Three binocularity evaluation methods.

Determining effort expended in binocular seeing is usually accomplished by equating dissociated phoria with total vergence ability. Fixation disparity testing by disclosing failure of precise binocular alignment is a second method which helps to assess both direction and quantity of prism power needed to accomplish alignment. Neither of these two methods delineates the foveal role as a sensory fusional lock in binocularity. The third is the Goodlaw test in which the exact focus of the eyes is disturbed through plus and/or minus lenses, provides this information and further directs therapy.