Purpose:
We have previously shown that binocular subjects perform significantly better than monocular subjects when undertaking hand-eye coordination tasks at near. However it is unknown whether reduced stereopsis is beneficial, compared to none.
Methods:
Stereoacuity was measured using TNO. Fine motor skills were assessed by 4 methods: Purdue Pegboard (number of pegs placed in holes in 30 secs), threading large beads onto a large needle (number of seconds to place 30 beads), threading small beads onto a small needle (number of seconds to place 22 beads), pouring water from a jug into 5 separate cylinders aiming to fill each cylinder to 90ml (time taken and accuracy). Binocular subjects were tested with and without occlusion. Stereoacuity was graded into normal (≤60"), reduced (>60") and none measurable.
Results:
Analysis of variance showed a significant difference between the graded stereoacuity outcome and the results from the Purdue Pegboard, large and small beads and the error in the water pouring task (see table). Both bead tasks had a graded response with increasing stereoacuity resulting in an improved response to the task. On the Purdue Pegboard only the highest level of stereoacuity was associated with an improved response. On the cylinders task normal and abnormal stereoacuity had a similar outcome and were both better than no measureable stereoacuity. A comparison of the outcomes of the binocular subjects when occluded (short term monocular group) and the subjects with no measurable stereopsis (long term monocular group), showed that only the large bead task (t-test, p=0.032) and purdue pegboard (t-test, p=0.025) demonstrated an improvement in the long term compared to the short term monocular group.
Conclusions:
There is a benefit to lower grade stereoacuity in some scenarios, but it is task dependent. Two tasks showed a degree of adaptation to the long term absence of stereopsis, but in most tasks there was no significant difference between the long and short term monocular groups.
Keywords: binocular vision/stereopsis