| 摘要 |
An improved visual acuity tester is disclosed that is adapted both to measure the visual acuity of a patient and to function as an integral optical prescription calculator. The visual acuity tester essentially includes a display monitor for displaying visual acuity targets, electronic means for generating a plurality of visual acuity targets to be displayed on the monitor, and a hand-held remote control unit provided with a display unit and a keyboard coupled to the electronic means for controlling the display on the monitor and for performing prescription calculations. The visual acuity targets are created by toggling on/off the electronic means when horizontally scanning the lead lines of screen memories of the targets. Preferably, the electronic means includes a dynamic memory having two screens of memory: an active screen and an inactive screen. The active screen is displayed on the monitor and the inactive screen is being erased, both being constantly accessed at short intervals for memory refresh and erasure. Preferably, the visual acuity tester is provided with a contrast control for low contrast testing. The visual acuity tester is adjustable for straight refractory distances from about ten to about twenty feet in length. With a mirror, it also can be fitted to a shorter refractory lane.
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