week 3

Question 1

Name one or two examples of aspheric CL brands:

Answer 1

Frequency 55 Aspheric
– Biomedics 55 Premier / Avaira
– PureVision / PureVision2
– Definition AC

Question 2

soft toric lenses often work well for patients with what kind of astigmatism?

Answer 2

Soft lenses often work well for patients with lenticular

astigmatism and ATR corneal cyl

Question 3

For ATR corneal astigmatism in soft toric lenses, what kind of decentration is common

Answer 3

lateral decentration is common

Question 4

For lenticular astigmatism, what is the best type of toric lens?

Answer 4

For lenticular astigmatism, a front surface toric GP is required

Question 5

Soft Toric Lenses work best for patients with how much astig?

Answer 5

Soft Toric Lenses work best for patients with moderate

refractive astigmatism

Question 6

T/F: The less the cylinder component is compared to the

spherical component, the better the results

Answer 6

True

Question 7

Higher myopia correlated with less stability in what kind of designs of toric lenses?

Answer 7

Higher myopia correlated with less stability in prism

ballasted designs

Question 8

Lower myopia correlated with less stability in what kind of designs of toric lenses?

Answer 8

Lower myopia correlated with less stability in double

slab-off designs

Question 9

What are the 3 most influential characteristics on lens

stability:

Answer 9

1) Palpebral aperture size
2) Degree of myopia
– Higher myopia correlated with less stability
3) Lid angles

Question 10

what palpebral aperture size corresponds to greater stability?

Answer 10

Smaller PA correlated with greater stability

Question 11

what is a positive intercanthal angle and what kind of rotation is it associated with?

Answer 11

Positive angle=temp lid higher than nasal

• correlated with temporal rotation
• *Positive angle more common

Question 12

what are some of the tolerances and success rates of cyl axes of 20, 15, 10 and 5 degrees?

Answer 12

• Rotation± 20- success rate is 90% for soft torics
• Rotation± 15- success rate is 90% with 2 lenses
• Rotation± 10- success rate is 70% with 3 lenses
• Rotation±5- Patient must accept variable vision with soft torics

Question 13

where are the thickest edges on a toric WTR soft CL? ATR? oblique?

Answer 13

• WTR: thicker edge at top and bottom
• ATR: thicker edge at nasal and temporal
• Oblique: thicker edge along more minus meridian
• For all: greater edge thickness with greater
myopia, which interacts more with eyelids

Question 14

T/F: In most modern designs, toricity is limited to the optic zone so that it does not affect the fit or rotation of the lens when on the eye

Answer 14

true

Question 15

what is prism ballasting?

Answer 15

incorporating 0.75–2.00 D of base down prism into the CL

Question 16

what is peri-ballasting?

Answer 16

Peri-ballast incorporates prism in peripheral (carrier) portion only, so no optical prism effect. Most modern designs do this instead of full prism ballast

Question 17

what is the “Watermelon seed effect”?

Answer 17

if a moist, rounded-off wedge is squeezed, it will be expelled towards its base down direction

Question 18

Acuvue Advance/Oasys for Astigmatism use what method for prism stabilization?

Answer 18

“Accelerated Stabilization Desig”

-Active zones (thicker middle zones that force lens into place when acted upon by lid)

Question 19

what is eccentric lenticulation?

Answer 19

[method for stabilizing lens] a front surface off center (eccentric) lenticular cut in the direction of the prism apex

Question 20

T/F: markings on a toric lens indicate the location of the cylinder axis

Answer 20

FALSE

Question 21

cyl power comes in what power steps generally for standard soft toric lenses?

Answer 21

0.50 D

Question 22

which is more important for fitting soft torics: the refractive cylinder or the corneal toricity

Answer 22

The refractive cylinder, not the corneal toricity, is the primary concern for fitting soft torics

Question 23

T/F: The higher the refractive sphere correction, the

greater tolerance for uncorrected cylinder

Answer 23

True

Question 24

In general, soft toric lens should not rotate more than __

degrees

Answer 24

15-20 degrees

If so, another base curve or lens design should be tried

Question 25

Lens should not rotate more than –° during the blink

Answer 25

Lens should not rotate more than 5 to 10° during the blink

Question 26

What is the Challenge test to assess Assess rotational stability?

Answer 26

Challenge test: manually rotate lens to off axis position and see how long it takes to return to original position
**should be less than 30 seconds