deficit theory also have concerns about two certain types of group (e.g., Wolf, 1991;

Wolf & Bowers, 1999). Actually their research findings (Wolf & Bowers, 1999) suggest

that there are three types of RD based on processing deficits: a group of children with

mostly a phonological processing deficit, a group who have mostly a naming deficit, and

a group who have both phonological and rapid-naming deficits. Obviously, the last two

groups of children who have a rapid-naming deficit would not be well served if early

intervention programs that are mainly based on phonological awareness skills were

provided. In sum, although a growing body of research supports the importance of rapid-

naming skills as a separate indicator from phonological awareness of RD, it is still

inconclusive. Hence, there is a need to replicate such studies to clarify this issue.

Problems with Prior Research

 While phonological awareness has captured researchers' attention, reading-related

vision studies have received less attention. As a result, there has been a lack of research,

particularly in the field of education. Specifically, only a few correlation studies

involving both visual skills and verbal skills in the regression models have been

undertaken (e.g., Eden et al., 1993, 1995). Moreover, a lack of research has revealed

inconsistent results. To illustrate, while McKinney, Short, and Feagans (1985) reported

that only 7% of a sample with learning disabilities showed severe visual problems,

Watson (1990) reported that 52% of a sample of students with reading disabilities

exhibited some type of visual processing problems. In addition to inconsistency, the

findings were conflicting and yielded mixed outcomes. For example, some researchers

were able to indicate a significant difference in the visual abilities between poor readers

and nondisabled readers (e.g., Watson, 1990). In contrast, others found no such

differences between the two groups (e.g., Vellutino, 1987).