Journal of comparative physiology

, Volume 125, Issue 4, pp 335–339

The refractive significance of the nictitating membrane of the bird eye

Authors

  • J. G. Sivak
    • Laboratory of Comparative OptometryUniversity of Waterloo
  • W. R. Bobier
    • Laboratory of Comparative OptometryUniversity of Waterloo
  • B. Levy
    • Laboratory of Comparative OptometryUniversity of Waterloo
Article

DOI: 10.1007/BF00656868

Cite this article as:
Sivak, J.G., Bobier, W.R. & Levy, B. J. Comp. Physiol. (1978) 125: 335. doi:10.1007/BF00656868

Summary

Previous authors have suggested that in certain aquatic birds a transparent nictitating membrane of high refractive index could compensate for the refractive loss of the cornea in water. Measurements of refractive indices, refractive state and curvature carried out on a number of aquatic birds indicate that the nictitating membrane does not have a refractive function; the refractive indices of the cornea and nictitating membrane are very similar (approximately 1.37), the nictitating membrane does not alter the refractive state of the eye, and its curvature, when it is in place in front of the globe, is virtually the same as that of the cornea.

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Copyright information

© Springer-Verlag 1978