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[[Image:Eye_lizards.jpg|300px|thumb|right|'''Iguana eye (left), Tokay gecko eye (right)''' (Copyright © RVC and its licensors, Sean Bobbit, Sue Evans, Andrew Devare and Claire Moore. All rights reserved)]]
[[Image:Eye_lizards.jpg|300px|thumb|right|'''Iguana eye (left), Tokay gecko eye (right)''' (Copyright © RVC and its licensors, Sean Bobbit, Sue Evans, Andrew Devare and Claire Moore. All rights reserved)]]
[[Image:Lizard_skull_mandible.jpg|150px|thumb|right|'''Parietal eye on the dorsum of the head''' (Copyright © RVC and its licensors, Sean Bobbit, Sue Evans, Andrew Devare and Claire Moore. All rights reserved)]]
[[Image:Lizard_skull_mandible.jpg|150px|thumb|right|'''Parietal eye on the dorsum of the head''' (Copyright © RVC and its licensors, Sean Bobbit, Sue Evans, Andrew Devare and Claire Moore. All rights reserved)]]
[[Image:Panther_Chameleon.jpg|300px|thumb|right|'''Chameleon spectacle''' (Copyright © RVC and its licensors, Sean Bobbit, Sue Evans, Andrew Devare and Claire Moore. All rights reserved)]]
[[Image:Panther_Chameleon.jpg|300px|thumb|right|'''Chameleon spectacle''' (Wikimedia Commons)]]
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.