The Photodynamics of Vision

Parminder Kaur Mankoo is pursuing PhD in chemistry at Boston University, USA. She worked on the photdynamics of vision for her MSc dissertation at Panjab University. She intends to continue research in theoretical sciences.

Harjinder Singh is a theoretical chemist teaching in Panjab University. His current interests include stochastic processes in physical sciences and application of control theory in molecular processes.

“Lenses, telescopes, and microscopes are man-made optical gadgets designed to help the human eye see very distant or very small objects. But the eye itself is an optical instrument designed by Mother Nature, the most ingenious of all designers, and it still remains the most versatile optical instrument ever made.”

George Gamow & J M Cleaveland 
Physics: Foundations and Frontiers 
Prentice-Hall, New Delhi, 1963

Vision is one of our primary senses. It is the ability to identify, process and interpret what is seen by the eye. It is a powerful mechanism for parallel processing of information received at the speed of light from near and remote scenes. The volume of information received by vision is certainly more than that received by our other senses. Our eyes try to see clearly the objects in our surroundings at variable distances and under various intensities of light, which is achieved by a very complex arrangement of molecular structures in the eye. We perceive objects when an image is formed on the retina, situated towards the back of the eye working as a photographic film in a camera after which a signal is sent from there to our brain through the optic nerve. The retina is much more advanced than a photographic film because it can automatically change its sensitivity depending upon the amount of illumination present. In a normal eye (Figure 1), the rays of light coming from a distant object get focused by the cornea and lens of the eye into the retina and form a sharp image.

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Address for Correspondence
J Srinivasan 
Chairman, Centre for Atmospheric & Oceanic Sciences 
Indian Institute of Science 
Bangalore 560 012, India. 
Email: jayes@caos.iisc.ernet.in