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Home / Equine Research Bank / J Anat / The fibrous tapetum of the horse eye.
Journal of anatomy2013; 223(5); 509-518; doi: 10.1111/joa.12100

The fibrous tapetum of the horse eye.

Abstract: The tapetum lucidum is a light-reflective tissue in the eyes of many animals. Many ungulates have a fibrous tapetum. The horse has one of the largest eyes of any living animal and also has excellent vision in low-light environments. This study aimed to clarify the macroscopic tapetal shape, relationship between the tapetal thickness and the degree of pigmentation of the retinal pigment epithelium (RPE), spatial relationship between the visual streak and the tapetum, and wavelength of the light reflected from the tapetum in the horse. Macroscopically, weak light revealed the tapetum as a horizontal band located dorsal to and away from the optic disc. The tapetum expanded dorsally as the illumination increased. The tapetal tissue consisted of lamellae of collagen fibrils running parallel to the retinal surface; these spread over almost the entire ocular fundus and were thicker in the horizontal band dorsal to the disc. Only the horizontal band of the tapetum was covered by unpigmented RPE, suggesting that this band reflects light and is responsible for mesopic and scotopic vision. The visual streak was located in the ventral part of the horizontal band, ventral to the thickest part of the tapetum. The wavelength of the light reflected from the horizontal band of the tapetum was estimated from the diameter and interfibrous distance of the collagen fibrils to be approximately 468 nm. Therefore, the light reflected from the tapetum should be more effectively absorbed by rods than by cones, and should not interfere with photopic vision.
© 2013 Anatomical Society.
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Publication Date: 2013-09-15 PubMed ID: 24102505PubMed Central: PMC4399361DOI: 10.1111/joa.12100Google 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.

The research article examines the structure, function, and significance of the tapetum lucidum in horses. The study focuses on the physical aspects of the tapetum and its relationship with the visual performance of horses in low-light conditions.

Overview of the Study

  • The research aimed to understand various aspects of the fibrous tapetum in horses which include its shape, relationship with the pigmentation of the retinal pigment epithelium (RPE), its spatial relationship with the visual streak, and the wavelength of light it reflects.
  • This study is critical in understanding the horses’ impressive vision in low-light environments credited to the large-size eyes and the tapetum lucidum, a unique tissue that reflects light within their eyes.

Findings of the Study

  • Macroscopically, the tapetum appeared as a horizontal band located dorsal to (above) and away from the optic disc – this became more noticeable under weak light.
  • The horizontal band of the tapetum expanded when the illumination increased. It consisted of layers of collagen fibrils running parallel and covering almost the entire ocular fundus (interior surface of the eye).
  • The thickness of the tapetum was more significant in the horizontal band dorsal to the optic disc. This finding implies that horses have a specialized area in their eyes optimized for reflecting light.
  • This area of the tapetum was covered by non-pigmented RPE, suggesting its critical role in reflecting light and facilitating mesopic (partial light) and scotopic (low light) vision.
  • The visual streak, an area associated with the highest visual acuity, was found to be located ventral to (below) the thickest part of the tapetum, in the ventral part of the horizontal band.
  • Scientists estimated the wavelength of light reflected from the tapetum to be around 468 nm based on the diameter and interfibrous distance of the collagen fibrils.
  • The reflected light should be more efficiently absorbed by rods, the photoreceptor cells for low light conditions, than cones, and hence should not interfere with photopic (daylight) vision.

Significance of the Findings

  • this research provides crucial insights about the exceptional vision of horses, particularly in low-light conditions.
  • The study indicates that the unique structure and function of the tapetum in horses could be a biological adaptation to facilitate vision in minimal light.
  • Understanding the tapetum’s role can also aid in diagnosing and treating vision problems in horses.

Cite This Article

APA
Shinozaki A, Takagi S, Hosaka YZ, Uehara M. (2013). The fibrous tapetum of the horse eye. J Anat, 223(5), 509-518. https://doi.org/10.1111/joa.12100

Publication

Journal of anatomy
ISSN: 1469-7580
NlmUniqueID: 0137162
Country: England
Language: English
Volume: 223
Issue: 5
Pages: 509-518

Researcher Affiliations

Shinozaki, Aya
  • Department of Veterinary Medicine, Tottori University, Tottori, Japan.
Takagi, Satoshi
    Hosaka, Yoshinao Z
      Uehara, Masato

        MeSH Terms

        • Animals
        • Collagen / analysis
        • Eye / anatomy & histology
        • Horses / anatomy & histology
        • Pigmentation
        • Retinal Pigment Epithelium / anatomy & histology
        • Retinal Pigment Epithelium / ultrastructure

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        Citations

        This article has been cited 3 times.
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        2. Kotb AM, Ibrahim IA, Aly KH, Zayed AE. Histomorphometric analysis of the choroid of donkeys, buffalos, camels and dogs.. Int Ophthalmol 2019 Jun;39(6):1239-1247.
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