recommended to detect dry eye problems. Rose Bengal dye application is also recommended in man...
Ulcerative keratitis caused by beta-hemolytic Streptococcus equi in 11 horses. Purpose To describe 11 clinical cases of ulcerative keratitis in horses associated with beta-hemolytic Streptococcus equi in Florida, USA. METHODS: Retrospective clinical study (1996-99). RESULTS: Beta-hemolytic Streptococcus equi was cultured from 11 horses with deep ulcers, descemetoceles or iris prolapse (n = 8), a suture abscess found with a penetrating keratoplasty for a stromal abscess (n = 1), and ulceration that developed following keratectomy/irradiation for corneal squamous cell carcinoma (n = 2). Beta-hemolytic Streptococcus equi subspecies zooepidemicus was found in 10 eyes and sub...
Treatment of equine glaucoma by transscleral neodymium:yttrium aluminum garnet laser cyclophotocoagulation: a retrospective study of 23 eyes of 16 horses. Contact neodymium:yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation (TSCP) was performed on 23 eyes of 16 horses for treatment of glaucoma. The mean highest preoperative IOP was 51 +/- 17 mmHg. Follow-up evaluation was available for 19 eyes 1 day after surgery, 14 eyes from 1 to 2 weeks, 16 eyes from 4 to 6 weeks, 9 eyes from 12 to 16 weeks, and 10 eyes greater than 20 weeks after laser treatment. The mean intraocular pressure (IOP) the day following surgery was 34 +/- 13 mmHg. The mean IOP for each follow-up period was: one to two weeks postoperative, 23 +/- 9 mmHg; fo...
Inferomedial placement of a single-entry subpalpebral lavage tube for treatment of equine eye disease. The objective of this study was to describe method of placement, and frequency and severity of complications associated with a subpalpebral lavage system placed in the medial aspect of the equine inferior eyelid. The inferomedial subpalpebral lavage (ISPL) tube is positioned deep in the medial aspect of the inferior conjunctival fornix so that the footplate lies flat between the lower eyelid and the anterior surface of the nictitans. Retrospective data from the placement of 92 ISPL systems placed in 86 horses during a 31-month period were examined. Tube placement was performed using sedation a...
Surgical management of equine recurrent uveitis with single port pars plana vitrectomy. Current information suggests that equine recurrent uveitis (ERU) is an immune-mediated reaction to infectious agents or to autologous ophthalmic tissue. Recurrences are associated with progression of irreversible ocular damage. This report describes the intraoperative technique, complications, and long-term results of 38 eyes in 35 horses with ERU that underwent pars plana vitrectomy. The majority of the horses were warm-blooded. Recurrence of ERU was prevented in 35 of the 38 eyes. Some horses, especially in patients with incipient cataracts, developed vision loss in postoperative, quiescent ...
Effect of single- and multiple-dose 0.5% timolol maleate on intraocular pressure and pupil size in female horses. OBJECTIVE: To determine the effect of single and multiple-dose 0.5% timolol maleate on intraocular pressure (IOP) and pupil size between 8 AM and 8 PM. Animals Nine female horses with normotensive eyes. Procedure IOP, horizontal and vertical pupil size were measured on a single day, between 8 AM and 8 PM at hours 0, 0.5, 1, 2, 4, 6, 8, 10, and 12. A single dose of 0.5% timolol maleate was applied to both eyes immediately after the first measurement at 8 AM. IOP and pupil size were measured at 8 AM and 4 PM in a 5-day experiment of twice-daily application of 0.5% timolol maleate. RESULTS: A sig...
Cochet-Bonnet aesthesiometer-determined corneal sensitivity in neonatal foals and adult horses. Corneal touch threshold (CTT) was measured in sick neonatal foals, healthy foals, and healthy adult horses with a Cochet-Bonnet aesthesiometer. The mean overall CTT for the adult horses, sick foals, and healthy foals was 4.82 +/- 0.87 cm, 3.21 +/- 0.24 cm, and 5.01 +/- 0.61 cm, respectively. The central cornea of adult horses was more sensitive than the limbal cornea. Corneal sensitivity was significantly reduced in sick neonatal foals compared to adults. The mean Schirmer I tear test values were significantly lower in foals than adults, and were 14.2 +/- 1.0 mm, 12.8 +/- 2.4 mm, and 18.3 +/- ...
Cataract phacofragmentation in horses. Cataract surgeries were carried out in fifty-one eyes of 36 horses over a 15-year period. Cataracts were removed using phacofragmentation and aspiration. Useful vision was restored after surgery in 30 horses. One year after surgery 16 of the 19 horses for which follow up information was available were still visual with several still being used as working horses. At 5-6 years after surgery three horses were still visual. The most frequent intraoperative complication was tearing of the posterior lens capsule. The most frequent postoperative problem was superficial corneal ulceration. Four eyes i...
Disease of the equine posterior segment. The appearance of the equine fundus is reviewed from the perspective of differentiating normal variations from disease, and the descriptions have been updated to include recently published ocular fundic abnormalities. Most pathological lesions are identified near the optic nerve head, and typically involve depigmentation or hyperpigmentation. Depending upon configuration and appearance, linear pigmented bands may reflect the course of the vortex veins, the transition from tapetal to nontapetal fundus, or indicate chorioretinitis or equine motor neuron disease. Choroidal vasculature is readily ...
Effect of topical administration of 2% dorzlamide hydrochloride or 2% dorzlamide hydrochloride-0.5% timolol maleate on intraocular pressure in clinically normal horses. To evaluate the effect of topical administration of 2% dorzolamide hydrochloride or 2% dorzolamide hydrochloride-0.5% timolol maleate on intraocular pressure (IOP) in clinically normal horses. Methods: 18 healthy adult horses without ocular abnormalities. Methods: The IOP was measured at 5 time points (7 AM, 9 AM, 11 AM, 3 PM, 7 PM) over 11 days. On days 1 and 2, baseline values were established. On days 3 through 5, horses received 2% dorzolamide HCI (group D, n = 9) or 2% dorzolamide HCl-0.5% timolol maleate (group DT, 9) in 1 randomly assigned eye every 24 hours immediately following each d...
Complications associated with anaesthesia for ocular surgery: a retrospective study 1989-1996. This retrospective study was initiated to identify complications of anaesthesia occurring during ocular surgery. Records of 74 horses anaesthetised for eye enucleation, 65 horses anaesthetised for surgery of the eye and adnexa, and 51 horses anaesthetised for splint bone excision were reviewed. Fifty-three percent of the horses anaesthetised for eye enucleation moved during surgery which was significantly more frequent than in the other groups (P = 0.001). The incidence of moving was significantly reduced by use of an anaesthetic gas analyser for monitoring (P = 0.001). Transient hypertension ...
Effect of an intravitreal cyclosporine implant on experimental uveitis in horses. The purpose of this study was to determine the effects of an intravitreal device releasing cyclosporine A (CsA) on recurrent inflammatory episodes in experimental uveitis. Nine normal horses were immunized peripherally with H37RA-mTB antigen twice, and then received 25 microg of H37RA-mTB antigen intravitreally in the right eye and an equal volume of balanced salt solution intravitreally in the left eye. Two weeks later, the animals randomly received either a CsA or a polymer implant (without CsA) in both eyes 1 week following implantation of the devices, 25 microg of H37RA-mTB antigen was rei...
Equine glaucoma: a retrospective study of 13 cases presented at the Western College of Veterinary Medicine from 1992 to 1999. The prevalence of equine glaucoma seen by the ophthalmology service at the Western College of Veterinary Medicine (WCVM) was 6.5%. The majority of cases (11/13) were associated with clinical manifestations of uveitis. Congenital glaucoma was documented in 1 case, and primary glaucoma was diagnosed in a 12-year-old quarter horse. There were no breed or sex predilections evident. Affected horses were middle-aged to old (average age = 9.5 years, ranging from 2 weeks to 23 years). The clinical manifestations of equine glaucoma included blindness, diffuse corneal edema, corneal vascularization, bup...
Corneal thickness, intraocular pressure, and optical corneal diameter in Rocky Mountain Horses with cornea globosa or clinically normal corneas. To compare corneal thickness, intraocular pressure, and optical corneal diameter in Rocky Mountain Horses with cornea globosa and those with clinically normal corneas. Methods: 129 Rocky Mountain Horses. Methods: Ultrasonic pachymetry was used to measure corneal thickness. Applanation tonometry was used to measure intraocular pressure. A Jameson caliper was used to measure optical corneal diameter. Results: The central and temporal peripheral portions of the cornea were significantly thicker in horses with cornea globosa than in horses with clinically normal corneas, but corneal thicknesses in...
The horse homolog of congenital aniridia conforms to codominant inheritance. Anterior segment dysgenesis syndrome occurs frequently in Rocky Mountain horses and has two distinct ocular phenotypes: (1) large cysts originating from the temporal ciliary body or peripheral retina and (2) multiple anterior segment anomalies including ciliary cysts, iris hypoplasia, iridocorneal adhesions and opacification, nuclear cataract, and megalocornea. To determine if anterior segment dysgenesis syndrome is heritable in horses we performed ophthalmic examinations and collected pedigree information on horses (n = 516) in an extended Rocky Mountain horse pedigree. Logistic regressive se...
Occurrence of Thelazia lacrymalis (Nematoda, Spirurida, Thelaziidae) in native horses in Abruzzo region (central eastern Italy). A survey on the prevalence of Thelazia spp. in Abruzzo region (Italy) in slaughtered native horses was conducted from August 29, 1997 to August 28, 1998. Both eyes from 128 eight-month to 11 year-old native animals were examined. 50 horses (39.06%) were found parasitized by Thelazia lacrymalis. 502 specimens (371 females, 88 males and 12 larvae) were collected. In the infected horses the numbers of T. lacrymalis ranged from 1 to 48, with a mean count burden of 3.92 per head (SD = 7.79). T. lacrymalis specimens were mainly in the excretory ducts of the Harderian gland, and also in the ducts of ...
Survey of retinal haemorrhages in neonatal thoroughbred foals. Twenty-seven of 167 neonatal thoroughbred foals (16 per cent) were found to have retinal haemorrhages after a careful examination of the entire fundus. Experience in differentiating haemorrhages from other lesions, and the selection of foals from normal populations, were considered to have an important effect on their apparent incidence. Bilateral haemorrhages were more common and there was a significantly higher incidence in female foals. The numbers of haemorrhages ranged between one and 20; 36 per cent of eyes with retinal haemorrhages had the small punctate type and 56 per cent had the spl...
The effect of supramaximal exercise on equine platelet function. When blood is collected into sodium citrate in the proportion of 9 parts blood:1 part sodium citrate, the concentration of plasma sodium citrate in the sample will depend on the packed cell volume (PCV) of the blood sample. This difference in plasma sodium citrate concentration secondary to alterations in PCV significantly affects human platelet aggregation responses. Since horses attain a high PCV in response to high-intensity exercise we investigated the effect of differences in sample plasma sodium citrate concentration on equine platelet aggregability. In addition, low molecular weight hep...
Diagnostic ophthalmology. Corneal ulcer with severe secondary anterior uveitis in a pony. The study reports on the diagnosis and treatment of a severe case of corneal ulceration and anterior uveitis in a 1-year-old Norwegian fjord pony, which did not respond to initial […]
[35 leptospira isolated from the vitreous body of 32 horses with recurrent uveitis (ERU)]. 130 vitreous samples, systematically collected in 1998 from 117 horses during vitrectomy, were cultured for the presence of leptospires. All horses suffered from equine recurrent uveitis (ERU), also known as periodic ophthalmia or moon blindness, and were treated surgically to combat painful attacks, and to preserve vision. In 35 out of 130 vitreous samples (35/130 = 26.9%), leptospires could be isolated. These isolates belong to the grippotyphosa serogroup (n = 31) and to the australis serogroup (n = 4). So, for the first time, leptospires were recovered from eyes in vivo in a large number of...
Equine infectious keratitis. Corneal ulcers are one of the most common ocular disease presentations in the horse. With the use of correct diagnostic techniques and selection of an appropriate treatment regimen, most cases result in a satisfactory outcome. The eye does not respond well to inflammation, and in complicated ulcers, this should be managed aggressively using systemic NSAIDs with a high priority assigned to removing the infectious agent. Care needs to be taken to avoid topical or systemic corticosteroid use for the treatment of equine ocular disease, however, unless the clinician is completely sure that the corn...
Subconjunctivally implanted micro-osmotic pumps for continuous ocular treatment in horses. To evaluate the feasibility of using a subconjunctivally implanted micro-osmotic pump for continuous delivery of medication to the eyes of horses- during a 7-day period. Methods: 4 healthy adult horses. Methods: With horses restrained in a standing position, micro-osmotic pumps were implanted subconjunctivally in each eye for 7 days. The treatment eye received an atropine-loaded micro-osmotic pump (100 microl of 1.5% atropine), and the contralateral eye received a sterile saline-loaded pump (100 microl of 0.9% NaCl) as a control treatment. Pupil size was measured at 12-hour intervals until val...
Systemic dexamethasone concentration in horses after continued topical treatment with an ophthalmic preparation of dexamethasone. To determine concentrations of dexamethasone in serum and urine of horses treated repeatedly with a topically administered ophthalmic dexamethasone preparation. Methods: 4 clinically normal horses (2 mares, 2 geldings). Methods: 0.1% dexamethasone ophthalmic ointment was administered to the left eye of each horse every 5 to 9 hours for 8 consecutive days, yielding an estimated cumulative dexamethasone dose of 6.4 microg/kg of body weight. Serum and urine samples were obtained before the first dexamethasone treatment, on days 4 and 8 of treatment, and 24, 48, and 96 hours after cessation of tre...
Ocular manifestations of equine motor neuron disease. The characteristics of the ocular manifestations of equine motor neuron disease (EMND) are described. Forty-two horses with histories, clinical signs and necropsies compatible with EMND were the subjects of this study. Ophthalmoscopic lesions that varied in severity were found in 40 of 42 horses and appeared as a distinct pigmented reticulated pattern at the tapetal-nontapetal junction or throughout the fundus, depending upon severity. The pattern colours ranged from yellow brown to black. Areas of hyperreflectivity formed mosaic patterns in the tapetal fundus. ERG B-wave amplitudes were usual...