CLM - Nomenclature and Verification of CLs - Week 2

Question 1

Describe the 5 steps in contact lens practice.

Answer 1

Full eye test
CLs fitting
CLs delivery/teaching
CLs Aftercare
CLs refitting - as needed

Question 2

Define BOZR.

Answer 2

Back optic zone radius

Question 3

Define BODZ.

Answer 3

Back optic zone diameter

Question 4

Define BPR.

Answer 4

Back peripheral radius

Question 5

Define BPZD.

Answer 5

Back peripheral zone diameter

Question 6

Define TD.

Answer 6

Total diameter

Question 7

Define FOZR.

Answer 7

Front optic zone radius

Question 8

Define FOZD.

Answer 8

Front optic zone diameter

Question 9

Define BVP.

Answer 9

Back vertex power

Question 10

Define CT.

Answer 10

Centre thickness

Question 11

Define ET.

Answer 11

Edge thickness

Question 12

Define Dk.

Answer 12

Oxygen permeability

Question 13

Define Dk/t.

Answer 13

Oxygen transmissibility

Question 14

What tool is used to verify the base curve in RGPs?

Answer 14

Radiuscope

Question 15

What three techniques are used to verify the base curve of SCLs?

Answer 15

Template method
Radiuscope
Spherometer

Question 16

Briefly describe how a radiuscope works (3).

Answer 16

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

Question 17

Describe the procedure to set up a radiuscope (4).

Answer 17

Ensure CLs are clean
Place a drop of saline in the lens mount
Place lens convex surface down on the drop
Withdraw excess liquid

Question 18

Describe the procedure to use a radiuscope to measure radius of curvature (4).

Answer 18

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

Question 19

In what mm increments should radius of curvature be taken?

Answer 19

0.05mm

Question 20

Describe how the template method is carried out (3).

Answer 20

Master spheres of known curvature are used
Lens is placed concave side down
If the two surfaces are not aligned, a bubble forms

Question 21

In what type of CLs is BPR measured?

Answer 21

RGPs

Question 22

In what type of CLs is FOZR measured?

Answer 22

RGPs