Visual acuity is typically measured while fixating, i.e. as a measure of central (or foveal) vision, for the reason that it is highest in the very center.). However, acuity in peripheral vision can be of equal importance in everyday life. Acuity declines towards the periphery first steeply and then more gradually, in an inverse-linear fashion (i.e. the decline follows approximately a hyperbola). The decline is according to "E"2/("E"2+"E"), where "E" is eccentricity in degrees visual angle, and "E"2 is a constant of approximately 2 deg. At 2 deg eccentricity, for example, acuity is half the foveal value.