dioptre
noun [ C ] physics, medical UK specialized (US diopter) uk/daɪˈɒp.tər/ us/daɪˈɑːp.tɚ/
屈光度，折光度
a unit of measurement of the power of a lens, used for measuring a person's eyesight
A typical short-sighted person in Britain is -4.5 dioptres. 在英国，典型的近视眼是 -4.5屈光度。