Wesson, "Normalization of prism bar
vergences," Optometry and Vision Science, vol.
Amount of deviation were measured by alternate prism bar cover test, both for distance and near.
Any amount of overcorrection or undercorrection were measured by alternate prism bar cover test.
The test is repeated holding the prism bar in the opposite direction to measure the positive prism fusion range.
This is the point in my evaluation of the patient that I reach for my old friend --a well-used box containing a pair of old-fashioned prism bars. I use these to measure distance and, more often, near prism fusion ranges.
And it certainly wasn't by pretending they had just stepped into Superman's icebound Fortress of Solitude when standing at the Prism Bar
. No, it was by staring in a mixture of awe, disbelief and mortification at the caged dancers who leave very little to the imagination.
(26) A prism from the trial set or a prism bar
is usually held in front of the patient's fixating eye.
* Prism bar cover test--done for near and distance with appropriate refractive error correction appropriate prisms (Base--in/Base--out) The deviation was measured in all the directions of gaze.
* 22 (61.12%) patients had no deviation on prism bar cover test.
On prism bar
cover test there was -55 PD of exodeviation and 4 PD of hypodeviation of the RE with marked amblyopia with central fixation.
Fusional ranges can be measured using a prism bar
or phoropter head.
These are measured using a prism bar
, and the fusional reserve opposing the phoria observed in the cover test should be measured first--for example base out to force convergence in exophoria.