Congenital ocular abnormalities of Rocky Mountain Horses.
Abstract: 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 temporally. Curvilinear streaks of retinal pigmented epithelium extending from the peripheral temporal retina marked the boundary of previous retinal detachment in 189 horses. Retinal dysplasia was detected in 125 horses. Multiple ocular anomalies were evident in 71 horses and were always bilateral and symmetrical. Affected eyes had a large, clear cornea that protruded excessively and had an apparent short radius of curvature, a deep anterior chamber, miotic and dyscoric pupil, and iris hypoplasia. Pupillary light responses were decreased or absent and pupils failed to dilate after repeated instillation of mydriatic drugs in horses with multiple ocular anomalies. Less frequently encountered abnormalities included peripheral iridocorneal adhesions and goniosynechiae. Congenital cataract was always present in eyes with multiple abnormalities. Intraocular pressures did not differ among horses with normal eyes and horses with multiple ocular abnormalities. Histologic examination of eyes corroborated the clinical appearance.
Publication Date: 2001-06-09 PubMed ID: 11397242DOI: 10.1046/j.1463-5224.1999.00050.xGoogle Scholar: Lookup
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- Journal Article
Summary
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This research aimed to determine and describe the occurrence and nature of eye abnormalities in a population of Rocky Mountain Horses. The study found that multiple eye anomalies, including retinal detachment and iris hypoplasia, were common in these horses, and noted the presence of congenital cataracts in eyes with multiple abnormalities.
Research Design and Procedure
- The researchers carried out a prospective study on a sample of 514 Rocky Mountain Horses.
- They performed ophthalmic examinations on these horses using tools like a slit-lamp biomicroscope and an indirect ophthalmoscope.
- Intraocular pressures were measured using an applanation tonometer. This approach relies on the ‘applanation’ or flattening of the cornea to establish the intraocular pressure.
- For histologic examination, the researchers collected eyes from six horses. Histology involves the study of the microscopic structure of tissues.
Key Findings
- The most common ocular abnormality found was temporal cysts in the iris, ciliary body, and peripheral retina, detected in 249 horses.
- In 189 horses, the researchers noted curvilinear streaks of retinal pigmented epithelium extended from the peripheral temporal retina, marking previous retinal detachment.
- Retinal dysplasia, or the abnormal development of the retina, was present in 125 horses.
- Multiple ocular anomalies were found in 71 horses, and these were always bilateral (affecting both eyes) and symmetrical.
Characteristics of Affected Eyes
- Affected eyes exhibited a large, excessively protruding clear cornea, a deep anterior chamber, a miotic (constricted) and dyscoric (irregularly shaped) pupil, and iris hypoplasia or underdevelopment.
- These eyes showed decreased or no pupillary light responses, and the pupils failed to dilate even after administering mydriatic drugs, which are typically used to enlarge the pupil.
- Congenital cataract was always found in eyes with multiple abnormalities.
- Notably, intraocular pressures did not vary between horses with normal eyes and those with multiple ocular abnormalities.
- The results of histologic examination affirmed the clinical observation of these abnormalities.
Cite This Article
APA
Ramsey DT, Ewart SL, Render JA, Cook CS, Latimer CA.
(2001).
Congenital ocular abnormalities of Rocky Mountain Horses.
Vet Ophthalmol, 2(1), 47-59.
https://doi.org/10.1046/j.1463-5224.1999.00050.x Publication
Researcher Affiliations
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314, USA; Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314, USA; Pathology and Animal Health Diagnostic Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314, USA; Veterinary Vision, 219 North Amphlett Blvd, San Mateo, CA 94401, USA; Rood & Riddle Equine Hospital, PO Box 12070, Lexington, KY 40513-1126, USA.
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