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测仪，其由单片机、手柄和液晶显示构成，手柄具有上下左右方向等功能键，根据手柄上的按键选取随机出现视标"E"朝向的正确检测视力。