The foveal system of the human eye is the only part of the retina

Retina

The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 that permits 100% visual acuity. The line-of-sight is a virtual line connecting the fovea

Fovea

The fovea centralis, also generally known as the fovea , is a part of the eye, located in the center of the macula region of the retina....

 with a fixation

Fixation

Fixation may refer to the following:In science:*Fixation , the state in which an individual becomes obsessed with an attachment to another human, an animal, or an inanimate object...

 point in the outside world.

The discovery of the line-of-sight is attributed to Leonardo Da Vinci

Leonardo da Vinci

Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...

.

His main experimental finding was that there is only a distinct and clear vision at the line-of-sight, the optical line that ends at the fovea. Although he did not use these words literally he actually is the father of the modern distinction between foveal vision (a more precise term for central vision) and peripheral vision

Peripheral vision

Peripheral vision is a part of vision that occurs outside the very center of gaze. There is a broad set of non-central points in the field of view that is included in the notion of peripheral vision...

.

Leonardo DaVinci, (1452-1519) was the first person known in Europe to recognize the special optical qualities of the eye. He derived his insights partly through introspection but mainly through a process that could be described as optical modelling. Based on dissection of the human eye he made experiments with water-filled crystal balls. He wrote "The function of the human eye, ... was described by a large number of authors in a certain way. But I found it to be completely different."

The modern diagram to the right shows that the fovea is a sort of pit. The Latin word fovea actually means pitfall.