The associated phoria test is similar to the fixation disparity test except the size of the disparity is measured rather than the prismatic power to overcome the disparity. The two values are not well-correlated.



Screen for measuring horizontal associated phoria


The patient views the display through the red/green filters. The grey green and its surround are seen by both eyes while the red and “green” bars are seen by the left and right eyes respectively. The patient is asked if the two lines appear to be in a straight line. If they are not, they may be displaced horizontally using the Vertical Scrollbar on the Control Window or using the vertical cursor control keys on the keyboard or remote, until they appear to be aligned.


The displacement of the bars is displayed in units of prism dioptres. This measurement is based on the screen size calibration and the viewing distance and so it is important that these are accurate.


This procedure may then be repeated with horizontal lines in order to measure the size of any vertical deviation. When the Associated phoria test is selected, the following options are available:



Screen for measuring vertical associated phoria



Summary

Mouse

The separation of the bars may be changed using the vertical scrollbar on the Control Window,







Keyboard

Use the vertical cursor control keys to change the separation of the bars





Remote


Use the vertical arrows to change the separation of the bars