Lecture 12 - Anatomy + Eye Conditions

Question 1

What are the transparent structures of the eye?

Answer 1

Cornea
Aqueous and vitreous humour

Question 2

Wher is the centre of our vision focused onto?

Answer 2

Macula

Question 3

How does light change as it enters the eye?

Answer 3

Changes from being very divergent or be refracted and focused onto the retina

Question 4

What is the condition that presents with a white cloudy lens?

Answer 4

Cataracts

Question 5

Why does a patient with cataracts have blurry vision?

Answer 5

Degradation of lens proteins makes the ens cloudy and white instead of transparent
This leads to the light being scattered in the eye and not refracted/focused properly

Question 6

What structure regulates the amount of light entering the eye?

Answer 6

Pupil

Question 7

Where does most of the refraction of light occur?

Answer 7

Tear film surface of the cornea

Question 8

How can the shape of the eye affect vision?

Answer 8

Different lengths of eyeball lead to the focal point being before or after the retina not on the retina

Question 9

What is an eyeball that’s too long called?

What sight defect does this cause?

Answer 9

Myopic

Short sightedness

Question 10

What is an eyeball that’s too short called?

What sight defect does this cause?

Answer 10

Hypermetropic

Long sightedness

Question 11

Is the light from a closer object more divergent/scattered or focused?

Answer 11

More scattered/divergent

More refraction needed to focus light onto retina

Question 12

What is the reflex called when additional mechanisms are employed to increased refractive capabilities due to the cornea being fixed?

Answer 12

Accommodation reflex

Question 13

What are the 3 things that occurs in the accommodation reflex?

Answer 13

Pupils constrict
Convergence of eye towards middle
Lens gets fatter/thicker

Question 14

What is the purpose of the pupils constricting in the accommodation reflex?

Answer 14

Reduces amount of light entering eye

Question 15

What is the purpose of the convergence of eyes in the accommodation reflex?

Answer 15

Ensures image is focused Ono same area of retina in both eyes

Question 16

What is Presbyopia?

Answer 16

Age related loss of near vision

Question 17

Why does presbyopia occur?

Answer 17

The lens stiffens and become less elastic with age

This means theres a reduced ability to increase refractive capabilities on near objects making it difficult to focus on near objects

Question 18

What are the 2 types of photoreceptor?

Answer 18

Cones
Rods

Question 19

What is the function of Cones?

Answer 19

C in Cones = Colour
Colour vision and high definition at high light levels

Question 20

Where part of the retina are there lots of cones located?

Answer 20

Macula + fovea

Question 21

What is the function of Rods?

Answer 21

Non colour vision
Low acuity at LOW light levels
(Think rods on night vision goggles allow sight at night)

Question 22

Where part of the retina are there lots of rods located?

Answer 22

Peripheral retina (not in macula)

Question 23

How is light converted to action potentials?

Answer 23

Cones/rods detect light
Action potential sent along retinal ganglion cell along axons to the optic disc to the optic nerve
Optic nerve travels to occipital lobe of brain

Question 24

What is visual acuity?

Answer 24

How clear our central vision is

Ability of eye to discern shapes and details

Question 25

How is visual acuity measured?

Answer 25

Snellen chart

Question 26

How does the Snellen chart measure visual acuity?

Answer 26

6m or 20ft from chart
Cover one eye and try and read from big line down to as small as you can go

Lines are numbered with the distance you should be able to read this line at

Question 27

How are the results written for visual acuity?

Answer 27

Always 6 or 20 as numerator (distance away)
Then the line you can clearly read at that 6m distance as denominator

Perfect vision is 6/6 or 20/20

Question 28

Explain what is meant by a visual acuity score of 6/12:

Answer 28

This means at a 6m distance you can only clearly read text that should be perfectly visible form a 12m distance

Question 29

What are the 2 main broad causes of decreased visual acuity?

Answer 29

Transparency issue
Structural issue (refractive problem)

Question 30

What can cause transparency problems?

Answer 30

Cataracts

Question 31

What are some conditions causing reduced refractive ability of structures anterior to retina leading to decreased visual acuity?

Answer 31

Astigmatism (irregular corneal surface)
Presbyopia
Shape of eyeball

Question 32

What other conditions can cause decreased visual acuity?

Answer 32

Retinal detachment
Macular degeneration n
Optic neuritis (inflam of CNII)
Glaucoma

Question 33

What is the red reflex?

Answer 33

Using an ophthalmoscope see if the retina reflects back an orange light =healthy

Question 34

What is a common condition in older adults that would have an absent red reflex?

Answer 34

Cataracts

Question 35

What can an absent red reflex in young children be indicative of which is concerning?

How does the eye look?

Answer 35

Retinoblastoma

Bright white

Question 36

What refractive issues can cause decreased visual acut?

Answer 36

Abnormal corneal surface
Inability of lens to change shape
Size of eyeball

Question 37

What 2 structures have pathologies if decreased visual acuity is caused by a non refractive problem?

Answer 37

Retinal
Or
Optic nerve problem

Question 38

What tool can be used to determine whether a decreased visual acuity is caused be a refractive or non refractive problem?

Answer 38

Pinhole occluded

Question 39

How does a pin hole occluder help determine whether decreased visual acuity is caused by a refractive or non refractive problem?

Answer 39

Pin hole lets only light in that’s perpendicular to cornea and lens (straight line)
This means it doesn’t need to be refracted so it focuses on the macula

Therefore if its a refractive problem the visual acuity should improve with the pin hole

If no improvement then the problem isn’t with refraction (likely optic nerve or retina problem )