Refractive state of the Spanish Thoroughbred horse: a comparison with the Crossbred horse.
Abstract: To assess the refractive state of the equine eye utilizing retinoscopy. To compare the refractive state of Spanish Thoroughbred horses with the refractive state of Crossbred horses. Methods: The refractive state of 135 horses (264 eyes) was assessed utilizing streak retinoscopy. Two perpendicular meridians were examined in order to assess astigmatism at a working distance of approximately 67 cm. A group of 81 Spanish Thoroughbred horses was compared with a group of 54 Crossbred horses. Cyclopentolate ophthalmic solution was instilled in the eyes of a group of 18 horses to determine if accommodation has any influence on the assessment of the refractive state. Results: Mean ± SE refractive state of all horses examined was -0.17 ± 0.04 D. The mean refractive state of the Spanish Thoroughbred was -0.28 ± 0.06 D while that of the Crossbred was -0.01 ± 0.05 D. The refractive state of the Spanish Thoroughbred was found to be statistically different to that of the Crossbred. The most prevalent refractive state was emmetropia in all cases, followed by hyperopia for the Crossbred, and myopia for the Spanish Thoroughbred. Astigmatism ≥0.50 D present in both eyes from the same individual was found in 21.7% of all horses examined. Anisometropia ≥1.00 D was diagnosed in 4 out of 129 horses with both visual eyes. Cycloplegia did not statistically affect the refractive state of the evaluated eyes. Conclusions: The equine eye has a refractive state close to emmetropia. Myopia is higher among Spanish Thoroughbred horses than among Crossbred horses.
© 2012 American College of Veterinary Ophthalmologists.
Publication Date: 2012-04-09 PubMed ID: 22487240DOI: 10.1111/j.1463-5224.2012.01014.xGoogle Scholar: Lookup
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- Comparative Study
- Journal Article
- Breed Differences
- Clinical Examination
- Clinical Findings
- Clinical Pathology
- Clinical Study
- Comparative Study
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Equine Diseases
- Equine Health
- Equine Research
- Eyes
- Horses
- Ophthalmology
- Species Comparison
- Thoroughbreds
- Veterinary Care
- Veterinary Medicine
- Veterinary Practice
- Veterinary Research
Summary
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The research studies the refractive state of the eyes in both Spanish Thoroughbred and Crossbred horses, using retinoscopy. The results show that although most horses have a refractive state close to emmetropia, the Spanish Thoroughbred tend to be more myopic than the Crossbred horses.
Experiment Methods
- The study analyzed the refractive state of 135 horses (264 eyes) using streak retinoscopy. This method of evaluating the refractive state of the eye involves shining a light into the eye and observing the reflection off the retina.
- In each horse, two perpendicular meridians were examined to evaluate the level of astigmatism. The test was performed at a working distance of about 67 cm.
- The sample size consisted of 81 Spanish Thoroughbred horses and 54 Crossbred horses whose refractive states were compared.
- To determine the influence of accommodation on the refractive state, a Cyclopentolate ophthalmic solution was instilled in the eyes of 18 horses.
Results of the Research
- The average refractive state for all horses examined was -0.17 ± 0.04 D.
- The average refractive state of the Spanish Thoroughbred was -0.28 ± 0.06 D, while that of the Crossbred was -0.01 ± 0.05 D. Thus, demonstrating a significantly different refractive state between the two horse breeds.
- Emmetropia, a condition where the eye is at rest and the image is focused exactly on the retina, was the most prevalent refractive state in all the horses tested. This was followed by hyperopia in the Crossbred horses and myopia in the Spanish Thoroughbred horses.
- Astigmatism, a defect in the eye or in a lens caused by a deviation from spherical curvature, measuring at or above 0.50 D in both eyes from the same horse, was observed in 21.7% of all the horses tested.
- Anisometropia, a condition where the two eyes have unequal refractive power, at or above 1.00 D was found in 4 out of the 129 horses with both eyes usable for vision.
- Administration of Cycloplegia, a solution used to dilate the pupil and paralyze accommodation, was found not to significantly affect the refractive state of the evaluated eyes.
Conclusion From the Study
- The equine eye’s refractive state is typically close to emmetropia, indicating a predominance of normal refractive status.
- Between the two horse breeds, a higher prevalence of myopia was observed among the Spanish Thoroughbred horses as compared to the Crossbred horses.
Cite This Article
APA
Rull-Cotrina J, Molleda JM, Gallardo J, Martín-Suárez E.
(2012).
Refractive state of the Spanish Thoroughbred horse: a comparison with the Crossbred horse.
Vet Ophthalmol, 16(1), 25-28.
https://doi.org/10.1111/j.1463-5224.2012.01014.x Publication
Researcher Affiliations
- Department of Animal Medicine and Surgery, University of Cordoba, Campus de Rabanales, Ctra Madrid-Cádiz km 396, 14071 Córdoba, Spain. opticaveterinaria@gmail.com
MeSH Terms
- Animals
- Astigmatism / diagnosis
- Astigmatism / veterinary
- Emmetropia
- Female
- Horse Diseases / diagnosis
- Horses / physiology
- Male
- Myopia / diagnosis
- Myopia / veterinary
- Refraction, Ocular / physiology
- Retinoscopy / veterinary
- Species Specificity
Citations
This article has been cited 4 times.- Ross M, Ofri R, Aizenberg I, Abu-Siam M, Pe'er O, Arad D, Rosov A, Gootwine E, Dvir H, Honig H, Obolensky A, Averbukh E, Banin E, Gantz L. Naturally-occurring myopia and loss of cone function in a sheep model of achromatopsia. Sci Rep 2020 Nov 9;10(1):19314.
- Bueno JM, Lo Sapio M, Sanes JM, Seva J. Analysis of the Ocular Refractive State in Fighting Bulls: Astigmatism Prevalence. Biomed Res Int 2017;2017:8203269.
- Johansson MK, Jäderkvist Fegraeus K, Lindgren G, Ekesten B. The refractive state of the eye in Icelandic horses with the Silver mutation. BMC Vet Res 2017 Jun 2;13(1):153.
- Roth LSV, McGreevy P. Horse vision through two lenses: Tinbergen's Four Questions and the Five Domains. Front Vet Sci 2025;12:1647911.
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