| 摘要 |
<p>The ophthalmic device measures the spacing between the left and right pupils via a pair of light beams, which are projected directly onto the cornea of each eye. Each beam provides an fine sharply defined optical mark on the cornea, the position of these being adjustable, so that the pupil spacing is provided by the required amount of adjustment read from a scale. Pref. the patient rests the bridge of his nose on a support at a given distance from the device. The respective beams are directed onto the right and left eye, one at a time with the other beam being blocked via an opaque disc. The optical mark provided by the beam is adjusted between two limits, so that it is aligned with the centre of the pupil, by rotation of an adjustment knob allowing parallel shifting of the beam. The spacing between the pupils is determined from the amount of adjustment of each beam, which may be read from a combined scale. the measurement is free from parallax errors and is not dependendent on the distance between the pupils of the person performing the testing.</p> |
