Abstract

The optics of the human eye have been studied by learned men for many centuries, one of which was Ibn al-Haytham (known in the West as Alhazen), the most influential figure in the study of optics and vision in the Middle Ages (Alhazen and Sabra 1989). Although eyeglasses were introduced in the thirteenth century, it was not until the seventeenth century that Johannes Kepler formulated an accurate theory and the correction of myopia (positive defocus or nearsightedness) and hyperopia (negative defocus or farsightedness). Two centuries later, George Airy devised a cylindrical lens for the correction of astigmatism (Airy 1827; Levene 1966).