Summing up the literature, the quality and the availability of
visual feedback affect the accuracy of manipulation actions. A lack
of visual feedback may, in part, be compensated for by spatial
memory. The contribution of spatial memory to motor performance
has been investigated only for durations lasting a couple of
seconds. It is therefore unclear, to what degree spatial memory
may support motor actions for durations such as those involved in
a self-testing visual screening. In the case of a simple test procedure,
visual screening by means of self-testing instruments lasts
several minutes (Menozzi, 2013). Durations of up to tenths of
minutes are possible when sophisticated tests are adopted.
Considering a vision test requiring the discrimination of eight
orientations, as stated by the ISO 8596:2009 standard procedure
for acuity testing, an accuracy of