Wide distribution of external local sign in the normal population

The extent of the apparent visual Weld was determined for a group of 78 naïve visual observers. We Wnd that there exists a minority (less than 10%) that is essentially veridical, but that the majority of the population experiences an apparent visual Weld of only about 90°, thus much narrower than the dioptrics of the eye would suggest (a little over 180°). This is in good accordance with available (albeit mainly anecdotal) evidence, though formal data have been lacking thus far. The Wnding is discussed in the context of metrical calibration of the topological structure of the visual Weld, an aspect of “local sign”