The eleventh Symposium of the International Research Group on Colour
Vision Deficiencies (IRGCVD) was held 20-23 June 1991 in Sydney, Aus-
tralia, ably hosted by local organizer Stephen Dain. A total of 35 talks
and 10 posters were presented. Papers based on 37 of these presentations
are included here, in Colour Vision Deficiencies XI. The scientific
program featured sessions on three special topics, with each topic
highlighted by an invited speaker. The opening session on the Genetics
of congenital colour vision deficiencies began with a superb invited
lecture by Charles Weitz about his pioneering work on the molecular
genetics of tritanopia. The session on the second special topic, Spatial
aspects of colour vision, began with the launching of a new IRGCVD
tradition, as 1991 Verriest Memorial Award recipient Harry Sperling
presented the first Ver- riest Memorial Lecture on his recent studies of
spatial discrimination of heterochromatic stimuli. Dr. Sperling reported
new evidence that certain asymmetries in red-green opponent colour
vision can be explained by the spatial organization of colour-opponent
retinal neurons. In the third special session, on Occupational aspects
of colour vision, Barry Cole took the audi- ence on a fascinating tour
of the historical development of colour vision standards in his invited
lecture entitled 'Does defective colour vision really matter?'. In
addition to the three special topics, many interesting presentations
were given in topical sessions on Variations in normal colour vision,
Acquired colour vision deficiencies and Colour vision tests and testing
methods.