1. PP, Corneal & lens section

Question 1

What makes slit lamp better than direct ophthalmoscopy?

Answer 1

1.Better working distance
2. Observer more comfortable
3. Patient held steady
4.Brighter beam
5. Bigger FOV
6. Stereoscopic (depth perception)
7. Fine controls
8. More ways of manipulating the beam
9. More filters
10. More magnification

Question 2

How does slit lamp have more magnification?

Answer 2

Replaces plus lens mag with a microscope

Question 3

How does slit lamp have a brighter beam?

Answer 3

Sharp focus projector illumination system

Question 4

How does the slit lamp have more ways of manipulating the beam?

Answer 4

The common pivot allows for more manipulation

Question 5

How does the slit lamp allow stereoscopic depth perception?

Answer 5

Binocular eyepieces

Question 6

How does the slit lamp allow for px to be steady and observer be comfortable?

Answer 6

Patient is seated with head and chin rest, and the observer is also seated

Question 7

How does the slit lamp allow for fine controls?

Answer 7

By the use of the joystick

Question 8

How does the slit lamp make working distance better?

Answer 8

The microscope allows for greater working distance

Question 9

What trade offs (disadvantages) do you get with high magnification?

Answer 9

Smaller FOV and depth of focus

Question 10

What trade offs (disadvantages) do you get with high resolution?

Answer 10

Smaller depth of focus

Question 11

What trade offs (disadvantages) do you get with brighter slit?

Answer 11

Less patient comfort and more glare and scatter

Question 12

What trade offs (disadvantages) do you get with thinner slit?

Answer 12

Smaller area viewed

Question 13

Draw the common pivot

Question 14

What are the ways of increasing resolution of slit lamp? And what are the drawbacks?

Answer 14

1. Increase the diameter of the objective front lens ( increased aberrations at edges. Decreases depth of focus)
2. Use a medium like jelly between the eye and front lens (impractical)
3. Decrease working distance (reduces Px comfort)
4. Use short wavelength of light (blue)(colour rendering would be affected)
5. Reduce aberrations by creating advanced lens system (expensive)

Question 15

Draw a diagram of parallelpiped

Question 16

What are the advantages of parallelpiped?

Answer 16

1. Scans both epithelium and endothelium of cornea
2. Quick and effective to screen for problems especially from contact lens aftercares
3. Mag is high enough to detect small lesions

Question 17

What are the disadvantages of parallelpiped?

Answer 17

1. Difficult to perform due to curvature of cornea and varying thickness of cornea
2. Doesn’t give info on the depth of lesions

Question 18

Name layers of cornea and their thicknesses

Answer 18

Epithelium 40-50 micrometers
Bowman’s 8-15 micrometers
Stroma 470-500 micrometers
Descemet’s 10-12 micrometers
Endothelium 4-6 micrometers

Question 19

What are the advantages for corneal section?

Answer 19

1. Extremely detailed look at layers of cornea
2. Can judge the depth of anomalies

Question 20

What are the disadvantages to corneal section? And what to do instead?

Answer 20

Poor scanning for trying to find the lesions -
so instead use PP to find the lesion and investigate with corneal section.

Question 21

Draw a diagram for corneal section

Question 22

Draw a diagram for lens section

Question 23

what is the meaning of empty magnification?

Answer 23

the magnification can go higher and higher but the resolution doesn’t get any better so image is blurred. Resolution is more important

Question 24

Why do we need good colour rendering?

Answer 24

So we can see small features such as cells in the anterior chamber

Question 25

Sometimes from lashes can look like scratches on the cornea, how could we check this?

Answer 25

Ask Px to blink

Question 26

What is specular reflection from corneal endothelium for and why?

Answer 26

To check any changes in endothelial cells. Any polymorphism or polymegathism. We need to check because we are born with our endothelial cells which don't get replaced. The endothelial cells are important to prevent corneal swelling and to maintain transparency of the cornea.

Question 27

Who is specular reflection from corneal endothelium useful for mostly?

Answer 27

To check in those who've just had cataract surgery and CL aftercares.

Question 28

Why do we want to use the iris as the diffuse reflector in retro illumination of the iris?

Answer 28

It allows us to look in detail at low contrast features which would otherwise be lost in the glare of direct.

Question 29

What is used for grading cataracts?

Answer 29

The LOCS III grading system

Question 30

Which type of cataracts does retro illumination off the fundus grade?

Answer 30

Cortical and Posterior subcapsular / posterior capsular cataracts. Not Nuclear

Question 31

What are the infammatory signs in the aqueous when using conical beam?

Answer 31

WBC (leukocytes) look like dust because they are bigger Proteins (Interleukin and Fibrinogen) look like smoke because they are smaller so look like haze

Question 32

What is the smoke/ haze due to proteins in conical beam also known as?

Answer 32

Tyndall's effect / Protein flare

Question 33

Why is it better to start conical beam on the iris rather than on the skin?

Answer 33

So we can check for Hypopyon (WBC accumulation (Pus) or Hyphaema (Blood) at the bottom of anterior chamber

Question 34

What is the principle of sclerotic scatter?

Answer 34

Total internal reflection to check for corneal opacities.

Question 35

Which technique is used to estimate anterior chamber depth / angle?

Answer 35

Van Herick's

Question 36

The front of the eye is cold and the back of the eye is warm, what does this cause?

Answer 36

A convection current of aqueous humour.

Question 37

What would a lesion in sclerotic scatter look like?

Answer 37

Some leakage of light

Question 38

How do you know you are perpendicular to Px's cornea as we don't know the curvature in Van Herick's ?

Answer 38

Van Herick chose to put illumination system at a arbitrary angle 60 degs.