Contact lenses

Question 1

If a modulus is high, is the material more or less rigid?

Answer 1

More

Question 2

How much UV do sunspecs block

Answer 2

As little as 50% because of peripheral light focussing on the nasal aspect of the eye.

Question 3

What problems do soft lenses with a high modulus cause?

Answer 3

SEALS or CLPC

Question 4

What is oxygen transmissibility?

Answer 4

dk/t, property of finished lens

Question 5

What is oxygen permeability?

Answer 5

dk, property of lens material

Question 6

Which RGP lenses are more attractive to protein, silicon acrylates of fluorosilicon acrylates?

Answer 6

Silicon acrylates

Question 7

Which RGP lenses scratch most easily?

Answer 7

Fluorosilicon acrylates

Question 8

Put CAB, PMMA, SA and FSA lens materials in order of dk?

Answer 8

lowest PMMA, then CAB, then SA, then FSA

Question 9

Which is the most accurate predictor of fit in soft contact lenses?

Answer 9

Push up test

Question 10

When fitting an RGP lens on a spherical cornea what BOZR should we select?

Answer 10

BOZR = k’s

Question 11

With <0.50 DC or corneal cyl, what would your first RGP lens be?

Answer 11

fit on flattest k

Question 12

0.75-1.25DC of corneal cyl, what would your first RGP lens be?

Answer 12

fit 0.05mm steeper than flattest k

Question 13

1.50DC- 2.25DC or corneal cyl, what BOZR would you try first?

Answer 13

fit 0.1 steeper than flattest k

Question 14

If you decrease TD by 0.5mm what do you need to do to the BOZR?

Answer 14

Decrease by 0.05

Question 15

What size should an ideal BOZD be?

Answer 15

1.5mm larger than average/max pupil size.

Question 16

What size should an ideal TD be?

Answer 16

2mm smaller than HVID

Question 17

To reduce 3 and 9 o’ clock staining what could you do?

Answer 17

Increase TD,

Question 18

What types of edge lift are there?

Answer 18

radial and axial

Question 19

What is the difference between edge clearance and edge lift?

Answer 19

Edge clearance is the fluorescein fit, edge lift is a design characteristic

Question 20

what design are most modern RGP lenses

Answer 20

tricurve

Question 21

In soft lenses what size would be the ideal TD?

Answer 21

2mm larger than HVID

Question 22

What measures can be used to improve the fit of an RGP on a toric cornea?

Answer 22

Alter BOZR to minimise edge clearance in steeper meridian
Reduce TD
Use aspheric RGP with narrower edge lift
Spherical centre, toric periphery
Toric RGP

Question 23

What is the most accurate method of determining eye dominance for monovision

Answer 23

+1.25 blur, the one which blurs the most.

Question 24

How would you fit a RGP to a KC. First BOZR and fitting philosophy.

Answer 24

0.2 steeper than mean k

3 point touch