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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:Panther_Chameleon.jpg|300px|thumb|right|'''Chameleon eye''' (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 eye''' (Copyright © RVC and its licensors, Sean Bobbit, Sue Evans, Andrew Devare and Claire Moore. All rights reserved)]]

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.

==Parietal Eye==

==Parietal Eye==

 

A well developed parietal "eye" (with a rudimentary lens and retina) is found on the dorsal midline in some lizards, including the green iguana, blue-tongue skink and water dragon. This sensory organ, connected to the central nervous system and the pineal gland by the small parietal nerve, functions in hormone production (including reproduction) and thermoregulation. Although sensitive to changes in light, it cannot form images. Sometimes referred to as "pineal eye" or "third eye", it it visible as an opalescent gray spot on the top of some lizard's heads.

A well developed parietal "eye" (with a rudimentary lens and retina) is found on the dorsal midline in some lizards, including the green iguana, blue-tongue skink and water dragon. This sensory organ, connected to the central nervous system and the pineal gland by the small parietal nerve, functions in hormone production (including reproduction) and thermoregulation. Although sensitive to changes in light, it cannot form images. Sometimes referred to as "pineal eye" or "third eye", it it visible as an opalescent gray spot on the top of some lizard's heads.