Peripheral refraction along the horizontal and vertical visual fields in myopia.

Peripheral refractions were measured to 35 degrees eccentricity using a free-space autorefractor in young adult emmetropic and myopic subjects. Refractions were measured along horizontal and vertical visual fields for 116 subjects and a 43 subject subset, respectively. Along the horizontal visual field, peripheral myopic shifts in spherical equivalent M of emmetropes changed to relative hypermetropic shifts in the myopes, there were temporal-nasal asymmetries of 90 degrees to 180 degrees astigmatism J(180) which decreased as myopia increased, and 45 degrees to 135 degrees astigmatism J(45) was linearly related to field angle. Along the vertical visual field, both peripheral myopic shifts in peripheral M and J(180) asymmetry were unaffected by magnitude of myopia, and J(45) changed at three times the rate as for the horizontal visual field. Myopia has more effect on peripheral refraction of adult eyes along the horizontal than along the vertical visual field. The peripheral variations in refraction match well what is known about the shapes of emmetropic and myopic eyes.