Previous reports identified a spatial bias in patients with hemianopia to explain why they tended to bisect a line toward their blind, contralateral visual field. According to them, a perceptual distortion resulting from expansion of the central region of visual space could be involve in their performance. Aims of our study were to confirm the spatial bias in hemianopia with another visuospatial task (the Bells test) and to describe specific pattern of the spatial bias in different visual field impairments. Highlighting specific patterns of performance in the Bells test according to the visual field impairment and link them with a specific spatial bias could be essential in the cognitive rehabilitation of these patients.

Seventy-five patients performed the Bells test. These patients had either a reduction of their visual field from an ophthalmic origin (only one eye, or retinitis; n=5), or a quadranopia (upper left, n=10; upper right, n=10; lower left, n=10; lower right, n=10) or a right hemianopia (n=10) or a left hemianopia without a unilateral spatial neglect (n=10) or a left hemianopia with a unilateral spatial neglect (n=10). We also tested neurologically healthy participants (n=30) matched to age and gender with patients. Two measures were conducted: the Centre of Cancelation (COC) and the probability to miss a bell target according to its spatial localization.

The preliminary results seem to indicate a specific pattern of performance for each group. Patients with both hemianopia and neglect syndrome obtained the poorest performance. Patients with left hemianopia have a spatial bias more important than the spatial bias of patient with a right hemianopia. A surprising result is the one obtained by patients with a lower left quadranopia who exhibited a specific spatial deficit in the right hemi-space.

The main result of this study is to highlight spatial bias with a different magnitude according to the impairment of the visual field. This result has important involvements in the conception and development of cognitive rehabilitation and also in daily life behavior such as driving.