Contact Lens SEMINAR 3

Question 1

How would you describe this fluorescein pattern?

A. Steep

B. With the rule

C. Against the rule

D. Aligned

E. Flat

Answer 1

E. Flat

Question 2

What are the three main aims of an RGP contact lens fitting?

Answer 2

Good visual performance

Minimal ocular response

Optimised comfort

Question 3

How do we achieve our three main aims with an RGP fitting?

A. Steep fluorescein pattern, by fitting 0.1mm flatter than the flattest K

B. Aligned fluorescein pattern, by fitting on average K [(Kf + Ks) / 2]

C. Aligned fluorescein pattern, by fitting on flattest K (or slightly steeper in case of significant corneal astigmatism)

D. Flat fluorescein pattern, by fitting 0.1mm flatter than the flattest K

Answer 3

C. Aligned fluorescein pattern, by fitting on flattest K (or slightly steeper in case of significant corneal astigmatism)

Question 4

Following standard fitting guidelines, which RGP lens would you trial?

Ocular Rx: -4.50/-0.50 x 5

Keratometry: 7.90 @ 180 7.80 @ 90

HVID: 12mm

VPA: 9mm

You have the following options:

A. 7.90/ 10.00 -4.50

B. 7.90/ 9.80 -4.50DS

C. 7.85/ 10.00 -4.75DS

D. 7.85/10.00 -4.50DS

[K fitting]/[Diameter of the lens] [PWR]

Answer 4

7.90 / 10.00 -4.50

( Don’t worry about the cyl as RGPs can be overcome small amounts of cyl)

Question 5

Your patient is wearing a lens with the following specifications:

7.50/ 9.30 -3.00DS

The FP is as follows: ( see image)

The over refraction is surprisingly PLANO with VA of 6/5 ( basically this means that the power of the lens was correct).

You decide to make the lens significantly flatter, by 0.20mm.

The new RGP specification will be which one of the following?

A. 7.52/ 9.30 -3.00DS

B. 7.30/ 9.30 -1.00DS

C. 7.70/ 9.30 -2.00DS

D. 7.70/ 9.30 -3.00DS

Answer 5

C. 7.70/ 9.30 -2.00DS

( Rememebr your rule of thumb for making flatter 0.05 = 0.25D change in power — in this case 0.20mm flatter = +1.00DS change in BVP )

Question 6

Smooth edge rounding is important for px comfort - on which side of the lens is it most important to have the smooth edge thus which one one out of B and C will be most comfortable for the px?

Answer 6

Overall its good to have a smooth edge profile ( like A) but ultimately anterior edge rounding is more important than posterior edge rounding ( i.e. edge that comes in contact with eyelids affects px comfort the greatest) thus B will be more comfortable than C.

Question 7

Which of the follwoing edge roundings will be most comfortable for the px?

Answer 7

A

[Poor edge rounding à greater edge awareness by the upper eyelid and thus discomfort]