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==Introduction==
Common mydriatics have no effect on the reptilian eye because both the iris sphincter and ciliary muscle contain striated (or skeletal) rather than smooth muscle. This means that they are under conscious control. Therefore, unlike mammals, the consensual pupillary response is absent, the cornea does not contain a Descemets membrane and scleral ossicles are often present. This renders the ocular examination more challenging but more importantly, the parasympatholytic topical drugs (that reduce the activity of the parasympathetic nervous system) used to dilate the pupil (mydriasis) in mammals are totally ineffective.
Common mydriatics have no effect on the reptilian eye because both the iris sphincter and ciliary muscle contain striated (or skeletal) rather than smooth muscle. This means that they are under conscious control. Therefore, unlike mammals, the consensual pupillary response is absent, the cornea does not contain a Descemets membrane and scleral ossicles are often present. This renders the ocular examination more challenging but more importantly, the parasympatholytic topical drugs (that reduce the activity of the parasympathetic nervous system) used to dilate the pupil (mydriasis) in mammals are totally ineffective.
A well developed parietal eye (with a lens and retina) is found in some lizards including the Green iguana. It functions in hormone regulation.
A well developed parietal eye (with a lens and retina) is found in some lizards including the Green iguana. It functions in hormone regulation.
Another characteristic of the lizard eye is its ability to occupy both scotopic (light limited) and photopic (light rich) environments. Indeed, the morphology of the eye adapts and varies according to activity in these different light environments.
==Eyelids==
==Eyelids==
==References==
==References==
* Girling, S.J. (2004). ''BSAVA Manual of Reptiles''. British Small Animal Veterinary Association. pp. 350. ISBN 0905214757
* Hall, M.I. (2008). Comparative analysis of the size and shape of the lizard eye. Zoology 111, 62-75
* Mader, D.R. (2005). ''Reptile Medicine and Surgery''. Saunders. pp. 1264. ISBN 072169327X
* Mader, D.R. (2005). ''Reptile Medicine and Surgery''. Saunders. pp. 1264. ISBN 072169327X