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
What material would be used for daily wear?
Consider lowest Dk to allow for optimum wettability
What material would be used for extended wear?
High Dk
