RGP For Astigmatism Flashcards
1
Q
Back surface toric design benefit
A
- physical compatibility is good for astigmatism
2
Q
Front surface toric design
A
- spherical back surface
- cyl front surface
- circular design
- truncated design
- good for lenticular design
3
Q
Front surface toric - circular design
A
- optical zone is centred
- base down prism
- increased comfort
- easier manufacture and replication
- good when lower lid below limbus
- increased physiological performance
4
Q
FST - Truncated design
A
- inferiorly truncated
- rests against lower lid
- prism ballast
- optical zone is decentred superiorly
- superior truncation to increase CL stabilising
- reduced comfort
5
Q
Bitoric design
A
- front/back surface toric gives unacceptable residual astigmatism
- toric back surface for physical fit and toric front for astigmatic correction
6
Q
Peripheral toric design
A
- spherical back optic zone
- toric back peripheral curves
- spherical front optic zone and peripheral curves
- oral/ellipsoidal shaped optic zone
7
Q
Toric GP advantages
A
- stabilised CL fit
- increased CL-Cornea fitting relationship
- better corneal physiology than toric SCLs
8
Q
Toric GP disadvantages
A
- thick lens
- reduced control of edge profile
- misaligned axis
9
Q
Aim of Bitoric fitting
A
- prevent residual astigmatism
- BS torics can induce astigmatism
- front toric correction
- calculate rx along each meridian
- aim for full alignment
