Topographical patterns of visual field recovery: Changes of objective and subjective visual field size in brain-lesioned patients

Abstract

 

We observed topographical patterns of functional recovery over sixmonths of visual restitution training, comparing changes of objective and subjective visual field size. Perimetric and campimetric tests served as objective measures of intact visual field size. The subjective position of the visual field border was indicated in a standardized chart of the right and left eye. After baseline testing, nineteen patients with post-genicular lesions of the visual system performed visual restitution training. Diagnostic procedures were repeated after six months of treatment. Correlations between objective and subjective visual field size and changes in both variables over the treatment period were determined. Topographical patterns of visual field recovery in both tests were analyzed. Even before training, subjective visual field size was substantially correlated with perimetric measurements. In parallel with an increase of stimulus detection in “objective” visual field tests, a decrease of subjective defect size was observed (significant for the left eye) during the treatment period, and correlations of subjective and objective visual field size increased. Form and size of the scotoma were adequately represented in most patients, with foveal defects being perceived as larger than more peripheral parts of the scotoma. Training-induced improvement could also be recognized in patients' drawings. Visual restitution training increases intact visual field size in “objective” visual field tests but also affects the subjective representation of the defect. Objective as well as subjective measures of scotoma size reflect the architecture of the visual system because topographical patterns of recovery follow the laws of the cortical magnification factor and the subjective importance of improvement depends on the eccentricity of the border shift.