He was also found to have astigmatism (a rugby ballshaped cornea) and a fixation disparity
, which means he had problems focusing his eyes together.
Orthoptists do not refract or measure fixation disparity
(sensory fusion) or understand the physiology of normal binocular vision, which is intimately related to the accommodation vergence reflex.
These systems comprise diagnostic programs to assess phorias, fixation disparity
, fusional vergences and suppression, motor fields, pursuits and saccades, while therapeutic programs provide tasks to treat ocular motility, vergence and accommodative disturbances.
d I t measures the aligning prism/sphere that eliminates the fixation disparity
In sports such as tennis, where the primary sporting skill is depth perception, it doesn't matter which eye has the fixation disparity
(FD) as long as the FD is corrected to maintain stereopsis.
You can now control your chart remotely from an iPad, iPhone or Android device and hand the device to the patient to perform near tests, including fixation disparity
d Spectacles with low positive power to eliminate fixation disparity
On the Mallett Unit, note that it is not always possible to align the bars perfectly as some fixation disparity
curves do not pass through a null point.
a) Neutralise the deviation and check fixation disparity
for far vision
If the symptoms and cover test suggest a possible decompensated heterophoria, the next step would be to carry out the Mallett unit fixation disparity
Particular factors considered in this study were age, sex, visual acuity (VA), ocular dominance, binocular vision, stereoacuity, accommodation, convergence, refraction, and fixation disparity
It is probably true to say that the Mallett unit fixation disparity
test has revolutionised the diagnosis of decompensated heterophoria in primary eye care in the UK.