Veterinary ophthalmology2011; 14(2); 100-108; doi: 10.1111/j.1463-5224.2010.00847.x

Ocular anomalies in a herd of Exmoor ponies in Canada.

Abstract: To characterize the ocular anomalies, determine their recurrence in families and assess the mode of inheritance of the most prevalent anomalies through pedigree analysis in a herd of Exmoor ponies. Methods: Thirty Exmoor ponies residing in south-western Ontario, Canada. Methods: Ophthalmic examination was performed using direct ophthalmoscopy, slit-lamp biomicroscopy and indirect ophthalmoscopy, pre- and post-pupillary dilation. Following compilation of ocular findings, pedigree analysis was conducted to assess the recurrence pattern of specific anomalies in families and the data were tested for significance for breed prevalence and gender dependence, using Fisher's exact test. Results: Twenty-eight purebred ponies and two cross-breds, ranging from 14 days to 31 years were examined. A prominent brow above the eyes characteristic of this breed was a consistent periocular feature of adult ponies. In nine ponies, eyelid sarcoid, iris nevus, Mittendorf's dot, hyaloid artery remnant, and hyper-reflective vitreal strands were detected while the lesions recorded in the remaining 21 included macroblepharon, persistent pupillary membranes, iris hypoplasia, cataracts, focal choroidal or retinal pigment epithelium hypoplasia and optic nerve head coloboma. The most common ocular finding was cataracts seen mainly in females. Statistical tests on prevalence data confirmed a significant breed and sex association. Pedigree analysis favored a sex-linked mode of inheritance for cataracts in this line of Exmoor ponies. Conclusions: Although the ocular anomalies detected in this group have been previously reported in other breeds of horses, this is the first report of equine cataracts showing a familial trend suggestive of a sex-linked genetic defect.
Publication Date: 2011-03-04 PubMed ID: 21366825DOI: 10.1111/j.1463-5224.2010.00847.xGoogle Scholar: Lookup
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The research article investigates various eye abnormalities in a Canadian herd of Exmoor ponies, their genetic transmission, and the most common abnormalities’ mode of inheritance through pedigree analysis. The study reveals that cataracts were the most prevalent ocular anomaly, predominantly in female ponies, suggesting a sex-linked genetic defect.


  • The study was carried out on a group of thirty Exmoor ponies situated in south-western Ontario, Canada. The selected ponies varied in age, from 14 days old to 31 years old. The group comprised of twenty-eight purebred and two crossbred ponies.
  • Ophthalmic examinations involved direct ophthalmoscopy, slit-lamp biomicroscopy, and indirect ophthalmoscopy, conducted both pre- and post-pupillary dilation. These tests were used to identify and record ocular anomalies in the ponies.
  • Once the ocular findings were compiled, pedigree analysis was performed to investigate the recurrence of specific anomalies in the related families. Then, this data was statistically analyzed for breed prevalence and gender dependence using Fisher’s exact test.


  • The researchers discovered that adult ponies exhibited a consistently prominent brow above their eyes, a distinctive characteristic of the breed.
  • Several ocular anomalies were detected in the ponies. Nine ponies showed signs of eyelid sarcoid, iris nevus, Mittendorf’s dot, hyaloid artery remnant, and hyper-reflective vitreal strands. The other 21 ponies presented with macroblepharon, persistent pupillary membranes, iris hypoplasia, cataracts, focal choroidal or retinal pigment epithelium hypoplasia, and optic nerve head coloboma.
  • Out of all the observed anomalies, cataracts were the most frequent, particularly in female ponies.
  • A statistically significant association between the breed and gender with the prevalence of these anomalies was confirmed. The results favored a sex-linked mode of inheritance for cataracts specifically.


  • While the ocular anomalies identified in the research study have been previously recorded in other horse breeds, this study is the first to report a familial pattern suggestive of a sex-linked genetic defect causing equine cataracts.
  • The finding highlights the potential importance of genetics in the transmission and occurrence of ocular anomalies in different horse breeds, shedding new light on equine ocular health.

Cite This Article

Pinard CL, Basrur PK. (2011). Ocular anomalies in a herd of Exmoor ponies in Canada. Vet Ophthalmol, 14(2), 100-108.


ISSN: 1463-5224
NlmUniqueID: 100887377
Country: England
Language: English
Volume: 14
Issue: 2
Pages: 100-108

Researcher Affiliations

Pinard, Chantale L
  • Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.
Basrur, Pari K

    MeSH Terms

    • Animals
    • Canada
    • Eye Diseases / genetics
    • Eye Diseases / pathology
    • Eye Diseases / veterinary
    • Female
    • Genetic Predisposition to Disease
    • Horse Diseases / genetics
    • Horse Diseases / pathology
    • Horses
    • Male
    • Pedigree


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