Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

clinical skills > Optical instruments 3 > Flashcards

Optical instruments 3 Flashcards

1
Q

What does fundus imaging do?

A

Its a camera which takes a picture of the retina at the back of the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is fundus imaging useful for?

A

diagnosing certain eye conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does a normal eye appear in a fundus image?

A

Orange/red background - which comes from light being directly reflected from choroidal blood vessels and light reflected from sclera and transmitted through choroidal blood vessels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the fundus and what does it include?

A

The back portion of the interior of the eyeball which includes retina, optic disc, vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What determines the amount of light that is directly reflected from the choroidal blood vessels?

A
  • Degree of pigmentation of retina
  • Degree of pigmentation of choroid.
    (varies from eye to eye- variations of normal)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do the degree of pigmentation of the retina and the choroid depend on?

A

Age
Race
Hereditary
Metabolic factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is tesselated or tigroid fundus?

A

the background of the image appaears with a marble affect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the optic disc and how does it vary?

A

optic nerve head

-varies in shape, size and colour and the margins (end of it)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is cupping?

A

optic disc has a dip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is the optic disc measured?

A

In a C:D ratio - the vertical diameter of the cup expressed as a fraction of the vertical diameter of the optic disc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What decimal notation is used for the C:D ratio?

A

goes from 0.1-0.9 being the largest C:D ratio.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the optic disc features?

A

Choroidal crescent

Scleral crescent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is choroidal crescent?

A

c shape hugging the edge of the optic disc
common form of hyper-pigmentation
- choroid (not RPE) extends to the optic nerve head- allowing the choroid to be visible as a dark region.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a scleral crescent?

A
  • Neither RPE or choroid extend to the optic nerve head. The sclera is visible as a relatively pale region.
  • c shape at edge of optic disc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the the blood vessels?

A

central retinal artery
central retinal vein
- they branch from the ophthalmic artery and come into the eye through the optic nerve head.
-Each then branches from the optic nerve head to serve 4 main quadrants of the retina
- provide the blood supply for the inner 2/3rds of the retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does it mean if there is a high C:D ratio?

A

the more cupping there is, the greater risk the eye has of damage (if there has been a change of the C:D ratio size otherwise its normal)

17
Q

How do the arteries and veins appear in the eye?

A 
small diameter arteries
veins are thicker than arteries
arteries light red=more oxygen
Veins are dark red
arteries and veins have crossing points
18
Q

What is another feature of the back of the eye?

A

the macula - area where there are no major blood vessel, at its centre there is a fovea

19
Q

What is the fovea?

A

fine detail viewing
light falls on fovea so you can see detail
avascular zone- doesnt impede vision with no blood vessels

20
Q

What are the problems with imaging?

A

Small pupils- hard to allow light in eye to take image
Cataracts- the misty lens, makes lens hazy
Blinking

21
Q

How to resolve a poor view/image?

A

Eye drops to dilate the pupil (mydriasis)

22
Q

What intrument can examine the back of the eye in more detail than just the fundus imaging?

A

Direct Opthalmoscope- hand held instrument - which examines the back of the eye,/retina looking at the external eye, optic media and the fundus

23
Q

What are the features of the ophthalmoscope?

A

Sight hole
Auxilliary lenses- bunch of different lenses with diff powers
Power Window- different powers of the lens
Power Wheel
Rheostat- light control (make bright or dim)

24
Q

What is a red reflex?

A

reflection from the retina

when you shine light from ophthalmoscope

25
Q

What can you detect from using direct ophthalmoscope?

A

Detect:

  • cataract
  • Retinoblastoma
  • hypertension
  • diabetes
  • macular disease
  • optic nerve inflammation
26
Q

How can you detect cataracts from using an ophthalmoscope?

A

gives you info about the state of the crystalline lens e.g cataract, as the misty lens stops the reflection of the red light, so you get shadows

27
Q

What is OCT?- Optical Coherence Tomography

A

Imaging device which allows to image the retinal lens

28
Q

What does OCT allow you to see?

A

Able to get a cross section of the retina and visualise an image of the retina and see its layers

29
Q

How does the OCT work?

A

-Non-invasive imaging technology
-Infrared light (830nm) directed in patients eye
-The reflection size of the light is picked by the machine and produces an image.
-Image is based on the optical properties of the microstructure of the tissue
-A scan- machine picks up reflections at each image point -
B-scan- as the scanning beam moves across it forms a cross sectional image
- A 3D cube is a collection of tightly packed B-scans

30
Q

What does it mean if there are more A scans?

A

higher resolution of image

31
Q

What is the foveal dip?

A

where light is maximised and hits the photoreceptors to get that fine detail view

32
Q

What else does the OCT do?

A

tells you the thickness of the retina and shows whether treatment works by using numbers.

33
Q

What is retinoscopy?

A
  • An objective technique to determine refractive error of the eye (myopia, hyperopia, astigmatism)
  • shine light (determine rf from the reflections and their sizes) and change lenses
34
Q

What is an advantage of the retinosocopy?

A

quick
easy
accurate
requires minimal co-operation from the patient.

35
Q

What patient is the retinosocopy useful for?

A

Kids- more reliable as its objective

36
Q

Summarise how the retinoscopy works?

A

Shine a light on the pupil
Watch the reflection from the fundus
The reflection tells us whether our light is focused on the fundus or not.
Depending on the direction of the light across the pupil, gives info about what lenses to put infront of the eye.

37
Q

What is RPE?

A

retinal pigment epithelium

clinical skills (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions