Document Type

Thesis

Degree

Master of Science

Major

Vision Science

Date of Defense

4-19-2013

Graduate Advisor

Carl J Bassi, PhD

Co-Advisor

Franzel, Aaron Stephen

Committee

Carl J. Bassi, PhD

Aaron S. Franzel, O.D.

Ralph P. Garzia, O.D.

Abstract

Objective: Early visual processing integrity is correlated with word reading. In previous reports, duration of fixation when reading sight-words has been established as an early sensory correlate of single word decoding ability. In attempts to model the direct and indirect predictive value between duration of fixation, number of fixations, orthographic processing, phonological processing, and rapid automatized naming (RAN) to word decoding ability, we compared Visagraph duration of fixation and number of fixations data to results of the Processing and Learning Test-Reading and Writing (PAL-RW) and dyslexia screening test (DST) in a structural equation modeling (SEM) analysis. Methods: Seventy-four students with reading difficulties (age range 8-13) referred to the Pupil Project were used in the analyses. A theoretical model outlining the proposed relationship between factors was established, then direct and indirect effects between factors were calculated in multiple regression analysis. Model fit was evaluated with SEM analyses in Amos. Results: Of the five factors explored (duration of fixation, number of fixations, RAN, orthographic and phonological processing), only number of fixations and phonological processing failed to hold a significant (p<0.05) direct effect on word reading. RAN and duration of fixation held significant indirect effects mediated through orthographic processes. The model was strongest when all five factors were incorporated. In all models, RAN, duration of fixation, and orthographic processing held the strongest relationship to word reading. Conclusions: These results suggest that, at least for our clinical population with visually related reading difficulties, RAN, duration of fixation, and orthographic processing held higher path coefficients than phonological processing or number of fixations in predicting single word reading ability. Further, RAN was a good predictor for orthographic processing. Duration of fixation held the second strongest predictive value of any single factor to word reading. It may serve optometrist well in analyzing risk factors for dyslexia. Results suggest modification to the double deficit hypothesis for dyslexia to incorporate visual/orthographic processing.

Share

COinS