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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

        References

        This article includes 30 references
        1. Afzelius BA. Section staining for electron microscopy using tannic acid as a mordant: a simple method for visualization of glycogen and collagen.. Microsc Res Tech 1992 Mar 1;21(1):65-72.
          pubmed: 1375520doi: 10.1002/jemt.1070210110google scholar: lookup
        2. Bellairs R, Harkness ML, Harkness RD. The structure of the tapetum of the eye of the sheep.. Cell Tissue Res 1975;157(1):73-91.
          pubmed: 1122534doi: 10.1007/bf00223231google scholar: lookup
        3. Bortolami R, Callegari E, Lucchi ML. Ultrastructural observations on the tapetum lucidum fibrosum.. Anat Histol Embryol 1979 Mar;8(1):72-8.
          pubmed: 157086doi: 10.1111/j.1439-0264.1979.tb00680.xgoogle scholar: lookup
        4. Braekevelt CR. Fine structure of the bovine tapetum fibrosum.. Anat Histol Embryol 1986 Sep;15(3):215-22.
          pubmed: 2947518doi: 10.1111/j.1439-0264.1986.tb00713.xgoogle scholar: lookup
        5. Carroll J, Murphy CJ, Neitz M, Hoeve JN, Neitz J. Photopigment basis for dichromatic color vision in the horse.. J Vis 2001;1(2):80-7.
          pubmed: 12678603doi: 10.1167/1.2.2google scholar: lookup
        6. Cutler TJ, Brooks DE, Andrew SE, Denis HM, Biros DJ, Gelatt KN, Komaromy AM, Kallberg M. Disease of the equine posterior segment.. Vet Ophthalmol 2000;3(2-3):73-82.
          pubmed: 11397286doi: 10.1046/j.1463-5224.2000.00138.xgoogle scholar: lookup
        7. Evans KE, McGreevy PD. The distribution of ganglion cells in the equine retina and its relationship to skull morphology.. Anat Histol Embryol 2007 Apr;36(2):151-6.
          pubmed: 17371390doi: 10.1111/j.1439-0264.2006.00749.xgoogle scholar: lookup
        8. François J, Wouters L, Victoria-Troncoso V, de Rouck A, van Gerven A. Morphometric and electrophysiologic study of the photoreceptors in the horse.. Ophthalmologica 1980;181(6):340-9.
          pubmed: 7243191doi: 10.1159/000309074google scholar: lookup
        9. Guo X, Sugita S. Topography of ganglion cells in the retina of the horse.. J Vet Med Sci 2000 Nov;62(11):1145-50.
          pubmed: 11129856doi: 10.1292/jvms.62.1145google scholar: lookup
        10. Hanggi EB, Ingersoll JF. Stimulus discrimination by horses under scotopic conditions.. Behav Processes 2009 Sep;82(1):45-50.
          pubmed: 19389464doi: 10.1016/j.beproc.2009.04.009google scholar: lookup
        11. Harman AM, Moore S, Hoskins R, Keller P. Horse vision and an explanation for the visual behaviour originally explained by the 'ramp retina'.. Equine Vet J 1999 Sep;31(5):384-90.
          pubmed: 10505953doi: 10.1111/j.2042-3306.1999.tb03837.xgoogle scholar: lookup
        12. Hebel R. Distribution of retinal ganglion cells in five mammalian species (pig, sheep, ox, horse, dog).. Anat Embryol (Berl) 1976 Dec 22;150(1):45-51.
          pubmed: 1015629doi: 10.1007/bf00346285google scholar: lookup
        13. Knill LM, Eagleton RD, Harver E. Physical optics of the equine eye.. Am J Vet Res 1977 Jun;38(6):735-7.
          pubmed: 879572
        14. Land MF. The physics and biology of animal reflectors.. Prog Biophys Mol Biol 1972;24:75-106.
          pubmed: 4581858doi: 10.1016/0079-6107(72)90004-1google scholar: lookup
        15. Matthews AG, Crispin SM, Parker J. The equine fundus. II: Normal anatomical variants and colobomata.. Equine Vet J Suppl 1990 Sep;(10):50-4.
          pubmed: 9079118doi: 10.1111/j.2042-3306.1990.tb04712.xgoogle scholar: lookup
        16. Murphy J, Hall C, Arkins S. What horses and humans see: a comparative review.. Int J Zool 2009;2009:1–14.
        17. Ollivier FJ, Samuelson DA, Brooks DE, Lewis PA, Kallberg ME, Komáromy AM. Comparative morphology of the tapetum lucidum (among selected species).. Vet Ophthalmol 2004 Jan-Feb;7(1):11-22.
          pubmed: 14738502doi: 10.1111/j.1463-5224.2004.00318.xgoogle scholar: lookup
        18. Sandmann D, Boycott BB, Peichl L. Blue-cone horizontal cells in the retinae of horses and other equidae.. J Neurosci 1996 May 15;16(10):3381-96.
          pmc: PMC6579128pubmed: 8627374doi: 10.1523/jneurosci.16-10-03381.1996google scholar: lookup
        19. Schwab IR, Yuen CK, Buyukmihci NC, Blankenship TN, Fitzgerald PG. Evolution of the tapetum.. Trans Am Ophthalmol Soc 2002;100:187-99; discussion 199-200.
          pmc: PMC1358962pubmed: 12545693
        20. Seiferle E. Sinnesorgane. In: Nickel R, Schummer A, Seiferle E, editors. Lehrbuch der Anatomie der Haustiere, Band 4, Nervensystem, Sinnesorgane, Endokrine Drüsen. Berlin: Paul Parey; 1975. pp. 337–398.
        21. Shinozaki A, Hosaka Y, Imagawa T, Uehara M. Topography of ganglion cells and photoreceptors in the sheep retina.. J Comp Neurol 2010 Jun 15;518(12):2305-15.
          pubmed: 20437529doi: 10.1002/cne.22333google scholar: lookup
        22. Shinozaki A, Hosaka Y, Imagawa T, Uehara M. Relationship between distribution of tapetum fibrosum and retinal pigment epithelium in the sheep eye.. J Vet Med Sci 2010 Feb;72(2):211-5.
          pubmed: 19942810doi: 10.1292/jvms.09-0413google scholar: lookup
        23. Timney B, Keil K. Visual acuity in the horse.. Vision Res 1992 Dec;32(12):2289-93.
          pubmed: 1288005doi: 10.1016/0042-6989(92)90092-wgoogle scholar: lookup
        24. Timney B, Macuda T. Vision and hearing in horses.. J Am Vet Med Assoc 2001 May 15;218(10):1567-74.
          pubmed: 11393366doi: 10.2460/javma.2001.218.1567google scholar: lookup
        25. Walls GL. The Vertebrate Eye and Its Adaptive Radiation. New York: Hafner; 1967.
        26. Waring GH. Horse Behavior. 2nd edn. New York: Noyes Publications/William Andrew Publishing; 2003. Perception and orientation; pp. 18–35.
        27. Watanabe T, Hosaka Y, Yamamoto E, Ueda H, Sugawara K, Takahashi H, Takehana K. Control of the collagen fibril diameter in the equine superficial digital flexor tendon in horses by decorin.. J Vet Med Sci 2005 Sep;67(9):855-60.
          pubmed: 16210795doi: 10.1292/jvms.67.855google scholar: lookup
        28. Wouters L, De Moor A. Ultrastructure of the pigment epithelium and the photoreceptors in the retina of the horse.. Am J Vet Res 1979 Aug;40(8):1066-71.
          pubmed: 525910
        29. Young NM, Hope GM, Dawson WW. The tapetum fibrosum in the eyes of two small whales.. Mar Mamm Sci 1988;4:281–290.
        30. Zhao H, Ru B, Teeling EC, Faulkes CG, Zhang S, Rossiter SJ. Rhodopsin molecular evolution in mammals inhabiting low light environments.. PLoS One 2009 Dec 16;4(12):e8326.
          pmc: PMC2790605pubmed: 20016835doi: 10.1371/journal.pone.0008326google scholar: lookup

        Citations

        This article has been cited 5 times.
        1. Zueva L, Zayas-Santiago A, Rojas L, Sanabria P, Alves J, Tsytsarev V, Inyushin M. Multilayer subwavelength gratings or sandwiches with periodic structure shape light reflection in the tapetum lucidum of taxonomically diverse vertebrate animals. J Biophotonics 2022 Jun;15(6):e202200002.
          doi: 10.1002/jbio.202200002pubmed: 35243792google scholar: lookup
        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.
          doi: 10.1007/s10792-018-0932-0pubmed: 29721841google scholar: lookup
        3. Yamaue Y, Hosaka YZ, Uehara M. Spatial relationships among the cellular tapetum, visual streak and rod density in dogs. J Vet Med Sci 2015 Feb;77(2):175-9.
          doi: 10.1292/jvms.14-0447pubmed: 25728250google scholar: lookup
        4. Roth LSV, McGreevy P. Horse vision through two lenses: Tinbergen's Four Questions and the Five Domains. Front Vet Sci 2025;12:1647911.
          doi: 10.3389/fvets.2025.1647911pubmed: 40895790google scholar: lookup
        5. Cobo R, Navarro-Sempere A, Segovia Y, García M. Adaptations of the Vertebrate Retina to Low-Light Conditions: A Review. Anat Histol Embryol 2025 Jul;54(4):e70042.
          doi: 10.1111/ahe.70042pubmed: 40396371google scholar: lookup
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