[vslist] Vision in the twlilight zone - abstract deadline

[Helen Walkey]

This is a reminder that the abstract submission deadline for the UK 
symposium on mesopic vision: "vision in the twilight zone" is Monday 16th 
August.

Details of the abstract submission procedure can be found under the heading 
Research Meetings and the link to More Information, at 

http://www.city.ac.uk/avrc/
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Symposium description:


Meeting of the Colour Group of Great Britain:

VISION IN THE TWILIGHT ZONE: STUDIES OF VISUAL PERFORMANCE 
UNDER MESOPIC CONDITIONS
 
Applied Vision Research Centre,
The Henry Wellcome Laboratories for Vision Sciences,
City University,
Northampton Square,
London, UK,
EC1V 0HB
 
Thursday 11th November 2004


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The human visual system functions over a range of light intensity  
spanning approximately 10 log units. Operation over such a large range  
is possible largely through processes of adaptation. Much of this is due  
to the dual nature of the human retina; we have two types of  
photoreceptor, cones that operate at higher light levels and rods that  
operate at very low light levels. Mesopic vision describes the transition  
region from cone vision (photopic vision) to rod vision (scotopic  
vision), in which signals from both rods and cones contribute to the  
visual response. Many changes occur in this transition region that affect  
visual performance. Colour vision deteriorates as a result of reduced  
cone photoreceptor signals. The involvement of rod signals causes the  
spectral sensitivity of the eye to change, which has consequences for the  
measurement of luminance. At present there is no measure of luminance  
that reflects the spectral sensitivity of the eye in the mesopic range.  
Changes in pupil size alter the optics of the eye, resulting in changes in  
the quality of the retinal image. Differences in the operational  
characteristics of rods and cones lead to changes in spatial and temporal  
resolution as well as absolute sensitivity. Although the rod and cone  
systems are generally considered to operate independently, it is well  
known that many observed effects can only be explained in terms of rod- 
cone interactions. Work environments where the visual system has to  
perform, at least in part, under mesopic conditions are not uncommon.  
Some examples are: driving road vehicles/driving trains/flying  
aeroplanes at low light levels, security services/police surveillance work  
at low light levels, construction work at low light levels (some  
roadworks are now carried out at night). Little attention has been paid  
to understanding how visual performance changes under mesopic  
conditions. This one-day symposium aims to address the question of  
whether visual performance data can be used to describe mesopic light  
levels, and to explore the properties of vision at low light levels in order  
to gain a better understanding of the limits of visual performance in the  
mesopic range.  

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