An instrument for testing the refractive power of the eye.
- ‘He immediately became hypermetropic (long sighted) in that eye, but using his optometer found ‘the same inequality in the horizontal and vertical refractions as without the water’.’
- ‘We have developed an optometer to measure the ocular astigmatism of human eyes and tested its performance.’
Mid 18th century: from Greek optos ‘seen’ + -meter.
We take a look at several popular, though confusing, punctuation marks.