Raptor Ophthalmology: Anatomy of the Avian Eye

Key Points

  • The avian eye is both relatively and absolutely large relative to its body size.
  • The sclera is invested with a ring of small bones anteriorly and cartilage posteriorly.
  • All birds have some degree of striated muscle in their iris making the use of parasympatholytic agents (eg atropine) ineffective in bringing about dilation.
  • Birds lack a choroidal tapetum.
  • The avascular retina is nourished by the externally situated choroid and the internally projecting pecten. The pecten is a heavily pigmented, highly vascularized, pleated structure that projects into the vitreous from a base situated upon the optic nerve. The pecten limits visualization of the optic nerve to a thin rim a the base of the pecten.

A bird is a wing guided by an eye… Rochon-Duvigneaud: Lex Yeux et La Vision Des Vertebres

The avian eye is a large structure that takes up a significant portion of cranial mass. Raptors depend heavily on vision in order to compete successfully for survival. The posterior aspect of the eye fits snugly within the large bony orbit. The globes are separated by a thin interorbital septum, which measures significantly less than 1 mm in some areas . . .

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