Brainscape's Knowledge GenomeTM

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


See full index

OPTOM 430 Test > Exam prep > Flashcards

Exam prep Flashcards

1
Q

Problems with loose fitting lenses? (5)

A
  • lens decentration
  • lens awareness
  • fluctuating vision
  • dislodged lenses
  • lens popping off eye
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Problems with tight fitting lenses? (6)

A
  • lens binding
  • poor tear exchange
  • limbal redness
  • lens indentation
  • corneal dessication/staining around lens
  • lens getting stuck inferiorly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Problems with spherical RGP on highly astigmatic corneas? (5)

A
  • compromised fitting relationship in one or both meridians
  • corneal warpage
  • spectacle blur
  • inconsistent fitting dynamics
  • corneal staining in tight areas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Bennet’s design tricurve and quadcurve

A

Tricurve:
SCR: add 1.0-1.5mm to BC/0.3mm wide
PCR: add 1.5-2.0 to BC/0.4mm wide

Quadcurve:
SCR: add 0.8mm to BC/0.3mm wide
ICR: add 1.0mm to BC/0.2mm wide
PCR: add 1.4 to BC/0.2mm wide

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

A change in radius of ___mm results in ___D of change

A
  1. 1mm

0. 50D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Symptoms of ghosting, flare or diplopia can be due to what?

A

pupil not being fully covered by optic zone

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

What are characteristics of a lens that is too small (3)

A
  • move freely on eye/decentre easily
  • dislodge/pop off eye with quick lateral gazes
  • looser fitting due to shorter sag height
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are characteristics of a lens that is too big? (4)

A
  • excessive lens tightness
  • restrict movement
  • limit tear exchange
  • may irritate limbal area –> tearing and lens awareness
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Large lenses can be particularly problematic when associated with?

A

high Rx due to thick centre or edges

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

What are the typical TD/OZ combinations?

A

<9.00mm (7.0)
9.0-9.3mm (7.5)
9.5-9.8mm (8.0)
>9.8mm (8.5)

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

To counteract the BC becoming steeper when increasing TD, what should happen to the BC for every 0.5mm increase in TD?

A

BC should be made 0.05mm flatter (0.25D)

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

increasing/decreasing TD makes the lens steeper/flatter causing changes in power. What rule is used to help counteract this?

A

SAM FAP

steeper add minus, flatter add plus

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

increasing/decreasing TD also has an effect on what other fitting characteristic?

A

edge lift
increasing TD = increase edge lift
decreasing TD = decrease edge lift

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

Summarise the effects of a large lens (5)

A
  • fit more tightly
  • move less
  • can have higher edge lift
  • can have more lid attachment
    generally more stable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Summarise the effects of a small lens

A
  • fit more loosely
  • move more
  • can have lower edge lift
  • can have less lid attachment
    generally less restrictive to tear flow and oxygenation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What parameter has the most influential change on edge lift?

A

changing SCR

17
Q

ideal edge lift width?

A

0.3-0.5mm

18
Q

How can you modify a high plus power RGP to counter inferior decentration?

A

add minus carrier on edge

19
Q

how can you modify a high minus power RGP to counter lid interaction problems?

A

add plus lenticular –> wedge shape

20
Q

Why is PMMA a good material to use as a trial lens? (3)

A
  • scratch resistant and machineable

- has no surface charge

21
Q

When would you consider a lower Dk RGP material? (2)

A
  • to reduce surface deposits

- to reduce flexure

22
Q

Dimple veiling etiology, signs and management

A

etiology: gas bubbles trapped in a large post-lens tear film caused by lens being too steep centrally and/or too much edge lift peripherally. Bubbles act like solids and cause pits in the epithelium.
- pool with NaFl
- if significant can cause irregular corneal topography
- decrease vision when located centrally

Mx:
reduce post-lens tear film clearance by reducing sagittal height (if central) or reduce edge lift if source of bubbles from high peripheral tear reservoir

23
Q

Corneal warpage etiology, signs, symptoms, management

A

etiology:
- mostly mechanical
- associated underlying cause is prolonged oedema
- ill-fitting lens

signs:
- corneal topographic shape change
- distorted keratometry mires
- irregular retinoscopy results
- indecisive subjective refraction
- reduced BCVA in spectacles
- spectacle blur

symptoms:

  • usually asymptomatic as surface irregularity usually masked by CL
  • long hours of CL wear

Mx:
Corneal rehabilitation
- change to lenses with increased Dk/t and cease CL wear
- repeat refraction and topography 1-2 weekly until changes stabilise
- withdrawal of original lenses and final refitting

24
Q

Peripheral corneal staining (3 and 9 o’clock) etiology, signs, symptoms, Mx

A

etiology:
- lens edge miniscus causing local tear film thinning leading to exposure of the cornea

signs:

  • SPK at 3 and 9 o’clock areas (or close)
  • SPK shape and appearance can vary widely
  • can have assoc adjacent limbal/conjunctival injection

symptoms:

  • discomfort/lens awareness
  • dryness, gritty, burning
  • can be asymptomatic if mild

Mx

  • px education
  • ATs
  • improve blinking
  • maximise lens wettability
  • minimize surface deposits
  • redesign lens to improve fitting
25
Q

Dellen signs, symptoms, etiology, mx

A

etiology

  • paralimbal elevation which induces a break in the pre-corneal oily tear layer and thus chronic dehydration and thinning
  • contributing factors incl; elevations such as pinguecula, pterygium, thick edge RGP, chronic tear film evaporation, chronic 3 and 9 o’clock staining

signs

  • characterised by localised thinning of the cornea in a saucer-like depression that pools with NaFl
  • often doesnt stain unless epith compromised
  • eye usually not inflamed

symptoms

  • may complain of vague irritation or photophobia
  • no pain

Mx

  • temporarily cease RGP wear to allow corneal re-epithelialisation and corneal thickness to return
  • lubrication
  • determine and manage cause e.g. minimizing 3 and 9 o’clock staining
  • if unmanaged - vascularisation, scarring, stromal inflam and degen
26
Q

Vascularised limbal keratitis signs, symptoms, etiology, Mx

A

etiology

  • mechanical insult to limbal region by edge of RGP lens
  • large diameter lenses with low edge lift
  • chronic irritation with continuous day and overnight wear may be factor

signs

  • opaque elevated mass at the nasal/temporal cornea adjacent the limbus
  • limbal vessel engorgement and conj hyperaemia with staining

symptoms

  • discomfort
  • lens awareness
  • decreased wearing time
  • redness
  • lacrimation
  • photophobia

Mx

  • cease CL wear temporarily
  • change to conservative wearing time
  • redesign lens for moderate edge lift
  • possibly reduce lens diameter
27
Q

RGP induced ptosis signs, etiology, Mx

A

etiology

  • mechanical interaction of lid riding over lens edge
  • oedema of lid tissue
  • inflammation
  • lid hypertrophy
  • nerve dysfunction
  • dehiscence of the aponeurosis of levator tarsal

signs

  • characterised by lowering of upper lid, reducing PA over time in RGP wearer
  • assoc thickened and red lids

Mx

  • temporary discontinuation of lens wear (4-12 wks)
  • refit with SCLs
  • review lens edge profile
  • refer for lid surgery
  • rule out other causes

OPTOM 430 Test (3 decks)

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