optometer การใช้

When the optometer and phorometer were combined into single instruments, the modern competing versions.
The term " optometry " comes from the Greek words " optometer, ( before the terms phoropter or refractor were used ).
A phoropter is one of several generic names for modern instruments containing an optometer ( battery of lenses for determination of optical error ), combined with prisms and other attachments for measuring binocularity.
Optometer was the generic name for devices, crude and simple, with rotating batteries of sphere and cylinder lenses placed in front of each eye, one at a time, so there was no testing for binocularity.