Anatomy - Comparison of the eye between animals

Comparison of the eye between animals

Visual fields

Figure 1: Visual field of a carnivore (cat) and a herbivore (horse). a: Frontal position of cat's eyes results in narrow monocular visual field and wide binocular visual field. b: Lateral position of horse's eyes results in wide monocular visual field and narrow binocular visual field.
Source: Sjaastad O.V., Sand O. and Hove K. (2010) Physiology of domestic animals, 2nd edn., Oslo: Scandinavian Veterinary Press.
  • Animals eyes protrude from skull more
  • Carnivores and primates
    • Forward facing eyes
    • Binocular visual field > monocular visual field
    • Depth perception (stereoscopic vision)
    • Concentration on near objects
  • Herbivores
    • Laterally positioned eyes
    • Binocular visual field < monocular visual field
    • Panoramic vision

Orbit

Figure 2: Skulls of a carnivore (dog) and a herbivore (sheep). a: open orbit in dog. b: closed orbit in sheep.
Source: Sjaastad O.V., Sand O. and Hove K. (2010) Physiology of domestic animals, 2nd edn., Oslo: Scandinavian Veterinary Press.


  • Carnivores: 
    • Open orbit
    • Lateral orbital ligament
  • Herbivores: 
    • Closed orbit
    • Lateral bony orbital margin 

Pupil shape
  • Round: birds, dog, pig
  • Vertical slit: cat
  • Horizontal slit: large herbivores
  • All circular when dilated  

Anterioposterior flattening of eyeball
  • Horses and cattle
  • Ramp retina
    • Little accomodation is required for focusing on close objects

Tapetum 
  • Nocturnal adaptation
    • Reflection of incident light increases stimulation of light-sensitive receptor cells in retina à aids vision in dark
  • Ungulate: tapetum fibrosum - dense connective tissue
  • Carnivores: tapetum cellulosum - reflective cells
  • Diurnal species: lack tapetum

Pecten 

Figure 3: Transverse section of Avian eye
Source: Proctor N.S. and Lynch P.J. (1993) Manual of ornithology: Avian structure and function, 1st edn., New Haven: Yale University Press.
  • Birds 
  • Projection of retina into posterior chamber
  • Highly vascular 
  • Supply nutrients to retina

References
  1. Dyce K.M., Sack W.O. and Wensing C.J.G. (2010) Textbook of veterinary anatomy, 4th edn., Missouri: Saunders Elsevier.
  2. Proctor N.S. and Lynch P.J. (1993) Manual of ornithology: Avian structure and function, 1st edn., New Haven: Yale University Press.
  3. Samuelson D.A. (2007) Textbook of veterinary histology, 1st edn., Missouri: Saunders Elsevier.
  4. Sjaastad O.V., Sand O. and Hove K. (2010) Physiology of domestic animals, 2nd edn., Oslo: Scandinavian Veterinary Press.