Contrast sensitivity and acuity relationship in strabismic and anisometropic amblyopia

The contrast sensitivity function (CSF) and visual acuity were determined in children and adults with unilateral amblyopia due to strabismus or anisometropia with central fixation. The preschool children were examined repeatedly during occlusion treatment. All amblyopes had CSF deficits. The CSF was characterised by its peak value (the maximal sensitivity, Smax, and the spatial frequency at which Smax occurs, Frmax) calculated by a single peak least-square regression method. The two amblyopic groups showed discrepancies in relationship of both Smax and Frmax versus visual acuity both initially and during treatment. The strabismic cases had a more marked visual acuity deficit in relation to the contrast sensitivity losses, whereas these parameters are affected similarly in anisometropic amblyopes. The relationship between recovery of visual acuity and CSF during the initial month of occlusion treatment was of prognostic significance for the outcome of visual acuity improvement.