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Conjugacy of saccades in deep amblyopia
G F Maxwell1, H G Lemij, H Collewijn
1Department of Physiology, Erasmus University, Rotterdam, The Netherlands.
Purpose:
To determine the degree of conjugacy of saccades in humans with one deeply amblyopic eye, to assess whether Hering's law requires good binocular visual acuity.
Methods:
By means of magnetic search coils, horizontal saccades were recorded accurately in 11 subjects with unilateral, deep amblyopia. The recordings were compared to those made in 11 normal subjects. In addition, three subjects with amblyopia were submitted to artificial anisometropia, which called for nonconjugate adaptation of their saccades.
Results:
The saccades of most subjects with amblyopia were nonconjugate. These nonconjugacies often were larger in one direction than in the opposite one. The magnitude of the nonconjugacies varied inconsistently with the size of the saccades. In addition, the amblyopic eye often showed conspicuous drift. The saccades adapted nonconjugately to the imposed anisometropia.
Conclusions:
In deep amblyopia, the two eyes often make saccades that are unequal in size. The amblyopic eye does not move aimlessly, roughly following the movements of the normal fellow eye. Instead, the saccades of the amblyopic eye appear to reflect a deliberate oculomotor strategy, bringing visual targets to presumed retinal points of preference.