CLM - Nomenclature and Verification of CLs - Week 2 Flashcards
Describe the 5 steps in contact lens practice.
Full eye test
CLs fitting
CLs delivery/teaching
CLs Aftercare
CLs refitting - as needed
Define BOZR.
Back optic zone radius
Define BODZ.
Back optic zone diameter
Define BPR.
Back peripheral radius
Define BPZD.
Back peripheral zone diameter
Define TD.
Total diameter
Define FOZR.
Front optic zone radius
Define FOZD.
Front optic zone diameter
Define BVP.
Back vertex power
Define CT.
Centre thickness
Define ET.
Edge thickness
Define Dk.
Oxygen permeability
Define Dk/t.
Oxygen transmissibility
What tool is used to verify the base curve in RGPs?
Radiuscope
What three techniques are used to verify the base curve of SCLs?
Template method
Radiuscope
Spherometer
Briefly describe how a radiuscope works (3).
The curved surface of a CL acts as a mirror
Two images are formed, a surface image and an aerial image (cleaner)
Distance between focussing these two images gives radius of curvature
Describe the procedure to set up a radiuscope (4).
Ensure CLs are clean
Place a drop of saline in the lens mount
Place lens convex surface down on the drop
Withdraw excess liquid
Describe the procedure to use a radiuscope to measure radius of curvature (4).
Centre on the CL
Set the internal scale to zero
Obtain aerial focus by moving the scope up
Read off the internal scale for radius
Use an average of 3 readings
In what mm increments should radius of curvature be taken?
0.05mm
Describe how the template method is carried out (3).
Master spheres of known curvature are used
Lens is placed concave side down
If the two surfaces are not aligned, a bubble forms
In what type of CLs is BPR measured?
RGPs
In what type of CLs is FOZR measured?
RGPs
