Question

Test 1: Blind spot determination

1. Take a piece of paper or index card and make an “X” and a large dot about 3 inches apart. Hold it at arm’s length from your face (the X should be on the left, the ● on the right)
2. Close your left eye.
3. Focus your right eye on the “X”
4. Slowly move the card toward your eye until the ● disappears, at this point stop moving the card and hold steady.
5. Measure the distance from the card to your eye. Answer the following questions:

What is the distance?

                        

What is the blind spot?

Test 2: Near point accommodation

We are able to focus (or accommodate) light onto our retina due to the lens. Muscle fibers attached to the lens move it forward and backward within the eye causing the elastic fibers in the lens to stretch and contract. As we age, the elasticity of the lens decreases, and it becomes harder to focus on close objects.

1. Hold a pencil or pen tip at arm’s length in front of one eye. Close your other eye.
2. Slowly move the pin toward your eye, until the pin seems distorted/blurry. At this point, stop moving the pencil or pen.
3. Measure the distance from the pin to your eye. Record the distance:
4. Repeat the same procedure for your other eye. Record the distance:
5. Answer the following questions:

Is the near point accommodation the same for both eyes? Why do you think this is? How would near point accommodation change if you were near-sighted? Far-sighted?

Answer 1

*distance =25cm approximately

*Blind spot-->the portion of retina where optic nerve enters retina is insensitive to light due to absence of both rodes and cones ,this portion is called bl8nd spot.

*for my eyes it is almost same.

*it is due to thr power of accommodation of eyes.here eye changes its focus from a distant site to a near point,it is due to changing the shape of lens.it is done by concentration of ciliary muscle  and relaxation of the zonules that attach the ciliary body to the lens; as a result, the lens thickens and becomes more steeply curved, increasing the refractive power of the eyr and decreases the focal length.

*near sighted-not change

Far sighted-near point is increased.

In near sighted persons he can see near objects so near point dont change. But in far sighted persons he can see far objects clear but not near objects, here he can see near objects at a some distant point than normal point so near point is increased.