Multifocal Contacts and Presbyopia

Question 1

What type of RX would work best for monovision contacts?

Answer 1

Spherical or those with a distance power between -4.00 and +6.00

Question 2

How would the contact lens fitter determine which eye is dominant for monovision contacts?

Answer 2

Triangle test or telescope test

Question 3

What is the starting point for monovision fit?

Answer 3

Utilizing the distance power for the dominant eye and then near power for the non dominant eye

Question 4

Who are some bad patient candidates for multifocal contacts?

Answer 4

1. Hyperopes or Emmetropes who have not worn correction before

Question 5

How would the fitter assess and measure pupil size to determine which contact may be best?

Answer 5

1. Normal Room Light
2. Slit lamp/white light for bright conditions
3. Low light and cobalt blue filter for nighttime conditions

Question 6

Explain Alternating Bifocals

Answer 6

Look like a segmented multifocal lens, the lower lid holds the lens in place so when the patient looks down the pupil looks down into the segment.
These are the clearest acuity but difficult to fit.

Question 7

Explain how you would fit a gas permeable multifocal lens

Answer 7

1. Fit flatter than K
2. Stabilize with prism, slab off, or slight truncation
3. Lid placement is priority, positions inferiorly and rests on the lower lid
4. Seg height starting point is 1 mm below geometric center of the lens

Question 8

What is a crescent design (fused) contact?

Answer 8

This design maintains near vision even if the patient has lens rotation. This would not work if the patient has a narrow palpabral fissure or loose lower lid

Question 9

What is a crescent design (1 piece) contact?

Answer 9

Similar to fused, but has a larger reading area so they are ideal for individuals to maintain near vision for extended periods

Question 10

What is an inverted crescent contact design?

Answer 10

Ideal for those with critical distance needs because of better rotation and peripheral vision. This design can also be spherical, aspheric and toric.

Question 11

What is a straight top contact lens design?

Answer 11

You would need a prism ballast to maintain orientation, but usually allows pts to see clear with up to 20 degrees orientation.

Question 12

What is a decentered distance segment lens design?

Answer 12

Great for individuals with extensive near needs or those who need to see up close above eye level

Question 13

Why is a slight inferior upward nasal rotation preferred if the contact rotates?

Answer 13

Because the eye converges when looking at near, so it is easier to read if this occurs

Question 14

What is the most common remedy for stablilization for excessive upward rotation?

Answer 14

Prism, to decide where to put the prism, you would use RALS.

Question 15

What are four points to check if the patient complains of distance vision in multifocal lenses?

Answer 15

1. Is the seg height correct
2. Does the lens drop quickly after blinking
3. How is the rotation
4. Is the seg type correct?

Question 16

What are two points to check if the patient complains of near vision in multifocal lenses?

Answer 16

1. Check positioning, translation and rotation before adjusting add power
2. If complaint is intermediate, the fitter can slightly overplus the distance of non dominant eye to assist.

Question 17

How do simultaneous design contacts work?

Answer 17

Blends prescriptions for near and distance, this works because it relies on the way we select a clearer image when needed.

Question 18

What is a concentric design multifocal lens?

Answer 18

Can have either a near power center or distance power center, This design can have slight translation or no translation

Question 19

What is a multizone design multifocal lens?

Answer 19

These lenses are designed to minimize the dependency on pupil size.

Question 20

To improve VA in the near, the fitter would:

Answer 20

Dominant Eye: Increase OZ, Non Dominant Eye: None or Decrease OZ

Question 21

To improve VA in the distance the fitter would:

Answer 21

Dominant eye: None or decrease OZ Non Dominant Eye: Decrease OZ

Question 22

To improve VA in the near and distance, the fitter would:

Answer 22

Dominant Eye: None or increase OZ, Non Dominant Eye: Decrease OZ

Question 23

To improve VA in the intermediate, the fitter would:

Answer 23

Dominant Eye: Increase OZ, Non Dominant Eye: None or decrease OZ

Question 24

To improve VA in the distance and intermediate, the fitter would:

Answer 24

Dominant Eye: None or increase OZ, Non Dominant Eye: Decrease OZ

Question 25

How are aspheric curves defined by their eccentricity value?

Answer 25

The E- value is a measure of how far the curve deviates from the circle shape. The steeper circular shape has an e value of 0, and the higher the e value becomes the flatter the shape becomes.

Question 26

In GP lenses, the E value impacts fit by:

Answer 26

1. The lower the e value, the tighter the fit 2. The higher the e value, the looser the fit 3. To adjust fit, change e values not base curve

Question 27

Explain Front surface aspheric contact lenses

Answer 27

1. Used in the center near designs 2. Better for low presbyopes 3. Soft front surface aspheric lenses use front negative spherical aberration to shift power from near to distance

Question 28

Explain a center distance contact lens

Answer 28

Uses back aspheric curves to induce positive powered spherical aberrations that gradually produce add power. The greater the e value for the back surface, the greater the difference between the distance and add power

Question 29

Explain a center near contact lens

Answer 29

These were created because the pupil constricts when looking at near and therefore cannot reach the near zones. Main drawback to this design is that distance is blurry in low light conditions.

Question 30

Explain a Zonal aspheric design

Answer 30

1. Combines aspheric and concentric designs 2. Allows for near, distance and intermediate correction 3. Allows for low, mid and high add power 4. Allows for pupil variations 5. Back surface aspheric to maintain centration