Accommodation of the eye is the process where certain muscles, the ciliary muscles, function to change the focal length of the eye. It is responsible for the formation of clear images on the retina. It can vary for the objects which are near or distant. The power of the lens is changed by changing the focal length.Â
What is the power of accommodation of an eye?
Our Eye has a lens to focus the image(light from objects) onto the screen(retina). The muscles around the eye try to change the focal length of the eye so that the image is correctly focused on the retina, which is then picked up by the brain. This process of changing the power of the lens(by changing the focal length) is called the power of accommodation of the eye. When the muscles become weak or are not able to change the focal length then we experience difficulties in seeing objects clearly.
When an object is kept at a far away distance, the focal length should become large for the image to form in the retina. The ciliary muscles relax by thinning the lens of the eye. When the focal length increases, the image is formed perfectly on the retina.
In the case of a nearby object, the ciliary muscles contract, and the lens will get thick. This leads the focal length to reduce for the ideal image formation. The power of accommodation of the eye vas got limits as the focal length cannot be increased after a certain limit.
What is the power of accommodation of the eye of a normal person:
The power of accommodation of a person’s normal eyesight is 4 Dioptre.
Dioptre is the unit of power of a lens. The power of the lens is equivalent to the reciprocal of focal length (f). It is denoted as D and its focal length is 1m.Â
The optical power for a healthy eye is about 40 D, which means that the ability to focus on an object is 1/40 of a meter from the eye. A young human eye can change the focus from infinity to the nearest point (6.5cm) from the eye.
This change is due to the reduction in zonular tension which is induced by ciliary muscle contraction. The amplitude of accommodation declines with an increase in age.
Contact lenses are used to assess the health of an eye, which helps eye care professionals to check for any myopia, hyperopia, or astigmatism.
Research Articles on the power of accommodation of the eye
In this article titled “Accommodative response in various design soft contact lens wearers; pp. 333–340,” the authors discuss the global research challenges regarding the progression of myopia in young people due to the poor accommodation of the eye. Here in this article, the authors assess the accommodative lag using various designs of multifocal contact lenses at different working distances.
In this article, the authors discuss the relationship between aging and the accommodation of the eye. Aging reduces the ability of the lens to change shape, and to adjust for close or distant vision. [Link:https://www.ijars.net/articles/PDF/2534/42104_CE_PD(SHU)_V.2(AsG_OM)_CE[Ra1]_F(SHU)_PF1(AG_SHU)_PFA(SHU)_PB(AG_SHU)_PN(SHU).pdf]
