Vision 1

Question 1

what is refraction?

Answer 1

Bending of light when it passes from one optical medium to another

Question 2

how does a sharp image form on the retina?

Answer 2

Light waves from an object bend at the cornea, bend some more at the lens to form a clear image on the retina.

Question 3

what is the bending of light waves is called ?

Answer 3

Refraction

Question 4

what occurs to the lens when an object comes closer?

Answer 4

lens becomes thicker & hence more powerful

Question 5

The changes occurring in both eyes as it changes focus from a distant to a close object is called what?

Answer 5

Accommodation

Question 6

what 3 things happen simultaneously & comprise accommodation?

Answer 6

Lens changes shape (becomes thicker & more spherical)
Pupil constricts
Eyes converge

Question 7

how does the lens become thicker?

Answer 7

Ciliary body contraction (parasympathetic)
Suspensory ligaments become lax
Lens is no longer under stretch

Question 8

how do we sharpen our focus?

Answer 8

the pupil constricts to allow only a few rays (those from the object) to pass through

Question 9

what is the muscle that allows pupil to constrict?

Answer 9

Pupillary constrictor (sphincter pupillae)

Question 10

what is convergence?

Answer 10

our eyes have to turn in to look at the object up close

Question 11

what muscle do we use to converge?

Answer 11

medial rectus muscles of both eyes (IIIn of both sides)

Question 12

what is the medical term for short-sightedness?

Answer 12

Myopia

Question 13

what is the medical term for long-sightedness?

Answer 13

Hyperopia

Question 14

what is Astigmatism?

Answer 14

non-spherical curvature of cornea (or lens)

Question 15

what is Presbyopia?

Answer 15

long-sightedness of old age

Question 16

what is emmetropia?

Answer 16

perfect vision

Question 17

desrcibe myopia

Answer 17

Close objects look clear, distant objects appear hazy

light focuses in front of retina

Question 18

what is the most common cause of myopia?

Answer 18

eyeball too long
So the cornea + lens, when they bend rays of light, make the image to form IN FRONT OF the retina. So far off objects not seen clearly.
(Basically “bending power” is too much for eyeball)

Question 19

why can people with myopia still see clearly when objects are close?

Answer 19

“bending power” actually comes into use. The image is formed on the retina without needing to increase curvature of lens.

Question 20

what are symptoms of myopia?

Answer 20

Headaches, Complain of not being able to see blackboard/ distant objects.
Infants & preverbal children- divergent squint
child losing interest in class

Question 21

how do you correct myopia?

Answer 21

Bending power needs to be decreased via biconcave lenses:
Spectacles
Contact lenses
Laser eye surgery

Question 22

describe Hyperopia

Answer 22

Close objects look hazy, distant objects appear clear

light focuses behind retina

Question 23

what is the most common cause of hyperopia?

Answer 23

Eyeball too short or cornea + lens too flat
distant object formed behind retina-accommodative power used to make lens thicker. allowing image to form on retina.
When seeing closer objects, more and more power used until ultimately, lens power is all used up!

Question 24

what are symptoms of hyperopia?

Answer 24

Symptoms of eyestrain after reading etc

Convergent squint in children/ toddlers

Question 25

how do you correct hyperopia?

Answer 25

Biconvex glasses alleviates use of glasses for focussing distant objects and ‘rests’ the accomodative power
Contact lenses
Laser Eye surgery
(correction with glasses/lenses to preserve vision in both eyes and prevent a “lazy eye”)

Question 26

describe astigmatism

Answer 26

Close and distant objects appear hazy

cornea surface has different curvatures in different meridians

Question 27

how does the variance in the two axises affect how the image formed on the retina

Answer 27

bend the light in two different ways so get more than one image

Question 28

how do you correct Astigmatism?

Answer 28

special glasses – called cylindrical glasses (which are curved in only one axis).
Laser eye surgery can also be used to correct the defect.
special contact lenses called toric lenses.

Question 29

describe presbyopia

Answer 29

With age the lens gets less mobile/elastic.
So when the ciliary muscle contracts, it is not as capable as before to change shape.
So seeing near objects starts to become difficult needs glasses to read.

Question 30

what is integrated into cell membrane of rods and cones?

Answer 30

visual pigment rhodopsin in rods and cone opsins S, M and L in cones

Question 31

How does bleaching of the visual pigment result in phototransduction?

Answer 31

Phototransduction cascade

Question 32

What role does Vitamin A play in the visual pigment?

Answer 32

visual pigment regeneration

Question 33

vitamin A deficiency can cause what problem with vision?

Answer 33

nightblindness

Vitamin A is also essential for all healthy epithelium. So conjunctiva and corneal epithelium are also abnormal.

Question 34

what are indications in the eye of vitamin a deficiency?

Answer 34

Bitot’s spots
Corneal ulceration
Corneal melting- which leads to future opacification of the cornea