Differential Experience-Dependent Plasticity of Form and Motion Mechanisms in Anisometropic Amblyopia

Journal Article


PURPOSE. We measure neural responses associated with form and motion processing in

children with anisometropia before and after treatment with spectacles and occlusion.

METHODS. In this prospective, case-control treatment study, 10 children with anisometropia

and amblyopia and 16 age-matched visually normal children participated. Steady-state visual

evoked potentials (VEP) were recorded from electrodes over the occipital cortex. The visual

stimulus comprised a horizontal bar grating into which Vernier offsets were introduced and

withdrawn periodically at 3.75 Hz. The VEP amplitude at 3.75 Hz (first harmonic [1F]) and 7.5

Hz (second harmonic [2F]) were recorded to index the sensitivity of form/position-sensitive

versus motion/transient-sensitive neural populations, respectively. Response amplitude at 1F

and 2F were recorded over a series of 10 logarithmically spaced offset sizes before and after

treatment. Main outcome measures are VEP amplitude versus displacement functions,

interocular response amplitude differences.

RESULTS. After relaxing into spectacles (minimally-treated state), form/position-sensitive

responses in the dominant/less ametropic eye of the children with anisometropia were larger

and responses in the more ametropic eye were smaller than those of controls. Motiontransient

responses were equal to those of controls in the less ametropic eye, but were

smaller than controls in the more ametropic eye. After treatment, responses did not differ

from those of controls.

CONCLUSIONS. Form and motion responses are differentially susceptible to neural deprivation

via optical blur. Form responses are more plastic than motion responses in minimally-treated

children with anisometropic amblyopia. Most treatment effects occurred above threshold range, suggesting some treatment effects are not detected clinically.


Investigative Opthalmology & Visual Science



Number of Pages


Year of Publication