INVESTIGATION OF ACCOMMODATIVE AND BINOCULAR FUNCTION IN DYSLEXIA

The visual correlates of dyslexia are the subject of controversy, and much evidence suggests that they may include some aspects of binocular and accommodative function. These factors were investigated in 43 con trol and 39 dyslexic children, who were matched for age, sex and perfo rmance intelligence quotient. The dyslexic group exhibited significant ly lower positive and negative vergence reserves, and vergence instabi lity when the eyes were dissociated at near. Their amplitudes of accom modation also were significantly reduced. However, other measures incl uding dissociated and associated heterophoria and accommodative lag an d facility were similar in both groups. The stability of motor ocular dominance, as assessed with a modified Dunlop test, was similar in bot h groups. The results of a simulated reading visual search task sugges ted that the vergence and accommodative dysfunction were not a major c ause of the dyslexia. Further analyses, using reading-age matched grou ps, suggested that these ocular motor correlates were not attributable to the better reading performance in the control group. The most like ly remaining explanation is that they are, in most cases, non-causal c orrelates of the dyslexia.