In order to test binocular vision (i.e. coordination between the left and right eye) it is necessary to present a slightly different picture to each eye. There are various ways of achieving this in a vision testing device.
The Binoptometer® 4P uses a shutter system for image separation. The shutter system can also be used to cover up the eye that’s not being tested. It consists of a split plate with two liquid crystal surfaces (one for the right and one for the left eye) that is integrated into the unit. The liquid crystal surfaces can be electronically switched between a light-transmissive and a non-light-transmissive state. This makes it possible to virtually cover up the right or left eye as desired.
With this setup of the Binoptometer® 4P an examinee’s binocular vision can be tested by alternately presenting images to the left and right eye on the unit’s high-resolution display. The shutter plate switches synchronously so that each image only reaches the eye it is intended for. This switching back and forth happens at a very high frequency that cannot be perceived by the human eye. If you alternately close your right and left eye during a phoria test on the Binoptometer® 4P you will see two different images.
