Biomedical Engineering Reference
In-Depth Information
an interesting aspect, however not a question of this subject. Let us take note
and recognise the fact that the available tactile performance is used differently
depending on the environment conditions.
1.2.2 The Visual Acuity
The use of the vision system in different situations to discover, detect, track or
follow the course of events, is considered of vital importance for man, and has
always been a major quality in surviving a hostile world. In previous generations
however, humans have entered into an evolutionary phase consisting of partly
different challenges. The fact that we do not have to make use of the visual profi-
ciency in our daily lives for survival noticeably increased in the last decades. The
observation can mainly be related to the change of living conditions that pervades
our lifestyle. The change in lifestyle has provided us with circumstances that are
not needed anymore and we have to adapt to new conditions.
In the literature, a number of investigations can be found regarding adult pop-
ulation studies, showing that better visual acuity is generally confirmed at all ages
and more so in men than in women, e.g., Robaei (2005). Also the age-related
change in contrast is confirmed, e.g., in the Nomura (2003) study.
Among young people, a clear gender difference among children has not been
firmly established in the literature, as reported by Robaei (2005). However, these
results contrasts new findings revealing a significantly higher prevalence of visual
impairment among girls in a Chinese study, He (2004). In contrast, the studies
from South Africa, Naidoo (2003) demonstrated a higher prevalence among boys.
This clearly confirms the need to conduct further research in this area that may
clarify the differences.
This may, in fact, show other findings that are due to the greater variability of
visual acuity gender and social activities between boys and girls. This indicates,
among other issues, a socially different development phase in combination with
geographical differences in populations between young men and young women.
The studies of ethnical and regional differences is also represented in the lit-
erature. The study from Merritt (1996) found for example, a lower prevalence of
subnormal visual acuity in white Americans than in African Americans. Regional
differences are indicated in a number of studies from different countries. For
example, a low overall rate of visual impairment probably indicates a very low
prevalence of myopia among six-year-old Australian children. The myopia preva-
lence can in the different regional differences vary as much as 20 % in similar age
tested groups in Taiwan and Singapore, Robaei (2005).
Furthermore, these findings are according to the study consistent with the
prevalence of myopia in Australian older adults, which also has been reported
to be lower than among adults in Europe and the United States. Whether these
regional differences are due to unique environmental influences remains to be
determined. As usual, further studies into this area, could of course provide
important information regarding the visual degradation in populations.
Search WWH ::




Custom Search