Validity Reassessment of Developmental Eye Movement (DEM) Test in the Italian Population

Background. This study confirms and expands the original DEM validity data initially published, but for the Italian population. We not only use the same measures as in the original study, but also new methods of psychometric and statistical analyses as well. Methods: Four experimental groups of children, a total of 152 subjects, were evaluated with the DEM test and various other psycho-educational tests to assess DEM validity. Results: The results confirm the suitability of the four types of validity given in the DEM manual in the Italian population. Moreover, by using a construct validity scheme, the results show: a significant developmental trend for all variables (p<0.001), a significant internal correlation (p<0.01), a correlation with reading tests (p<0.05), a significant difference in vertical time (p<0.005) and adjusted horizontal time (p<0.05) in a group of LD children. The results also show a convergence validity with a test of visual exploration (p< 0.01), but a divergence validity with subjective evaluation of ocular movements, and the factorial analysis accurately demonstrates saturation to three main factors. Conclusions: These more extensive analyses confirm the validity of the DEM test to assess ocular motility in the developmental age in the Italian population and permits differentiation of ocular motility and naming problems. The confirmation of validity has created a more appropriate baseline for a future standardization of the DEM test in the Italian population.