Question

ACCOMMODATION • Obtain a card with a thin letter on it and bring it towards the right eye with the left eye covered until it becomes slightly blurred. Measure this distance in centimeters and record on Table 6-1. Repeat for the left eye. Table 6-1 Lens Accommodation Data Right Eye Near Point (cm) Left Eye Near Point (cm) What is the reason for the lens to become thicker when looking at a close object? See figure 6-6. 9. What happens to the near point of accommodation distance as a person ages? See figure 6-7. 10. What causes this change in accommodation as age increases?

Answer 1

Answer a the eye lens can & order change its thickness, in to focus light object based coming on from its distance an Looking a closer object, the lens becomes. when thicken this process of change as theckness (hence the in the focal length). hased on the distance of the object viewed get a clear image of it is called accomodation reflex - which is mainly coordinated by the nervous system.. Do A near object appears to be large in the field of vision of the the eye and light from more wides angles are received be the eye. So in order to fixate on a nearby object, the te cilliary muscles contract around the lens to decrease its size. The suspensory ligaments relax and the radial tension around the lens nored This causes the lens to form opherical shape and a higher of refractive power is achieved to age their ability to focus on o bule object unages decreases close up by. a cel is termed This condition pia and the older ones with tion require reading glass for objeet reading nearby obje loss due to the is caused 10 This condition is released. This ca a more spherical ead ing which leads to difficulle geo purposes. This con as Presbyopia and then this condition require real their in the cilliary muscle activity to change the shape of the a ith the change in the object. hence their ability to focus by obiect on close by object decreada decreases in most of of the cases ns. distance, hence

CA There are basically 2 the ones the cause of this that explaine condition and according to the Helmholtz . theory ! the lens as I becomes harder with lag and hence the food muscles cannot change the shape of the lears to focus properly. - According to schachar theory Cons fonds to grow suchthreory, the that de creases the distance between the lears and the cilliary muscles. in which the colliary muscles are ho unable to provide the same ten leas of the for a to the ag edges its shape and hence focus on the nearby objeet decreases. af same tension reers for changing

The eye is a very sensitive organ and is very much controlled by the nervous system because it is a specialized extension of the brain. So,with the help of the nervous coordination it makes appropriate responses for light intensity and object distance to get a distinct and clear image of the object viewed ,to form on the retina.