A CASE STUDY: WEB INTERACTION OF TOTALLY BLIND PERSONS

Numerous user studies suggest that the totally blind encounter more difficulty than those with other sensorial disabilities (such as low vision, motor or hearing impairments) when executing specific tasks (Petrie, Fraser & Neil, 2004; Craven, & Bro- phy, 2003; Ivory, Yu & Gronemyer, 2004). Petrie et al. presented the results of accessibility testing of 100 websites with users with visual, motor and perceptual disabilities, showing that websites that are accessible for differently-abled users can also be visually pleasing. Specifically, 100 websites spread out over five sectors were tested with automated verification and user testing, involving 51 differently-abled users, including 10 totally blind users. Results showed a mean task success rate of 76% that goes down to 53% considering only the totally blind (the lowest score of all the user categories). Likewise, regarding user satisfaction, the authors recorded that the blind encountered more difficulty than other differently-abled users (4.2 on an 1…7 Likert scale, the lowest score of all the user categories). Researchers at Manchester Metropolitan University (Craven & Brophy, 2003) highlighted issues of non-visual access by studying a sample of blind and visually-impaired users who performed four information-seeking tasks, including the use of search engines. Visually-impaired users searching the Web for a specific piece of information took an average of 2.5 times longer than sighted users. The efficiency gap was further quantified by Ivory et al. (Ivory et al., 2004); when blind subjects executed a set of tasks, they took twice as long as sighted users to explore search results and three times as long to explore the corresponding web pages. Leuthold, Bargas-Avila and Opwis (2008), extending the only three non-technical WCAG 1.0 guidelines, defined nine specific guidelines for building enhanced text user interfaces (ETI). The authors demonstrated that the ETI guidelines enhance usability, by evaluating efficiency, errors and user satisfaction of a web user interface developed according to these specific guidelines regarding GUI conformance to standard (WCAG 1.0 guidelines); the study involved 39 blind users who were asked to carry out two tasks (Leuthold et al., 2008).

Considering that the range of different disabilities is so vast and the techniques are quite specific, in the following part of this chapter we limit our discussion to visual impairment, and specifically on the needs of the totally blind, being thoroughly familiar with this field.