Fresnel trial sets are indispensable as a tool for the
proper evaluation of ocular motility disturbances.
These acrylic prisms allow for a more accurate
evaluation of large-angle deviations.
Because a rigid Fresnel prism reduces vision less and
creates less distortion and aberration than the press-on
prism of a corresponding power, the practitioner can
more accurately determine the tolerance to a given
The patient who is not able to tolerate a prism from the
trial set due to its side effects would not be a good
candidate for a Fresnel press-on prism.