RGP selection Flashcards
RGP
What is TD?
Total diameter of the lens
RGP
What is BOZR?
Back Optic Zone Radius
i.e. the radius of curvature of the optic zone of the lens
RGP
What is BOZD?
Back Optic Zone Diameter
i.e. the diameter of the optic zone of the lens
RGP
What is BOZR chosen according to?
Keratometry - the curvature of the corneal surface
RGP
What is BOZD chosen according to?
Max pupil size (1.5mm bigger)
RGP
If the BOZD is too small, what might happen?
Px looks through peripheral curves, causing flare
RGP
What is TD based on?
HVID (2mm smaller)
RGP
Do the peripheral curves get flatter or steeper towards the edge of the lens?
Flatter
RGP
What do the peripheral curves help with?
Tear film exchange
Lens removal
RGP
What is edge clearance?
The horizontal gap between the cornea and back surface of peripheral curves (to edge of lens)
How wide the gap is from the cornea to the edge of the lens
RGP
What is radial edge lift?
Vertical gap between cornea and back surface of the edge of the lens
Parallel with cornea
RGP
What is axial edge lift?
Vertical gap between cornea and back surface of the edge of the lens
Perpendicular to cornea
What three things are you aiming for when fitting an RGP?
Mimicking of corneal curvature with the back surface of the lens
Evenly distributed pressure on the cornea (more comfortable
Enough edge clearance to allow tear exchange/lens removal
On fluorescein examination of an RGP fit, what does a darker area mean?
That part of the lens is closer to the cornea than brighter areas
How much of the cornea does keratometry measure?
Central 3-4mm
