How Does the Eye Work

'Beauty is in the eye of the beholder...'

As the proverb says, appreciation of beauty is relative and in reality, beauty lies in how we look at things, than how things are. Amongst the instruments of our mind, which bring knowledge to it, an eye is perhaps the most important one. If it wasn't for these amazing instruments that we possess, we would never have been able to appreciate the true beauty of nature and understand where true beauty lies. One wonders how these instruments that enable us to see, work in actuality.

Most of our modern technological innovations consciously or coincidentally mimic phenomena in nature. The study of flight of birds, inspired the first airplane models. Sonar mimics a mechanism by which bats see using sound waves. Similarly, the modern camera mimics the working of the human eye. People may have been inspired by the working of the human eye to build the first cameras. In this article, we will go in reverse mode and understand the working of an eye through analogy of the working of a camera. Of course the eye is far more advanced than a camera, in terms of how it perceives color, depth or three dimensional vision, its adaptive optical mechanism and how brain interprets the image input that it receives. However, at a basic level of functioning, a camera and the eye are inherently similar.

How Do Eyes Work Like Cameras

Let us see how eyes work in a step by step fashion. Let us study the whole process of vision perception, right from the moment light reflected, refracted and emitted by various objects around us, reaches the surface of our eyes. We will track the path of that ray of light, further inside.

Cornea: The Lens Shutter
Cornea is the outermost part of the eye and its working is akin to a lens cover. The cornea is the primary focusing element that focuses diverging light to converge on to the insides of the eye. It is made up of an outer layer of epithelium, whose function is to protect the inner eye. It is made up of transparent regenerating cells, that make the passage of light through it possible. Light is bent when it passes through the cornea and falls on the pupil.

Pupil & Iris: The Aperture Mechanism
Pupil is the central black circle and iris is the concentric colored circle around it, that together constitute the aperture mechanism of the eye. Pupils dilate or contract according to how much light is incident. In low lighted condition, it dilates to gather more light, while in bright light, it contracts to prevent eye damage, from over exposure. Light passes through the pupil and falls on eye lens.

The Eye Lens
The eye lens is the main focusing mechanism, that bends light and makes it fall on the retina of the eye. Sometimes, with age, this lens becomes cloudy and opaque (called a cataract condition) and then needs to be replaced through surgery. The ciliary muscles attached to the eye lens control its curvature and thereby control the focal length of that lens.

Retina: The Photoreceptor or Camera Film
Light bent by the eye lens falls on the retina, which forms the photo receptor mechanism of the eye analogous to the camera film. The retinal nerve cells are some of the most special cells of the human body. They generate electrical signals in response to the light falling on them. The retina contains special cells called 'Rod Cells' that help in perceiving color.

Optic Nerve & Brain: The Image Transport and Processing Mechanism
The electrical signals generated by the retinal nerve cells are then transported towards the optical processing mechanism in the brain called the optic chiasma, by the optic nerve. The point where the optic nerve is connected to the retina doesn't have optic nerve cells. Hence, light falling on this spot is not processed and is called the blind spot! There is one piece of every image that is processed, that is missing in every frame due to the blind spot. Actual real images formed by lenses are always flipped upside down! That means we should also see inverted images through our eye lens. However, that doesn't happen as the image is inverted again by the brain! That is why we don't see it to be inverted.

Hope this article has also renewed the importance of eye care to prevent eye problems and protect this beautiful organ of vision. The aforementioned proverb 'Beauty lies in the eye of the beholder, takes on a whole new meaning, when one perceives this inner beauty of the working of human eye!