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OP2202 > 9. How to: Soft lens fitting > Flashcards

9. How to: Soft lens fitting Flashcards

1
Q

What are the 6 base-line date required for soft CL fit?

A
  1. H&S
  2. Spectacle Rx
  3. Keratometry
  4. Base line measurements: HVID and VPA
  5. Anterior eye examination
  6. Tear film assessment
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2
Q

What is keratometry used for and what is it not useful for?

A

Used as a base-line test to know the curvature of the ocular surface.
Not used: to select a specific lens

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3
Q

Why is corneal staining check done when patient comes in to CL appointments?

A

To ensure no damage was done in the application and remove of Contact lenses

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4
Q

BC is also known as what sometimes?

A

BOZR: Back optic zone radius

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5
Q

What is BC mean?

A

Radius of curvature of the back of the lens

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6
Q

What is meant by TD?

A

Total diameter
This is the overall size of the lens

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7
Q

Sag is determined by?

A

BC and TD

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8
Q

What happens to sag if TD of a lens is altered?

A

Sag is altered

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9
Q

Sag influences what?

A

Lens fit

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10
Q

When fitting patient with soft CL, what is the aim?

A

To achieve optimal fit: a comfortable, well- centered lens and provides a stable vision.

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11
Q

Why are silicone lens stiffer then hydrogels?

A

Silicone lenses have a higher modules.

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12
Q

How do you decide which BC to fit patients with? - 2 methods

A
  1. If 2 different BC available, fit patients with the 2 different BC and let them decide with one is more comfortable- during initial fitting.
  2. Use manufacturers guide to decide which lenses should be used.
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13
Q

How is contact lenses recorded into patient records?

A

Manufacturer & lens name
BC/ TD/ Power

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14
Q

Before fitting lenses in patient, what should you check on the package?

A

Expiry date

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15
Q

3 ways of checking that a lens is the right way round?

A
  1. Check the profile
  2. Crease test
  3. Lens inversion marking
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16
Q

Ideally how long do you let lenses settle before checking its fit?

A

10 minutes

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17
Q

What light is used to check soft lens fit vs RGP lenses?

A

Soft lenses: white light
RGP lenses: Fluorescein

18
Q

9 features used to determine lens fit?

A
  1. Centration
  2. Edge alignment
  3. Coverage
  4. Lag & Sag
  5. Movement on blink
  6. Push- up test
  7. Patient comfort
  8. Vision
  9. What kind of fit the lens gives
19
Q

Centration of lens is seen with what mag?

A

Low mag

20
Q

How is centration of a lens determined?

A

Done in primary position: compare centre of CL to centre of cornea

21
Q

Process of checking centration of a lens?

A

Beam in SL is aligned to to the width one side, once the beam and overlap are aligned. Move the beam to the opposite side and compare to the reference beam.

22
Q

What is good edge alignment in a lens?

A

Edge of the lens should align with conjunctival

23
Q

Steep lens fitting causes?

A

Conjunctival indentation and blanching of vessels

24
Q

Flat fitting lenses may show what when edge alignment is examined?

A

Edge standing

25
Q

What does coverage examine?

A

Does the lens cover the cornea and limbus in all positions of gaze?

26
Q

What beam and brightness is used to examine lens coverage?
What is the procedure to check coverage?

A

Thin beam, bright beam
Procedure: Move slit lamp illumination when patient changes fixation

27
Q

What does lag and sag record?

A

How much the lens resists movement as patient changes fixation.
Lag: Horizontal movement
Sag: Vertical movement

28
Q

Movement of blink assessed at what mag?

A

16X

29
Q

What beam and brightness used to determine movement of blink?
What should the patient gaze at when assessing this?
How is it recorded?

A

Thin and bright beam used
Patient in upgaze - allows to see bottom edge of the lens. Additionally, repeat in primary gaze also. Ask patient to blink and assess the movement.
Recorded in mm

30
Q

Why is movement of blink also assessed in primary position especially for toric lenses?

A

Because toric lenses are thicker at the bottom and can give an artificial movement sometimes

31
Q

What are the different movements seen with Flat lenses compared to steep lens and compared to optimal lenses

A

FLAT LENSES: lenses moves all of the distance: about 1mm
STEEP LENSES: lenses do not move at all: about 0mm
OPTIMAL LENSES: Lenses move by 0.25mm- 0.5mm

32
Q

Mag, beam and illumination used for push-up test?
What target is used for this test?
How is it done?

A

16x
bright beam
thin beam
target: practioners forehead
How it is done: Push the lower lid against the lens gently and release and observe the movement and recovery

33
Q

How is lens comfort identified?
How is lens comfort for steep lens vs optimal lenses vs flat lenses

A

Patient to rate comfort out of 10- ideally should by 8/10 or above
Steep lenses: Good comfort initially, but gets uncomfortable with time
Flat lenses: uncomfortable especially when patient blinks
Optimal: good comfort

34
Q

What are other factors that affect initial lens comfort?

A
  1. Practioner technique
  2. Lens thickness
  3. Lens modulus
  4. Small foreign bodies trapped under the lens
35
Q

How is vision assessed with CL fitting-What is the ideal answer ?

A

Vision should be clear and stable, little difference observed before and after blink.

36
Q

How does blinking affect vision of steep vs flat lenses?

A

Steep lenses: vision improves after blink
Flat lenses: vision worsens after blink

37
Q

3 external factors that affect lens fit

A
  1. Temperature
  2. Humidity
  3. Lens hydration
37
Q

What 2 things are recorded in push-up test?

A
  1. How easy it is to move the lens
  2. How well the lens recovers
38
Q

How to amend a lens with a steep fit?

A
  1. Increase BC.
  2. Try different manufacturer with the same BC.
39
Q

How to amend a lens with a steep fit?

A
  1. Reduce BC.
  2. Try different manufacturer with the same BC.

OP2202 (16 decks)

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