This presentation concerns the growing needs of a subset of computer users with visual impairments, those who have been diagnosed with Age-related Macular Degeneration (AMD), the leading cause of blindness in adults 65 years and older. Participants diagnosed with AMD and visually healthy, age-matched controls completed a series of visual search, icon selection and manipulation tasks on either a desktop or a handheld PC. Participants searched, selected and manipulated familiar playing card icons under varied icon set sizes, inter-icon spacing, icon sizes and auditory feedback.

A comprehensive account of the interaction was made using a collection of efficiency, accuracy and information processing metrics. While all participants demonstrated a high rate for successful task completion, analyses revealed participants' overall task efficacy to be coupled with features of the interface, success rates were also strongly linked with measures of ocular health and personal factors. The outcomes of this study contribute to a growing body of work which informs a framework of performance thresholds for critical graphical user interface interactions based on visual profile, interface features and supplemental non-visual cues. In addition, several notable results extend the existing knowledge base of human computer interaction, aging and visual impairment including:

• The impact of auditory feedback on task interaction and information processing for visually impaired versus visually healthy older adults;
• The observed use of the mouse pointer or stylus as means to direct attention during visual search and the implications of manual dexterity on visual search;
• The presence of speed accuracy trade-offs in handheld PC interaction performance for individuals based on their contrast sensitivity and near visual acuity;
• The shifting impact of increased icon spacing on visual search and movement times, versus its role in the accuracy of icon release;
• The utility for non-clinically acquired summaries of visual health to effectively predict performance decrements in handheld or desktop interaction;
• Emergent differences between handheld and desktop interaction and the most influential visual factors informing performance on each; and
• Empirical evidence that older adults, even with visual impairments can interact with small handheld displays, in spite of small image sizes.

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