As stated, some coat colors in ferrets are associated with neurological defects, including such problems as blindness or other defects in vision, hearing loss, behavioral changes, loss or deterioration of motor skills, epilepsy, and even mild to severe retardation. Because the timing of eye development takes place so early in the growth of the embryo, vision is rarely impacted, or only to a minor scale (with exceptions). In contrast, hearing is more frequently impacted, with a wider range of problems, because development takes place at a later point of embryonic development. In terms of health impact, because ferrets have been bred for albinism for centuries, most of the nastier problems have long been bred out and visual differences--although profound and represent comparatively deteriorated vision--do not generally change the quality of life experienced by the ferret. There doesn't seem to be major visual problems in ferrets having diluted coat colors or with pointing, and no data for the melanistic ones. Piebald colorations MAY impact vision, but apparently not to any significant degree, and no specific experiments have been reported. The human and the ferret eye are essentially identical in all respects, with a few minor exceptions that reflect different evolutionary histories. Notably among these differences are an area on the retina of humans that allows extremely fine focus to take place (the fovea), a different density and ratio of rods to cones, a reflective layer of tissue behind the retina in the ferret (the tapetum), differences in lens shape and malleability (a far-sighted eye versus a near-sighted eye), a difference in the shape of the pupil (round in humans, horizontal slit in ferrets), and a third eyelid in the ferret (just a fleshy pink area at the inside corner of the human eye). There are other differences, such as the angle of the eye in the bony orbit, but those are influenced by skull anatomy. Some may make the comment that these represent a lot of differences, however, compared to thousands of nearly identical structures in both the human and ferret eye, the differences pale in comparison. Each one of these differences exists because humans and ferrets evolved doing different tasks to make a living. The ferret's eye is adapted to locate prey in dim light (large numbers of rods, tapetum, shape of pupil), while at the same time protecting itself from the types of debris encountered in burrows, running through brush and grass, and from injuries that might occur while struggling with prey or predators (third eyelid). The human eye evolved an area of very sharp focus (fovea), useful in recognizing faces, making tools and finding edible plants, but the ferret uses it's nose for identification, it's whiskers for precise prey location, and it's eyes are adapted to see in dim light, so has little need for such sharp focus. Humans have a far-sighted eye, useful in scanning the horizon, but ferrets have a near-sighted eye, designed to best visualize objects within a couple dozen feet (objects farther away are more noticed for movement rather than precise focus). This is the type of visual adaptation expected from an animal adapted to hunt prey in the dark underbrush and within burrows. It is probable the smell (olfactory sensory organs) and whiskers (tactile sensory organs) are adapted for hunting, while sight (visual sensory organs) is adapted to detect predators, which would explain why polecats are periodically found in large owl pellets, and the number one predator of polecats throughout Europe (and ferrets in New Zealand) are automobiles--neither are visually noticed until it is too late. The proportion of rods to cones in the ferret shows high adaptation of the eye to work in dim lighting conditions. Rods are very sensitive to light but (in most cases) produce little color information and do not produce a very sharp image compared to cones. Cones require high levels of light, and produce color information as well as shaper images than rods. The bottom line is that the ferret sees more or less the same as humans, but that vision is somewhat grainier, has little color information (most reds and some blues), is nearsighted, and cannot bring objects into super-fine focus (Gosh, expect for seeing in color, I think I have ferret vision!). Compared to humans, ferrets are somewhat colorblind, but since ferrets are domesticated polecats, and polecats hunt mostly by smell, not being able to see some colors is unimportant. Bob C [Posted in FML issue 4256]