Polar

The Polar tab includes various options for setting up a Polarised screen and Polarised mask.  It also includes various options for customising the Random Dot Stereogram test.

If a standard (non-polarised) monitor is being used select None.

If a Polarised Monitor is being used, select Use Polarised Monitor

If a Polarised mask is being used, select Use Polarised Mask.  If this option is selected, a variety of options are available to align the mask,  These are described in detail here.

Random Dot Stereograms (Red/Green)

Test Chart 2016 generates stereograms dynamically allowing a range of optotypes to be generated “in depth” within the stereogram. It also allows stereoacuity to be measured by varying the relative disparity within the stereogram. This process may take a few seconds on slower machines. The number of dots generated, the size of the optotype and the disparity of the background can all be changed via the Polar tab of the Options...General Settings window.

There are a number of vision tests available for measuring stereopsis at near and a rich literature describing norms.  In contrast, there are very few tests capable of measuring stereopsis in the distance and relatively little information about norms and the optimum stimulus parameters.

For this reason Test Chart 2016 allows the user to vary the number/density of dots, the dot size and the size of the character that is seen in depth.  The colours of the dots may also be changed to provide the best match for the screen and red/green visors.  NOTE: The colours are added subtractively to the background and it is recommended that you contact Thomson Software Solutions should you wish to change the colours.

The viewing distance for this test can also be set independently of the viewing distance used for the rest of the program.

Given the paucity of published norms for distance stereopsis, the clinician is expected to develop their own norms for the conditions selected.

Random Dot Stereograms (Polarised)

Equivalent random dot stereograms are available for the polarised monitor.  However, because these require a considerable degree of computation to generate, they are not generated in real time.  Instead, the stimuli are pre-generated and stored as images which load instantaneously.

Test Chart 2016 includes a full set of images for a standard monitor size and viewing distance (6m).  However if a non-standard monitor is used or the viewing distance is changed (or any of the other parameters in the Random Dot Stereogram panel), a new set of images will need to be generated.

To generate a new set of images, select Generate Polarised Random Dot Stereograms.

NOTE:  This process can take up to 30 minutes.