This article may be downloaded for personal use only. Permission to reproduce this article must be sought from Orthoptic Association of Australia. This article was first published in Australian Orthoptic Journal, 41(1): 7-12, 2009. More information about this publication may be found at http://www.orthoptics.org.au/resources/australian-orthoptic-journal/
Copyright (2009) Orthoptic Association of Australia. Reprinted with permission.