Lack of spatial remapping of the visual field surrounding a monocular scotoma

Abstract

Background:  Changes in cortical receptive fields following deafferentation raise the question of whether interruption of optic nerve fibres engenders spatial distortion in the region bordering the resulting scotoma.

Methods:  The regularity and uniformity of the spatial metric surrounding a monocular Bjerrum scotoma were studied in both the affected and unaffected eyes of a glaucoma patient, using rigorous psychometric measurements and Amsler grid observations.

Results:  No expansion of distances towards the edge of the scotoma was found; however, such a change occurs at the border of the normal blind spot, though not binocularly and not in the corresponding field of the other eye.

Conclusion:  The findings argue against cortical reorganisation following monocular retinal deafferentation in the adult.

Key words:

• Bjerrum scotoma
• blind spot
• cortical plasticity
• deafferentation
• visual cortex