1. Visual Acuity and Perception of Images Upper Sixth Biology

2. Aims By the end of the lesson you should understand Why the resolution of images can vary How the brain allows the perception of images Aging and vision

3. Visual acuity Sharpness of vision = resolution AKA visual acuity Many rods synapse with a single bipolar cell Information from many rod cells is combined Helps detection of dim light Reduces discrimination of different stimuli

4. Visual acuity cone cells One cone cell, one bipolar cell, one ganglion cell No summation of stimulation Higher visual acuity Cones only in the fovea

5. The brain and perception of images Images we see in our mind are not simple copies Processing of information started at eye, colours, intensities etc

6. Brain and Perception Information is passed to the brain via three pathways Colour Shapes Movement/Special relationships Interconnections, parallel processing Connections with information from other senses and memory

7. Brain and perception-Evolution System appears to have developed to give us the most useful information E.g. Perspective The brain can also ‘fill in’ information

8. Effect of Aging on Vision Cataracts Lens becomes less transparent Proteins coagulate Lens can now be removed Glasses or an artificial lens can be implanted

9. Effect of Aging on Vision Vision become less acute with age Most people lose elasticity of the lens Ciliary body contracts to focus on a close object Suspensory ligaments loosen Lens cannot ‘spring’ into rounder shape May not be able to stretch to see distant objects