Chameleons are among the highly visually-oriented lizards, using this sense in prey capture, mating behavior, and predator avoidance. Unique features of chameleon vision include a negative lens, a positive cornea, and monocular focusing. The development of the chameleon visual system could have evolved to aid in prey capture and/or in predator avoidance.
Chameleon eyes feature a negative lens, meaning that the lens is concave. This increases retinal image size, allowing "more precise focusing." In fact, image magnification in chameleons is higher in a scaled comparison to all other vertebrates eyes.
While the lens is negative, the cornea of chameleon eyes is positive, meaning that it is convex. The increased power of the cornea also contributes to a precision in focusing "better than other vertebrates." The cornea improves sight resolution in a narrower field of vision.
The chameleon predator avoidance response is vision-mediated. In predator avoidance, chameleons utilize minimal head movement and a unique method to monitor potential threats.
Photo by kaibara87