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Veterinary ophthalmology2023; 26(4); 297-305; doi: 10.1111/vop.13061

Prevalence, differences, and potential correlation to age, sex, breed, coat color, iris color, and geographic location in naturally occurring refractive errors in the normal equine eye from Germany and North Carolina.

Abstract: To evaluate the normal refractive state in horses in NCSU and ECMR and determine the prevalence of naturally occurring refractive errors and their association with breed, age, coat color, iris color, sex, and geographic location. Methods: Horses from NCSU (January 2009-November 2012) and ECMR (January 2013-September 2016) underwent ophthalmic examination and streak retinoscopy. Location, color, breed, sex, and iris color were recorded. Gross and net refractive values for each meridian (horizontal and vertical), spherical refraction, astigmatism for both eyes, and anisometry were recorded, and statistical analyses were performed. Results: There is excellent agreement in refraction between the eyes of the same horse (ICC = 0.89). The median net horizontal (H), vertical (V), and spherical refraction for the total population (n = 690) were H: +0.25 D (min. -6.50 D, max. +2.34 D), V: +0.25 D (min. -7.13 D, max. +2.75D), and spherical: +0.25 D (min. -6.82 D, max. +2.17 D), all with interquartile ranges of -0.25 to 0.25 D. Emmetropia (>-0.50 D and -0.75 D and <+0.75 D) was present in 769/1380 eyes (55.7%) and 926/1380 eyes (67.1%), respectively. Anisometropia was present in 86/690 horses (12.5%). Sex, iris color, and location were significantly associated with refraction values, whereas age, breed, and coat color were not. Conclusions: Most eyes evaluated are emmetropic, or shifted myopically, with excellent agreement between eyes of the same horse. Sex, iris color, and geographic location appear to impact refraction in horses. Background: None.
© 2023 American College of Veterinary Ophthalmologists.
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Publication Date: 2023-01-24 PubMed ID: 36692054DOI: 10.1111/vop.13061Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research aims to assess the normal refractive state in horses and the prevalence of naturally occurring refractive errors. It also looks at whether these errors are linked to factors such as breed, age, coat color, iris color, sex, and geographic location. The research findings indicate that most horses have normal vision or a slight shift towards myopia and that sex, iris color, and geographic location can impact how light is bent within the horse’s eye.

Methods

  • The researchers conducted an ophthalmic examination on horses from North Carolina State University (NCSU) from 2009 to 2012 and the European College of Veterinary Ophthalmologists (ECMR) from 2013 to 2016.
  • The examination involved a streak retinoscopic procedure, a test that measures the way light is bent as it enters the eye.
  • Details such as the horse’s location, color, breed, sex, and iris color were recorded.
  • The refractive values in the horizontal and vertical directions, overall spherical refraction, astigmatism in both eyes, and anisometry (difference in refractive error between the eyes) were recorded.
  • The data was then statistically analysed to look for patterns or correlations.

Results

  • The results showed a high consistency in refraction between both eyes of the same horse and a tendency towards emmetropia (normal vision) or slight myopia (nearsightedness).
  • The median net horizontal, vertical, and spherical refraction measurements across the full population tested were found to be low, indicating most horses have normal vision. They also found a range of refraction from -6.50 to +2.34 D in the horizontal direction, -7.13 to +2.75D in the vertical direction, and -6.82 to +2.17 D in spherical refraction.
  • It was found that 55.7% and 67.1% of the total number of eyes examined were emmetropic under correspondingly changing thresholds of ±0.50D and ±0.75D, respectively.
  • Anisometropia, a condition where the two eyes have significantly differing refractive power, was present in 12.5% of the horses.
  • The horse’s sex, iris color, and geographic location were identified as having a significant association with refraction values. However, age, breed, and coat color did not have a significant correlation.

Conclusions

  • The majority of the horses evaluated were found to have normal vision or only a slight shift towards myopia.
  • The study concludes that the sex, iris color, and geographic location of a horse could affect its refractive state and these factors should be considered when diagnosing or treating vision problems in horses.
  • The study does not find statistically significant connections between a horse’s refractive state and factors such as age, breed, and coat color.

Cite This Article

APA
Charnock LN, Davidson MG, Keys DA, Gilger BC, McMullen RJ. (2023). Prevalence, differences, and potential correlation to age, sex, breed, coat color, iris color, and geographic location in naturally occurring refractive errors in the normal equine eye from Germany and North Carolina. Vet Ophthalmol, 26(4), 297-305. https://doi.org/10.1111/vop.13061

Publication

Veterinary ophthalmology
ISSN: 1463-5224
NlmUniqueID: 100887377
Country: England
Language: English
Volume: 26
Issue: 4
Pages: 297-305

Researcher Affiliations

Charnock, Lauren N
  • College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA.
Davidson, Michael G
  • North Carolina State University, Raleigh, North Carolina, USA.
Keys, Deborah A
  • Kaleidoscope Statistics, Athens, Georgia, USA.
Gilger, Brian C
  • North Carolina State University, Raleigh, North Carolina, USA.
McMullen, Richard J
  • College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA.
  • Equine Clinic Munich-Riem, Munich, Germany.

MeSH Terms

  • Horses
  • Animals
  • Prevalence
  • North Carolina
  • Refractive Errors / epidemiology
  • Refractive Errors / veterinary
  • Refraction, Ocular
  • Germany / epidemiology
  • Iris
  • Horse Diseases

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Citations

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