Help: Shape of the lens (1 Viewer)

[sneaker]

Hi, can anyone please give me some information about this dot point please?

Analyse information from secondary sources to describe changes in the shape of the eyes lens when focusing on near and far objects

I'm not sure whether the muscles slacken or contract when focussing on the near objects...

thanks

 

[arls]

near objects = fat lens (ciliary body squeezes lens until it is short and dense)
far objects = thin lens (muscles pull the lens into a long thinner shape)
accomodation is the ability of the eye to change its lens shape to focus on objects that are near or far away.

 

[swordfish]

when the eye is looking at distant objects, light reaches the eye in almost parallel rays. This light is focused by the lens in its resting state (on the retina). In this state, the lens is quite flat, the ciliary muscles are relaxed, suspensory ligaments are tightened to keep the lens thin, and the lens is at its lowest strength or refractive power (there is very little bending of light as it passes through the lens).
When the eye is looking at close objects, the light rays tend to diverge as they reach the eye. For proper focusing on the retina to occur, accommodation is necessary. In this state, pupils are reduced in size to exclude the most divergent rays, ciliary muscles contract, causing bulging of the lens (focal length is thus shortened). The lense's refractive power is increased and the image can be focused correctly on the retina.