CONCORDANCE OF SMOOTH-PURSUIT AND SACCADIC MEASURES IN NORMAL MONOZYGOTIC TWIN PAIRS

Although the range of normal ocular motor performance is broad little is known about the sources of variability Generic transmission of eye movement deficits has been described but such possible control of norm al function has been little investigated Characteristics of smooth pur suit and saccades can be examined for the degree of concordance in rel ated individuals. In this pilot study, we studied saccades and pursuit in eight monozygotic (MZ) twin pairs. The statistical analysis of the data used the intraclass correlation of MZ twins (rMZ) to estimate wh at fraction the covariance of the twin pairs was of the population var iance. All saccadic measures showed significant MZ correlations (p < 0 .05). Smooth pursuit gains were even more highly correlated (p < 0.001 ). These results indicate considerable similarity within pairs of twin s, particularly for horizontal smooth pursuit, and suggest that larger studies on monozygotic and dizygotic twins would be desirable, to hel p separate out the relative contributions of environmental and genetic factors.