A Cultural and Scientific Survey of the Eye and Vision

Gresham College
Course Lectures
  • Fun with Visual Illusions
    William Ayliffe

    Visual illusions entertain and astonish us. How and why they occur is due to the way our visual system processes information. The study of visual illusions leads to many surprising and counterintuitive conclusions about vision. How illusions occur will be illustrated with many beautiful, well-known examples from art history as well as novel images. Following this talk the world out there will seem to be a very different place.

  • Despite sophisticated techniques; Laser, intraocular surgery and contact lenses; spectacles remain the most popular method for correcting optical defects of the eye. Roger Bacon (1266) proposed that convex lenses could be used for elderly people with failing sight, replacing crystals used for magnification. Printing exploded the need for spectacles and by the close of the 20th century amazing advances in surgery corrected vision defects.

  • The transparent tissues of the eye allow light to reach the retina. This highly metabolic tissue requires oxygen delivered by the blood vessels, which are damaged by disease. Diabetic retinopathy is the commonest cause of blindness in the working-age population and in later life hypertension adds to this toll. The eyes maybe the mirror of the soul, but they certainly are a window into our general health. This lecture traces the story from the development of the ophthalmoscope to modern treatments.

  • Fundamentals of Physics, II (PHYS 201) The various postulates of quantum mechanics treated in previous lectures are reviewed and summarized. The uncertainty principle is again discussed and a new one between energy and time is introduced. The quantum mechanical behavior of an electron in a hydrogen atom is described. The principles of quantum mechanics are then generalized to describe two or more quantum particles. It is shown that identical particles have to be bosons or fermions, the latter obeying the Pauli exclusion principle, which in turn is key to explaining the periodic table. 00:00 - Chapter 1. Major Postulates of Quantum Mechanics 20:31 - Chapter 2. Applications of Quantum Mechanics 28:00 - Chapter 3. Energy-time uncertainty principle 41:21 - Chapter 4. Quantum Mechanics of more than one particle Complete course materials are available at the Open Yale Courses website: This course was recorded in Spring 2010.

  • Why We See What We Do
    William Ayliffe

    The visual system has developed to allow us to navigate in a complex and dangerous world in order to find food and to avoid danger. This survival system works by building a complex three-dimensional model based on two-dimensional data from the retina. This model is tested against "reality" and checked with information from other senses and updated if needed. The brain suppresses the complexity of this processing and we believe that vision is instantaneous, real and effortless. But is seeing just an illusion?

  • How Do We See Colour?
    William Ayliffe

    Evolving in a silent, dark world, organisms developed receptors that could detect and differentiate components of the electromagnetic spectrum from the sun. Computation of the proportions of different wavelengths emitted from objects is used to form the perception of colour by the visual system, enhancing the ability to differentiate objects from background. The beauty of colour, used by individuals, artists and commerce is important in all cultures from pre-history to the present.