Vergence Prism With Stainless Steel Stick

Vergence Prism test is used to assess the ability of the fusional vergence system to respond rapidly and accurately to changing vergence demands over time. This is measured in number of cycles per minute (cpm) that a stimulus can be fused through, alternating base-in (BI) and base-out (BO) prisms. 

 

Vergence facility response can be  tested over a 1 or 2 minute period at 40 cm using a single flip prism, 3 delta BI/12 delta BO, which has been found to differentiate optimally between groups at distance and near. 

 

This prism change is repeated for one minute and the clinician records the number of cycles performed during testing. Presence of suppression is indicated by a perceived lateral movement of a single target moving left or right of center, or no observed eye movement.

 

Most normal patients can cycle between these prism at the rate of 15/cpm. Those with difficulty should be more thoroughly tested. Repeatability of test results (with the 3 delta BI/12 delta BO prism) can be poor at distance and good at near.

 

Vergence Facility Prism combines 12D BO and 3D BI and  is 1 1/2 inch high (38mm). Available loose or mounted on stainless stick.