As the amount of readily available reading material increases, the ability to read selectively, or to skim-read, is becoming an important skill. In this paper, we report a comparative study of existing skim-reading strategies in sighted and visually impaired individuals. Using a think-aloud approach, we identified key features of visual documents that allow sighted users to adopt a highly flexible and goal-oriented approach to skim-reading. These features are mostly lost when documents are accessed in auditory form, as is commonly the case for visually impaired individuals. As a result, this group has to fall back on either less efficient or cognitively more demanding exploration strategies. From our results, we propose a list of six design implications to guide the development of future technologies assisting non-visual skimming.