Is there a deficit of early vision in dyslexia?

A majority of dyslexic children have been found in many studies to show a deficiency of early vision, also called transient deficit. A series of four experiments was conducted to test whether or not the performance in different tasks is affected by a transient deficit. However, no clear evidence of a transient deficit was found, although the reliability of the measurements was high and the power of the statistical tests was adequate. All previous findings regarding the transient deficit can be explained by a reduced amplitude of the transient response. The same factor also accounts for a large part of the interindividual variability in this study. The failure to find a transient deficit in dyslexic children is explained only in part by language and preselection, and the outcome challenges the generality of previous findings.