A bit of info on eyesight please?

[Stefan-A]

The photoreceptors and visual pigments of the garter snake
(Thamnophis sirtalis ): a microspectrophotometric, scanning
electron microscopic and immunocytochemical study

The presence of more than one cone pigment satis®es
the most basic retinal requirement for wavelength dis-
crimination or color vision. Unfortunately, we know of
no reports describing any color vision capability, or lack
thereof, in any snake species. Color vision is so common
among the vertebrates (Jacobs 1981) that it would not be
unreasonable to assume that the garter snake has color
vision. However, the assumption would be premature
without direct experimental data since a multipigment
system can serve other functions, such as simply
increasing sensitivity across a broad spectral range or
enhancing contrast (Lythgoe 1979).

[guidofatherof5]

The photoreceptors and visual pigments of the garter snake
(Thamnophis sirtalis ): a microspectrophotometric, scanning
electron microscopic and immunocytochemical study

Thanks Stefan. I thought it was you but didn't trust my memory.