Strabismus PD  


 V2.0  download   2008/08       

 V2.1  download   2013/01  


The program is designed for clinic use to evaluate the Prism Diopters (PD) required for a strabismus (wall eye, cross eye or vertical deviation) patient (tester), by using red/blue or red/green filter glasses.


Prism Diopter is the unit measuring the deflection of light passing through a prism equal to a deflection of 1 centimeter at a distance of 1 meter.


The filter, each eye can only see one of red, blue or green light.


The tester should set 60cm in front the screen (eye to screen) with the filter. With his/her eye face the screen center.

Instruct the tester to move the mouse to put the cross cursor in the center of the circle target, then left click.


The examiner record the Prism deviation value show in the right up corner of screen, after that examiner should random move the mouse, and let the tester to do it again. Due to fusion ability, different initial direction may have different PD.

BL: 2.6 = Prism Base Left 2.6 diopters  (BR= Base Right)

BD: 1.3 = Prism Base Down 1.3 diopters (BU= Base Up)

OS = Left eye on green cross cursor (Right eye on red circle Target, Right eye is Fix eye)


Right click the mouse or press ESC key to exit to program menu.


User manual


l         Select the Filter to match your filter glasses.

l         If the tester has Dominate Eye, Select the dominate eye as Fix eye.    

l         By default, the Target is in center, and the measure range is +- 30PD horizontal, +-24 PD vertical depend on size of your screen. For test more than 30PD horizontal, you may locate the target at right quarter or left, which may enlarge the range to 45 PD or more.



l         Run the program, press the “Calibrate” button.

l         Press scroll bar to move the cursor 150 mm from the corner (25 PD)

l         Calibration is need only the first time you run this program on a new screen. The values will keep in strab.ini file.




Minimum System requirement:

l         PC with Windows OS

l         19 inches or larger screen, resolution 1280*1024 or more, with black screen frame or cover the screen frame with dark color paper tape.

l         At least one mouse, two mice is recommend, one for examiner, one for tester (disable the right click)

l         The testing should be run in dark room

l         Red / blue or red / green filter glasses



For Large screen:

For large screen, and the seat is not 60 cm from screen.

You should recalculate the “equal length“ of the X & Y lines for calibrate intead of 150 mm 

For example:

  A. seat 1 meter from the tester:

    equal length of the X & Y = 150 mm * (1m/60cm ) = 250 mm on your screen (25 PD)

  B. seat 2 meter from the tester:

    equal length of the X & Y = 150 mm * (2m/60cm ) = 500 mm on your screen (25 PD)




With the tester head tilt, head turn, chin up/down, plus power glasses, there are more interesting information attended, an auto diagnostic suggestions may come out , with cranial nerve palsy, over AC/A, progress of thyroid ocular myopathy….


Download site:

Bugs Report: please email to


Philip Sun


Knowing bugs:

1. When the cursor at target left top point, the cursor may transfer to traditional “cursor point” for a moment, not solution yet. (2008-08-10)