Optometric Instrumentation 3

Question 1

What is Fundus Imaging

Answer 1

Takes a picture of the retina at the back of the eye

Question 2

Why is fundus imaging useful

Answer 2

For diagnosing certain eye conditions

Question 3

What is meant by fundus

Answer 3

The back portion of the interior of the eyeball

Question 4

What does fundus include

Answer 4

Retina
Blood vessels
Optic disk

Question 5

What colour is fundus

Answer 5

Orange/red background

Question 6

Where does the fundus get its colour from

Answer 6

• Light directly reflected from choroidal blood vessels ( choroid = beneath retina )
• Light reflected from sclera and transmitted through choroidal blood vessels

Question 7

What does amount of light directly reflected from choroidal blood vessels and transmitted through choroidal blood vessels depend on

Answer 7

• Degree of pigmentation of retina

- Degree of pigmentation of choroid

Question 8

What varies from person to person

Answer 8

Retina colour - fundus - back of eye

Question 9

What does degree of pigmentation of retina and choroid depends on

Answer 9

• Age
• Race
• Hereditary
• Metabolic factors

Question 10

What is a Tesselated or Tigroid fundus

Answer 10

• Striation/stripes/ marble effect on background - not blood vessels ( light orange colour )

Question 11

What is the optic disk

Answer 11

Circle in middle
Optic nerve head - photo of back of eye
Optic nerve head comes into back of eye - the face of it = optic disk

Question 12

What does the optic disk vary in

Answer 12

• Colour
• Shape
• Size

Question 13

What are margins

Answer 13

Edge of picture

Question 14

What is meant by cupping of optic disk

Answer 14

Dip in middle of optic disk - isn’t always completely flat.

Question 15

How do you measure cupping and what is it written as

Answer 15

Cup : Disk ( CD ) ratio - shows how much of disk is cupped/dipped
Decimal notation
The vertical diameter of the cup expressed as fraction of vertical diameter of optic disk

Question 16

Is cupping horizontal or vertical direction

Answer 16

Vertical ONLY

Question 17

Normal optic nerve - large or small dip

Answer 17

Small dip
Quite flat optic disk
Same level across

Question 18

Damaged optic nerve - large or small dip

Answer 18

Large dip
Large cup
Deep optic disk

Question 19

Why is it important to measure how much cupping

Answer 19

Size is relevant to certain conditions e.g. glaucoma

If CD ratio changes over years - damage to optic nerve - losing nerve fibres - increases cupping

Question 20

How can you tell where the dip/cup is and how much

Answer 20

• Change of colour - slightly lighter in dip

- Where blood vessels start to kink

Question 21

What to measurements to take for CD ratio

Answer 21

• Vertical height of disc

- Vertical height of the cup

Question 22

What shape is cup

Answer 22

Round

Question 23

What are the two features of Optic Disk

Answer 23

• Choroidal Crescent

- Scleral Crescent

Question 24

What is Choroidal Crescent

Answer 24

• Common form of hyper - pigmentation on edge of disk
• Choroid but not retinal pigment epithelium ( RPE ) extend to optic nerve head - this allows choroid to be visible as a dark region
• Crescent shape on side of optic nerve head ( C shape )
• Layer of pigmentation ( grey colour )

Question 25

What is Scleral Crescent

Answer 25

- Neither RPE nor choroid extend to optic nerve head. - The sclera is visible as a relatively pale region - C shape edge of disk

Question 26

What are the role of blood vessels in eye

Answer 26

Provide the blood supply for inner two thirds of the retina

Question 27

What are the blood vessels in the fundus

Answer 27

The CENTRAL RETINAL ARTERY and the CENTRAL RETINAL VEIN branch from the OPTHALMIC ARTERY and come into the optic nerve head

Question 28

Where do they branch from and to

Answer 28

Each then branches from optic nerve head to serve four main quadrants of retina

Question 29

Difference between arteries and veins

Answer 29

Arteries are smaller Arteries are thin and light - light red = more oxygen Veins are thick and dark

Question 30

What does it mean by crossing over of arteries and veins

Answer 30

Arteries and Veins have crossing points where they overlap

Question 31

The Macula

Answer 31

- Part of eye - fine detailed viewing - Avascular - no blood vessels - Fovea at centre

Question 32

Problems with imaging

Answer 32

- Small pupils - Blinking - Cataracts - misty lens - image hazy

Question 33

What to do if you get a poor view

Answer 33

- Dilate pupils to get large dilated pupil - use eye drops = get more light in = better image

Question 34

What is direct opthalmoscopy

Answer 34

Examining the eye, looking at the external eye, the optic media and the fundus

Question 35

What do you see with an opthalmoscope

Answer 35

- Shine light on pupil with it | - Red reflex - reflection from retina - light bouncing of back of retina

Question 36

How does an opthalmoscope work

Answer 36

- Series of lens - changes = changes focus = clearer view of back of eye - Turn lens down ( power wheel ) - closer to pupil - better image

Question 37

What is direct opthalmoscopy used to diagnose

Answer 37

- Cataract - black strokes - shadows in light - haziness - Diabetes - Hypertension - high blood pressure - change in blood vessels - Retinoblastoma - Macular disease - Optic nerve inflammation

Question 38

What is Optical Coherence Tomography

Answer 38

- Imaging device - Allows you to get image of retinal layers - Cross section through certain section of retina = visualise image of retina

Question 39

How does Optical Coherence Tomography work

Answer 39

- Non - invasive imaging technology - Light directed at target area - Magnitude and relative location of the reflected light is used to produce images - Image based on optical properties of the microstructure of the tissue - Each imaged point generates an axial A - scan - the more A scans - the higher the resolution - As the scanning beam moves across the tissue a cross sectional image is created - B scan - A 3D C scan = collection of tightly packed B scans - Every layer of retina = different properties = reflect different amounts of light back = different shades of grey

Question 40

What is application of OCT

Answer 40

- Useful for certain eye diseases - Relate thickness of retina to disease - Comparison with normative

Question 41

What is Retinoscopy

Answer 41

An objective technique to determine refractive error of the eye ( i.e. myopia, hyperopia, astigmatism)

Question 42

How does retinoscopy work

Answer 42

- Shine light on pupil using series of lenses - Look at reflection of light from fundus on lenses and the way it moves. - Reflection tells us whether light is focused on fundus or not

Question 43

What does retinoscopy allow us to o

Answer 43

What lenses need to correct refractive error

Question 44

What are the advantages of retinoscopy

Answer 44

- Quick - Easy - Reliable/accurate - Subjective - requires minimal co-operation from patient - good for children