Cone mosaic observed directly through natural pupil of live vertebrate.

Using a simple ophthalmoscopic technique, the cone mosaic of a live garter snake was clearly visible when viewed directly through its natural pupil, providing the first definitive cone map in a vertebrate eye. The optical MTF was also measured in natural conditions by projecting gratings in the snakes' field of view. Marrying these two results gives, unequivocally, the interrelation of optical image quality and the photoreceptor mosaic.