These high quality prisms are used to measure the deviation in strabismus. Prisms provide an efficient means for treating cases of diplopia, symptomatic heterophorias and abnormal head postures.  

 

Prisms can be very useful when treating patients with symptomatic binocular vision disorders, but opinions vary widely about how to best determine the amount to prescribe. Indeed, common methods for determining prismatic prescriptions can result in different magnitudes of recommended prism for the same patient. This lack of consensus, along with rough guidelines and apparently contradictory rules of thumb, may make some clinicians uncomfortable prescribing prism and may even deter them for doing so.

 

Some report that Prisms tend to be more effective for patients with divergence insufficiency, basic esophoria, and vertical heterophoria than for convergence insufficiency, basic exophoria, divergence excess and convergence excess.