Page 10 - Cahier-Progressive Lenses-GB.indd

Physiology B Peripheral vision This refers to the visual perception provided by the peri- Perception of movement : 2 phery of the retina. In extra-foveal vision, wearers do not Movement is perceived by the whole of the retina which see objects sharply but locate them in space, perceive is almost uniformly sensitive to motion. Here also, the their form and detect their movement. It occurs princi- variation in prismatic effects plays a role in the wearer’s pally through the peripheral zones of the lens. comfort where it must be slow and smooth across the whole lens to ensure comfortable dynamic vision. Space and form perception: Space and form perception is provided by the retina’s Progressive lenses horizontal and vertical lines thus altering the wearer’s periphery and is directly influenced by the distribution of prism on the progressive lens surface. Depending on the orientation and magnitude of these prismatic effects the power progression introduces slight deformations of visual comfort. Fig. 7 : Perception of form and movement through a progressive lens. 10 Copyright © 2006 ESSILOR ACADEMY EUROPE, 13 rue Moreau, 75012 Paris, France - All rights reserved – Do not copy or distribute.