Sighthound

A sighthound also called gazehound is any member of a grouping of dog breeds classified based on their exceptional visual ability. A common definition is that sighthounds hunt by sight rather than by scent, but this is misleading, as a sighthound will use its senses of smell and hearing when hunting, just as any other dog will.

The sight hounds have been specifically bred to capitalize on their use of vision in tracking prey; some of the breed types are ancient. These include the Greyhound and Afghan Hound.

Background: dog sight vs. human sight

Because the lenses of dogs' eyes are flatter than humans', they cannot see as much detail; on the other hand, their eyes are more sensitive to light and motion than humans' eyes. The most capable sighthounds have a field of vision up to 270° (compared to 180° for humans).

It was formerly thought that all dogs had the same eye structure, as humans do. However, recent research has shown that the eye structure, including the retina and the proportionate size and shape of the eyeball, differs significantly among dog types. Further, we now know that dogs are not colourblind, as was previously believed, they simply have trouble with the colour red.