Introduction to RGP Lenses Flashcards
What is an RGP lens?
A CL made with firm durable plastic that transmits oxygen with the diameter being less than the visible iris diameter
What are advantages of RGPs?
- Better optics and VA
- Correct corneal astigmatism
- superior tear pump
- High Dk/t
- Durable
- less expensive over the life of lens
What are the disadvantages of RGPs?
- requires initial adaptation
- Lens ejection more common
- dirt/FB under lens
- corneal staining more frequent
- flare
- greater care requirements
What are the indications for RGPs?
- myopia control
- irregular astigmatism
- high refractive error
- existing wearers
- px at high risk of infection
What are the contraindications for RGPs?
- Intermittent lens wear
- contact sports
- dusty environments
- young children
- px with highly sensitive eyes
How do the eyelids help with the lens?
The lids will prevent the lens from falling out the eye
What are the parameters of rigid lenses?
- BOZR/BOZD
- Diameter
- Thickness
- Edge lift/edge clearance
What does the front surface of the lens enable?
Enables lens power and a clean wettable surface for a stable tear film
When the front surface interacts with the lids what can it impact?
the comfort, movement and centration
What does the back surface of the lens enable?
Post-lens tear film and vision and a dit by profiling the cornea
What will the total diameter of the an RGP lens be in the ranges of?
TD of a GP lens will be in the range of 8.8 - 10.0mm
What does the choice of diameter depend on?
- IPA
- pupil size
- lid geometry
- fitting philosophy
- lens design
What is the axial edge lift?
A physical property of the lens, which is determined by the final peripheral curve
What material would be used for myopes and astigmats?
- lower dk for added durability and reduced flexure
What material would be used for hyperopes?
Higher Dk due to increased centre thickness
