Homeostais - how the eye focuses

Question 1

what is the cornea?

Answer 1

a fixed focus

Question 2

what is the lens surrounded by?

Answer 2

ciliary muscles (circular) connected by fibres (sensory ligaments)

Question 3

what do the ciliary muscles and suspension ligaments have control over?

Answer 3

by contracting or relaxing, they can change the thickness of the lens

Question 4

how does the eye focus on distant objects?

Answer 4

the light from distant objects only needs to be focused a relatively small amount so the ciliary muscles relax and the suspension ligaments are pulled tight. the lens becomes thin and light rays only slightly refract

Question 5

how does the eye focus on near objects?

Answer 5

light from near objects need to be focused a large amount so the ciliary muscles contract and the suspension ligaments are loosened. the lens becomes thicker and light is refracted strongly

Question 6

when do light rays not focus correctly on the retina?

Answer 6

if people are short sighted or long sighted

Question 7

what is long sighted known as? what does it mean?

Answer 7

known as hyperopia where the eye can’t focus on near objects due to the eyeball being too short. the light is focused behind the retina or the lens can become thicker (in old people)

Question 8

how is long sightedness treated?

Answer 8

with convex lens glasses that partially focus light before entering the eye

Question 9

what is short sightedness known as? what is it?

Answer 9

myopia which is where the eye cant focus on distant objects due to the eyeball being too long so light focus infront if the retina. this could be due to the lens getting too thick

Question 10

how is short sightedness treated?

Answer 10

with concave lens glasses that partially unfocused the light before entering the eye

Question 11

what are the other options for treating short or long sightedness?

Answer 11

• contact lenses that sit on the eyeball and refract light
• laser surgery to change the shape of the cornea
• artificial lens