Advertising in the Australian Orthoptic Journal - International ...

36
australian orthoptic journal
exerting or relaxing an appropriate amount of accommodation during
the AC/A ratio measurement. It is well known that the detail of a target
can influence the level of a patient’s accommodation and subsequently
the size of their deviation. Despite this, to date no study has investigated
the effect of different fixation targets on the AC/A measurement in
patients with intermittent exotropia. This study aimed to investigate
the effect of different fixation targets on the near angle of deviation
measurement and AC/A ratio in patients with intermittent exotropia
of the divergence excess type. The incidence of a high AC/A ratio was
also investigated.
Twenty-eight participants identified as having intermittent XT were
included in this study. The size of each participant’s deviation was
measured with a prism cover test at three distances before and after
occlusion. After occlusion, the deviation at near was also re-measured
through plus lenses using two different targets, that of a butterfly and a
N5 print target. The gradient method was employed to measure the AC/A
ratio of each participant. A t- test was used to investigate the difference,
between firstly the deviation measured through plus lenses at near with
the different targets and secondly, if this resulted in a significant difference
in the AC/A ratio measurement.
This study found there was a statistically significant difference between the
two targets used when measuring the deviation, t(54.00)=2.91, p=0.005.
On average, the deviation measured was 8.8∆ larger with the with the N5
print. This also resulted in a statistically significant difference between
the two targets when measuring the AC/A ratio (t(54.00) = -5.139,
p