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4) Workgroup for the International Society for Low Vision Research and Rehabilitation: Guide for the Evaluation of Visual Impairment. San Francisco, Calif: Pacific Vision Foundation; 1999. Available as PDF at: www.ski.org/Colenbrander.Accessed May, 2007.
5) International Council of Ophthalmology (ICO):Visual Standards, Aspects and Ranges of Vision Loss with Emphasis on Population Studies. Mel-bourne,Australia:ICO;2002. Available as PDF at:www.icoph.org/standards. Accessed May, 2007.