This chapter describes a technique that utilises established usability evaluation techniques to discover a range of accessibility requirements for digital TV (DTV) viewers with low vision. A study was reported in which two “stalking horse” prototype conditions were tried by subjects performing interactive tasks. These prototypes were not developed technologies but Wizard-of-Oz style conditions. In one condition subjects were asked to use gestures to interact with DTV services, with the screen responding to their hand movements. The other condition used a static keyboard display placed on the table in front of them. Their role was both to probe the efficacy of these approaches and to prompt rich information relating to the subjects abilities, lifestyles, and strategies for interaction. The reported study analyses four viewers with differing types of sight impairment. .The reported study was successful in yielding both general concerns about current approaches to DTV display and interactivity design as well as giving significant insights into the possible potential of and difficulties with alternative input methods. The sessions yielded numerous critical incidents, examples of which are reported and analysed. The format also yielded key insights into the way in which individual viewers compensate for diminished vision by using alternative skills such as touch-typing and alternative sensory signals, inductive reasoning and heuristics. The significance of these insights for DTV design and accessibility support is then discussed.