Week 4 Quiz Revision

Question 1

How many curves are in a RGP lens? And what are they

Answer 1

3 Curves
Periphery curve
secondary curve
base curve

Question 2

The edge of an RGP lens is divided into 3 zones. What are they?

Answer 2

Posterior zone
Anterior zone
Apex zone

Question 3

The radiuscope is used to determine the power of an RGP lens. T/F

Answer 3

False - the radiuscope measures the BC. the lensmeter measures the power

Question 4

The image in a radiuscope comes into focus but the images are not 090 degress aprt. This means the lens is warped. T/F

Answer 4

TRUE

Question 5

What 3 methods are used to inspect the RGP lens edge?

Answer 5

Slit lamp/ Biomicroscope
Measuring Magnifier
Projection Magnifier

Question 6

Identify the style of the RGP.

In the lensmeter you measure -3.00/-4.00. In the radiuscope you measure 7.83mm

Answer 6

Front Toric

Question 7

Identify the style of the RGP.

In the lensmeter you measure -3.00/-4.00. In the radiuscope you measure 7.50/7.03. 45.00/48.00

Answer 7

Bi Toric as the residual astigmatism is above 0.75D

Question 8

If the tear lens under the RGP, sitting against the cornea is a plus power how has the lens been fit?

Answer 8

Steeper than K

Question 9

What does FAP indicate? 2

Answer 9

Add plus to the CL RX
The tear lens forms a minus power against the cornea.

Question 10

What does SAM indicate? 2

Answer 10

Add minus to the CL RX
The tear lens forms a plus power against the cornea

Question 11

What does the keratometer measure?

Answer 11

The corneal cap

Question 12

What does BC stand for?

Answer 12

Base Curve

Question 13

A plus powered lens moved towards the eye is effectively………..

Answer 13

More minus (weaker)

Question 14

What is the purpose of the radiuscope?

Answer 14

Measure the base curve of a lens

Question 15

What is the design of the RGP if it has 2 base curves and a spherocylinder reading in the lensmeter and 2 powers on the lab order?

Answer 15

Bi-Toric lens

Question 16

If the RGP lens has 2 back curves and 2 spherical powers reading in the lensmeter? There is only one power on the lab order. What design is this lens?

Answer 16

Back Toric lens

Question 17

If the lens is too thin and bends on the blink this is known as what?

Answer 17

Flexure

Question 18

What does DK stand for?

Answer 18

Oxygen Permeability

Question 19

An eyeglass wearer just got fitted for contact lenses. He wears +12.00D OU eyeglasses. The power in his contact lens (compensated power) should be a higher plus or lower plus than his eyeglasses?

Answer 19

Higher Plus

Question 20

A radisucope reading of an RGP shows the lens only has one curve and when the power is checked it is determined that it is sphero-cylinder. What type of lens design is this?

Answer 20

Front Toric Lens

Question 21

When a person is wearing spectacles and a refraction is conducted over the spectacles. It is found that both the eyeglasses and the over refraction have two spherocylinder prescriptions with different axis. What is this known as?

Answer 21

Obliquely crossed cylinders

Question 22

Which equipment is used to determine if a fit of an RGP is steep or flat?

Answer 22

Slit Lamp, fluorescein and colbalt blue filter

Question 23

What does DK/t stand for?

Answer 23

Oxygen Transmissibility

Question 24

What is used to measure corneal thickness?

Answer 24

Pachymeter

Question 25

A patient comes in complaining of not being able to wear their lens due to comfort and blurred vision while wearing the lenses. What is the probable cause?1 What is it NOT and why?2

Answer 25

Scratches and/or dirty lens
(not corneal edema as blurry only with CL on)
(not fit as they ‘come back’ complaining and we would have fit well)

Question 26

What does HVID stand for?

Answer 26

Horizontal visible Iris diameter

Question 27

If the K’readings is: 43.00 sphere but fit at 42.00. CL RX is: -3.00D What is the new lens power?

Answer 27

-2.00D (FAP. it was fit 1.00 flatter than K so -3.00+1.00=-2.00)

Question 28

If the RGP lens shows no movement/adhesion on the lens. Would this indicate a flat fit or steep fit?

Answer 28

Steep fit

Question 29

What does BOZD stand for?

Answer 29

Back Optic Zone diameter

Question 30

What does the v-gauge measure?

Answer 30

Diameter of a RGP lens

Question 31

If the radiuscope shows 1 curve and the lensmeter shows one power. What type of RGP lens is this?

Answer 31

Spherical

Question 32

What is the corneal cyl of 41.00/41.75 @090?

Answer 32

-0.75D (MUST BE MINUS)

Question 33

The px K’reading: 44.00/45.00 @090 The fitter fits 43,75 flattest K. Is it fit flatter/ on K or steeper?

Answer 33

flatter

Question 34

What is the main advantage of switching from a PMMA to RGP lens?

Answer 34

Oxygen Permeability (DK)

Question 35

If the spokes on a radiuscope all come into focus the same time this tell you what about the lens?

Answer 35

There is only one curve (spherical)

Question 36

If you are making an Bi Toric or Back Toric lens once you have found DIA/BC what do you do? next 3 steps

Answer 36

-Find ∆k 2.75D
-Find induced cyl = ∆K X 0.4 1.1D
-Find Calculated over correction (Coc)= induced cyl - Residual cyl

a. If Coc <0.75 use back toric
b. If Coc > 0.75 use bi-toric

Question 37

Once the COC has been found and the design has been confirmed, you use the orginal two vertexed meridians with the residual cyl to find the final power and apply FAP/SAM to. T/F

Answer 37

true