The eyes of different breeds of dogs

Like most mammals, dogs are dichromats and have color vision equivalent to red–green color blindness in humans (deuteranopia).[113][114][115][116] So, dogs can see blue and yellow, but difficult to differentiate red and green because dogs only have two spectral types of cones photoreceptors, while normal humans have three cones. And dogs use color instead of brightness to differentiate light or dark blue/yellow.[117] Dogs are less sensitive to differences in grey shades than humans and also can detect brightness at about half the accuracy of humans.[118]
The dog's visual system has evolved to aid proficient hunting.[113] 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[113]), their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g., identifying their human guardian) at a range of between 800 and 900 m, however this range decreases to 500–600 m if the object is stationary.[113]
Dogs have a temporal resolution of between 60 and 70 Hz, which explains why many dogs struggle to watch television, as most such modern screens are optimized for humans at 50–60 Hz.[118] Dogs can detect a change in movement that exists in a single diopter of space within their eye. Humans, by comparison, require a change of between 10 and 20 diopters to detect movement.[119][120]
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.[113] The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. There is also a relationship between body size and overall diameter of the eye. A range of 9.5 and 11.6 mm can be found between various breeds of dogs. This 20% variance can be substantial and is associated as an adaptation toward superior night vision.[121]
The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations.[122] 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, in particular, 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