Escalas Prismáticas #
The last section of Binocular Vision is dedicated to Incomitance tests to evaluate ocular deviation, especially in patients with diplopia.
Firstly, we have a prismatic scale to measure horizontal deviation, and another for vertical deviation, which are used with the red/blue filters (red filter in front of the right eye, OD), so that the OD observes the blue arrow and the left eye observes the red scale. The prismatic scale is calibrated for the viewing distance we have defined in the program’s settings. The range of measurement will depend on this viewing distance and the dimensions of the screen. For example, for a 23″ screen and a viewing distance of 4 meters, the range of the prismatic scale goes from 6 prism diopters of Exo to 6 of Endo on the horizontal scale; and from 3 of Hyper to 3 of Hypo on the vertical scale.
Tools Menu #
The tools menu includes a pair of zoom icons to increase and decrease the size of the numbers and the blue arrow by a factor of x1.25 (or using the “+” and “-” keys).
There are also 2 icons to increase or decrease the thickness of the blue arrow (or with the key combination “Ctrl Shift +” and “Ctrl Shift -” respectively).
The size we have chosen in the last execution of the program will be saved for the next session.
To help the patient locate the blue arrow, we can make it blink on the screen for 3 seconds by pressing the icon in the tools menu, or the “F” (Flicker) key on the keyboard.
Use #
The horizontal and vertical prismatic scales are useful in incomitant deviations with diplopia. They allow us to measure the deviation at any distance, to determine the prism that compensates for diplopia in the primary direction of gaze.