random sample

Methods The optometer is composed of singlechip, handle and LCD.The eyesight is examined by selecting exposure of random sample eye-chart mark E within direction keys on the handle.

采用微计算机控制视力检，由单片机、手柄和液晶显示构成，手柄具有上下左右方能键，根据手柄上的按键选取随机出现视标"E"朝的正确与否来检视力。