Senses Sight

Senses
Sight
A Greyhound, one of many breeds of sighthound.

Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness in humans (deuteranopia).[91][92][93][94]

The dog's visual system has evolved to aid proficient hunting.[91] While a dog's visual acuity is poor (that of a poodle's has been estimated to translate to a Snellen rating of 20/75[91]), their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g. identifying their owner) from distances up to a mile.[91] As crepuscular hunters, dogs often rely on their vision in low light situations: they have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum.[91] The tapetum is a reflective surface behind the retina that reflects light back to give the photoreceptors a second chance to catch the photons.

The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations.[95] Many long-nosed breeds have a "visual streak" – a wide foveal region that runs across the width of the retina and gives them a very wide field of excellent vision. Some long-muzzled breeds, particularly the sighthounds, have a field of vision up to 270° (compared to 180° for humans). Short-nosed breeds, on the other hand, have an "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans.[92][93] Most breeds have good vision, but some show a genetic predisposition for myopia – such as Rottweilers, where one out of every two has been found to be myopic.[91]





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