− | A well developed parietal "eye" (with a rudimentary lens and retina) is found on the dorsel 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. |
− | They are usually present although some geckos and the oscellated skink (''Ablepharus sp.'')have snake-like spectacles. | + | They are usually present. The lower lid is movable, moving upwards to close the eye; in some lizards, this lid might be transparent, allowing vision even when the lids are closed. Lizard also have a well developed, semi-transparent, highly mobile third eyelid which is called the 'nictitating membrane'; this membrane can close across the eye even while the eyelids remain open. |
− | In some chameleon species, the eyelids have fused to produce a circular, immobile and transparent dermal aperture called a spectacle. It create an impervious barrier to topically applied medications. Lizard species lacking a spectacle have a well developed, semi-transparent, highly mobile third eyelid which is also called the 'nictitating membrane'; this membrane can close across the eye even while the eyelids remain open. | + | In some chameleon species as well as some geckos and the oscellated skink (''Ablepharus sp.'') the eyelids have fused to produce a circular, immobile and transparent dermal aperture called a spectacle. It create an impervious barrier to topically applied medications. |