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Clinical Skills > Optometric Instrumentation 3 > Flashcards

Optometric Instrumentation 3 Flashcards

1
Q

What is Fundus Imaging

A

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

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2
Q

Why is fundus imaging useful

A

For diagnosing certain eye conditions

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3
Q

What is meant by fundus

A

The back portion of the interior of the eyeball

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4
Q

What does fundus include

A

Retina
Blood vessels
Optic disk

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5
Q

What colour is fundus

A

Orange/red background

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6
Q

Where does the fundus get its colour from

A
  • Light directly reflected from choroidal blood vessels ( choroid = beneath retina )
  • Light reflected from sclera and transmitted through choroidal blood vessels
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7
Q

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

A
  • Degree of pigmentation of retina

- Degree of pigmentation of choroid

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8
Q

What varies from person to person

A

Retina colour - fundus - back of eye

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9
Q

What does degree of pigmentation of retina and choroid depends on

A
  • Age
  • Race
  • Hereditary
  • Metabolic factors
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10
Q

What is a Tesselated or Tigroid fundus

A
  • Striation/stripes/ marble effect on background - not blood vessels ( light orange colour )
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11
Q

What is the optic disk

A

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

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12
Q

What does the optic disk vary in

A
  • Colour
  • Shape
  • Size
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13
Q

What are margins

A

Edge of picture

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14
Q

What is meant by cupping of optic disk

A

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

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15
Q

How do you measure cupping and what is it written as

A

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

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16
Q

Is cupping horizontal or vertical direction

A

Vertical ONLY

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17
Q

Normal optic nerve - large or small dip

A

Small dip
Quite flat optic disk
Same level across

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18
Q

Damaged optic nerve - large or small dip

A

Large dip
Large cup
Deep optic disk

19
Q

Why is it important to measure how much cupping

A

Size is relevant to certain conditions e.g. glaucoma

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

20
Q

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

A
  • Change of colour - slightly lighter in dip

- Where blood vessels start to kink

21
Q

What to measurements to take for CD ratio

A
  • Vertical height of disc

- Vertical height of the cup

22
Q

What shape is cup

A

Round

23
Q

What are the two features of Optic Disk

A
  • Choroidal Crescent

- Scleral Crescent

24
Q

What is Choroidal Crescent

A
  • 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 )
25
Q

What is Scleral Crescent

A
  • Neither RPE nor choroid extend to optic nerve head.
  • The sclera is visible as a relatively pale region
  • C shape edge of disk
26
Q

What are the role of blood vessels in eye

A

Provide the blood supply for inner two thirds of the retina

27
Q

What are the blood vessels in the fundus

A

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

28
Q

Where do they branch from and to

A

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

29
Q

Difference between arteries and veins

A

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

30
Q

What does it mean by crossing over of arteries and veins

A

Arteries and Veins have crossing points where they overlap

31
Q

The Macula

A
  • Part of eye - fine detailed viewing
  • Avascular - no blood vessels
  • Fovea at centre
32
Q

Problems with imaging

A
  • Small pupils
  • Blinking
  • Cataracts - misty lens - image hazy
33
Q

What to do if you get a poor view

A
  • Dilate pupils to get large dilated pupil - use eye drops = get more light in = better image
34
Q

What is direct opthalmoscopy

A

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

35
Q

What do you see with an opthalmoscope

A
  • Shine light on pupil with it

- Red reflex - reflection from retina - light bouncing of back of retina

36
Q

How does an opthalmoscope work

A
  • Series of lens - changes = changes focus = clearer view of back of eye
  • Turn lens down ( power wheel ) - closer to pupil - better image
37
Q

What is direct opthalmoscopy used to diagnose

A
  • Cataract - black strokes - shadows in light - haziness
  • Diabetes
  • Hypertension - high blood pressure - change in blood vessels
  • Retinoblastoma
  • Macular disease
  • Optic nerve inflammation
38
Q

What is Optical Coherence Tomography

A
  • Imaging device
  • Allows you to get image of retinal layers
  • Cross section through certain section of retina = visualise image of retina
39
Q

How does Optical Coherence Tomography work

A
  • 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
40
Q

What is application of OCT

A
  • Useful for certain eye diseases
  • Relate thickness of retina to disease
  • Comparison with normative
41
Q

What is Retinoscopy

A

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

42
Q

How does retinoscopy work

A
  • 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
43
Q

What does retinoscopy allow us to o

A

What lenses need to correct refractive error

44
Q

What are the advantages of retinoscopy

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

Clinical Skills (6 decks)

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