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Clinical Skills H > slit lamp techniques > Flashcards

slit lamp techniques Flashcards

1
Q

what is tear break up time related to

A

the wetting properties of the tears and the rate of tear production

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2
Q

what is a normal tear break up time

A

> 10 seconds

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3
Q

list 4 types of people that TBUT is reduced in

A
  • elderly
  • xerophthalmia
  • sjogrens syndrome
  • CL wearers
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4
Q

what is instilled in the patient’s eye in order to assess TBUT

A

flourescein, wetted with saline

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5
Q

what must not be used to wet a flourescein paper strip and why

A

tap water, as this can cause pseudomonas

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6
Q

what must be checked on the saline before using it

A

its expiry date

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7
Q

which 2 filters on the slit lamp is used to assess the TBUT

A
  • cobalt blue filter (for the flourescein)

- wratten filter (increases contrast)

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8
Q

list the method of observing TBUT

A
  • focus on the cornea and observe the green tear film
  • ask the patient to take a blink and then stare straight ahead
  • count the number of seconds until you observe dark blue patches appearing on the green tear film
  • when you see this, then stop counting
  • this is your TBUT
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9
Q

what must you focus the slit lamp beam on when assessing TBUT

A

the cornea

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10
Q

when do you stop counting when assessing TBUT

A

when blue patches appear on the green tear film

as this is your TBUT

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11
Q

what is technique for observing the ‘orange peel’ called

A

specular reflection

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12
Q

what is structure is being observed with specular reflection (orange peel)

A

anterior surface of the crystalline lens/corneal endothelium

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13
Q

what magnification should be used with specular reflection

A

high x32-40

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14
Q

what slit beam width should be used with specular reflection

A

2mm paralellopiped

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15
Q

what is the illumination angle with specular reflection

A

angle on incidence = angle of reflection i=r

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16
Q

where is the slit beam focussed with sclerotic scatter

A

on the limbus

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17
Q

how is the light from the slit beam reflected with sclerotic scatter

A

the light is internally reflected within the cornea and re-emerges around the limbus

a halo of light is produced by total internal reflection

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18
Q

which two ways is the eye viewed, with sclerotic scatter

A
  • can be viewed without the microscope
    or
  • if the microscope is to be used, it must be decoupled from the illumination system
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19
Q

which magnification should be used with sclerotic scatter

A

low or naked eye

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20
Q

what slit beam width should be used with sclerotic scatter

A

2mm with parallelepiped

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21
Q

which type of viewing technique is sclerotic scatter

A

indirect

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22
Q

what is the illumination angle for sclerotic scatter

A

decoupled system

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23
Q

where should you focus the slit beam with sclerotic scatter

A

on the cornea

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24
Q

what two pathologies can be picked up with sclerotic scatter

A
  • corneal opacity

- corneal oedema

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25
Q

what does sclerotic scatter check for in the eye

A

the corneal integrity

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26
Q

what are the three types of illumination used in slit lamp

A
  • direct illumination
  • indirect illumination
  • retroillumination
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27
Q

how is direct illumination used

A

the observer looks directly at the structures illuminated by the focussed beam

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28
Q

list all the things which are viewed by direct illumination

A
  • General view /Conjunctiva and fornices
  • Lid margins /Lash follicles /Puncta
  • General cornea /Tear film
  • Limbal vessels
  • Iris detail
  • Lens section
  • Anterior chamber
  • Anterior chamber angle, van Herick
29
Q

how is indirect illumination used

A

the observer looks to the side of the illumination

30
Q

what technique uses indirect illumination

A

sclerotic scatter, to see the conceal integrity

31
Q

how is retroillumination used

A

the observer uses light reflected from a more posterior source to view an object

32
Q

what type of illumination is retroillumination a form of

A

indirect illumination

33
Q

how is retro illumination used to view neovascularisation

A

the observer uses light reflected from the iris or the retina to view the neovascularisation

34
Q

what is diffuse illumination good for

A

giving a good overview of the eye and lids and lashes

35
Q

what 2 things in the lid margin should you look at with diffuse illumination

A
  • punctum

- meibomian glands

36
Q

what should the illumination angle be when using diffuse illumination

A

Swing illumination between 30 deg nasally and 30 deg temporally

37
Q

list the 4 types of optic sections

A
  • corneal section
  • paralellopiped
  • lens section
  • van herick
38
Q

what should be the illumination angle with a corneal section

A

wide of atlas 45 deg

39
Q

what does a greater angle correspond to with a corneal section

A

greater angle = wider optical section

40
Q

how is the corneal section seen as in the slit lamp

A

as a grey arc

41
Q

what can be seen in the arc with a higher mag in corneal section

A

a narrow bright band can be seen on the outer (epithelium) and inner (endothelium) radii of the arc and the dark band between is the stroma

42
Q

what is referred to as a parallelepiped

A

the view of a ‘slice’ of the cornea

43
Q

how do you get a parallelepiped section of the cornea

A
  • obtain a corneal section

- now widen the beam to 1-2mm

44
Q

what is an optical section useful in determining

A

depth of an opacity in the cornea and for examining cataracts

45
Q

what magnification should be used to viewing the lens section

A

low mag

46
Q

how do you obtain a view of the lens in a lens section

A

first focus on the iris and then move across to the centre of the pupil

47
Q

how will the crystalline lens be viewed in a lens section

A

a bright band at the front and back (anterior and posterior cortex) and several lighter bands in the centre, giving it a layered onion like appearance

48
Q

why are you concerned about the angle of the anterior chamber

A

closed angle glaucoma

49
Q

who might be at risk of a closed angle glaucoma

A

elderly and hyperopic patient

50
Q

when can you induce a closed angle attack

A

when you dilate a patient

51
Q

what is van herrick used for

A

to assess the depth of the anterior chamber

52
Q

what mag should be used in van herrick and why

A

low 10x or 16x, to give adequate depth of focus

53
Q

at what angle should the illumination system be to the microscope in van herrick

A

60 deg

54
Q

where should you instruct the patient to look when carrying out van herrick

A

directly at the microscope

55
Q

how do you obtain a view of the anterior chamber with van herrick

A

position a very narrow slit beam on the sclera and move across until you reach the limbus and the beam splits into two

56
Q

what are you assessing the ratio between with van herrick

A

the ratio between the iris and the back surface of the cornea and the thickness of the cornea

57
Q

what ratio of the gap and corneal thickness and grade is a angle which is wide open in van herrick

A

1:1 grade 4

58
Q

what ratio of the gap and corneal thickness and grade is a angle which is open

A

0.5:1 grade 3

59
Q

what ratio of gap and corneal thickness and grade is a angle which is suspicious

A

0.25:1 grade 2

60
Q

what should also be done if an anterior chamber angle which is suspicious ~grade 2 is found in van herrick

A

gonioscopy

61
Q

list 5 reasons that flourescein is used for

A

1) To detect lesions of the corneal epithelium
2) To examine the fit of RIGID contact lenses
3) In applanation tonometry
4) To evaluate the tears (Tear break up time TBUT)
5) To demonstrate the patency of lacrimal drainage

62
Q

what is flourescein angiography and how is it carried out

A

This is a technique used by ophthalmologists to examine the integrity of the retinal vascular system.

It involves injecting 5ml of 10% fluorescein into the brachial vein and then viewing the fundus under UV light. Any leakage of the retinal vessels will be apparent

63
Q

where does purkinje image 1 come from

A

the tear film

64
Q

which purkinje image is the brightest

A

purkinje image 1

65
Q

where does purkinje image 2 come from

A

corneal endothelium

66
Q

which purkinje image is the hardest to see

A

purkinje image 2

67
Q

where does purkinje image 3 come from

A

anterior surface of lens

it is the orange peel effect (i=r)

68
Q

where does purkinje image 4 come from

A

back surface of the lens

Clinical Skills H (18 decks)

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