Optics of the Eye

This chapter shows how the human eye is a wonderful instrument and how it functions. The chapter provides brief introduction of the diaphragm and the lens. Kepler was the first who discovered that the image is formed on the retina. He had also suggested that the inverted image appeared on the retina. Mariotte had found the Mariotte spot or blind spot. The concept of myopia and the Snellen notation are also explained. The chapter talks about photoreceptors, visual pigments and the phosphorescent effect in the eyes of animals like cats. This is created by the tapetum, an important structure of the eye that improves the night vision of terrestrial animals. Further it describes compound eyes that are constituted of ommatidia and how these ommatidia help insects see polarized light and to know the direction of the sun although they cannot see the sun.