Fixating on comfortable vision

Fixation may be defined as the amount of deviation from fixation that still allows single binocular vision. It depends upon the flexibility offered by Panum’s areas which allow for a slight misalignment of fixation. For a review of fixation disparity and its assessment, see page 24 of this issue.

Fixation disparity will occur when the fusional reserves of the binocular system may struggle to maintain single binocular vision when a phoria is present. As such, it may be used as an indication of the phoria being decompensated. As decompensated phorias lead to symptoms of visual discomfort, blur and transient diplopia, then they are of significance to the practitioner and should be addressed.