The human eye, with its various parts, plays a very important role in our lives. It helps us see. This may seem simple enough to just say it like that but a series of operations occur from the point of light rays entering our eyes till we perceive the image of whatever we are seeing. One of these processes is the Power of Accommodation of the eye.
Accommodation of the Eye
The process by which certain muscles (called ciliary muscles) function, to change the focal length of the eyes so that the image is clearly formed on the retina is called the accommodation of the eye. This will vary for near and distant objects and also for objects moving away or towards the eye. By adjusting the focal length, the eye is actually changing its lens power as well, isn’t it? This is called the accommodating power of the eye. Literally. The eye’s power to change its power.
You can actually put this power of your eye to test. Keep your finger in front of you and try to focus only on the finger. You will notice that objects in the background tend to get blurry. Now do the opposite. Keep your finger in front of your face but focus on something in the background. What happens now? Your finger is blurred.
So how does this accommodating power work considering varying distances?
If the object in consideration is at a distance, for the image to form at the retina, the focal length has to be large. Here, the ciliary muscles relax, thereby thinning the eye lens. The focal length increases and the image is formed perfectly on the retina. Similarly, in the case of near lying objects, the ciliary muscles contract and thereby thickening the lens. This causes a reduction in the focal length for ideal image formation.
The Power of accommodation for a person with normal eyesight is around 4 dioptre (unit of lens power).
Did you know that this Power of Accommodation of the eye is limited? The focal length cannot be altered after a certain limit. And why not? Learn all about the accommodating power of the eye with our expert faculty only at BYJU’S.