Fixation instability and vergence instability during binocular viewing can interfere with ocular motor development, according to a study recently published in Experimental Eye Research.

The Dallas-based investigators found both amblyopic and nonamblyopic children treated for anisometropia, strabismus or both had larger fixation instability and vergence instability than controls. They also reported that amblyopia actually worsens the non-preferred eye, adding to its instability.

The study looked at 160 children between the ages of four and 12. Of that 160, 98 were amblyopic and 62 were nonamblyopic. They were weighed against 46 age-similar controls. The subjects’ fixation stability was measured with binocular fixation of a 0.3 degree diameter dot for 20 seconds using a 500Hz remote video binocular eye tracker.

The doctors also captured the subjects’ best-corrected visual acuity, Randot Preschool Stereoacuity and extent of suppression scotoma.