Staring into the Hypnotizing Eyes of Cold-Blooded Reptiles
Red eyed lizard to look like dragon
Snakes use a combination of infrared vision (developed in the trigeminal nerve), variable (by species) visual acuity and color detection, limited eye mobility, and chemosensation to find prey and recognize features in their environment (including their keepers).
Lizards (including geckos) and turtle retinas contain multicolored oil droplets in their photoreceptors, so they can perceive color. The opsin proteins in the cones in the eye are “calibrated” to detect different wavelengths. In many species, this enables them to see into the higher wavelengths beyond the scope of unaided human vision: into the UV range.
Nocturnal reptiles usually have smaller eyes than diurnal ones, but relatively large pupillary and lens aperture and cornea. This improves their light-gathering ability, but at the same time reduces visual acuity.
The scaly eyelids of chameleons are cone-shaped, and only the pupil really shows through in the circular opening created. Photo: Umberto Salvagnin
Tokay gecko are nocturnal and have slit pupils set in large eyes – the color of which range from brown through greenish brown to yellow and orange.
Chameleons have 360-degree vision, with each eye able to move and focus separately. They can thus look at two different objects simultaneously.
Green Tree Monitor Lizards have sharp vision, with large, round pupils that let in a lot of light.
This Australian bearded dragon lizard can see in color; in fact, the cones in the eyes of many species allow them see beyond the spectrum of human vision.
A Brazilian lizard, Enyalius iheringii whose large round pupil is brilliantly contrasted with its green scales. Photo:João P. Burini
The bearded dragon, which has photosensitive eyes, will react to shadows to let the ‘beardie’ know if there is a threat from above.