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III. Advanced Contact Lenses > GP Toric (M1) > Flashcards

GP Toric (M1) Flashcards

1
Q

What are the things that are required to put in the order for a front surface toric GP?

A
  1. base curve
  2. diameter
  3. prism (with dot at base) about 1.25pd
  4. power in spherocylindrical notation with axis
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2
Q

What are the traits of a low toric simulation fit?

A
  1. BC aligns (+/- 0.25D) with flat meridian and undercorrects steep meridian
  2. diameters bigger
  3. toric lacrimal lens
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3
Q

If a spherical lens is fit too flat or too steep what does it cause?

A

corneal molding

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4
Q

What are the readings for the lensometer for a front surface GP toric? 1. Readings for radioscope? 2

A
  1. some cyl

2. spherical

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5
Q

What is the most common type of toric GP lens?

A

bitoric GP

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6
Q

What is the cyl on the eye lead to on a back surface toric GP? 1. What does the cyl measured on the radioscope measure? 2. Cyl on the lensometer? 3

A
  1. induced cyl
  2. base curve toricity
  3. air cylinder
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7
Q

How is the power for a bitoric GP lens written?

A

specify BC and power for each meridian but not in spherocylindrical form and no need for axis specification

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8
Q

What is the equation to find the center thickness of a toric GP lens?

A

use power than yields largest CT (most plus)
CT(minus lens) = 0.18 + 0.01(power)
CT(plus lens) = 0.18 + 0.02(power)

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9
Q

When is it best to used a back surface toric GP lens?

A

spectacle astigmatism is about 1.5X corneal toricity (3:2:1 rule, 3 cyl power (lenso), 2 BC toricity (radioscope), 1 induced cylinder (on eye))

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10
Q

What are the readings for the lensometer for a bitoric GP? 1. Readings for radioscope? 2

A
  1. cyl

2. cyl

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11
Q

What are the readings for the lensometer for a back surface GP toric? 1. Readings for radioscope? 2

A
  1. cyl

2. cyl

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12
Q

What is the bitoric where the difference in the BC is not the same the difference in lens power? 1. What does this mean? 2

A
  1. cylindrical power effect (CPE)

2. rotation induces cylinder power

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13
Q

When calculating bitoric lenses empirically, what is used?

A
  1. optical crosses

2. Mandell-Moore Bitoric worksheet

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14
Q

What type of corneal toricity is best for a low toric simulation fit?

A

K toricity greater than 2.50D (better WTR astig)

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15
Q

When are GP toric lenses required?

A
  1. spherical GP’s do not correct all refractive error (tear lens does not correct all astig)
  2. corneal cyl does NOT equal refractive cyl
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16
Q

How do you adjust the a CPE bitoric to make it SPE?

A

adjust powers of lens (creates more visually acceptable residual astigmatism)

17
Q

When calculating bitoric lenses diagnostically, what is used?

A
  1. spherical trial lens

2. SPE trial lens

18
Q

What type of corneal toricity is best for a full alignment (or saddle fit)?

A

2.00 to 2.50D K’s

19
Q

What is the bitoric where the difference in the BC is the same as the difference in lens power? 1. What does this mean? 2

A
  1. spherical power effect (SPE)

2. any cyl induced rotation is corrected by tear lens

20
Q

What are the traits of a full alignment (or saddle fit)?

A
  1. on K for each meridian
  2. tighter fit, more centered so smaller diameter (interpalpebral fit)
  3. spherical lacrimal lens
21
Q

What type of astigmatism do soft toric lenses correct?

A

refractive astigmatism

22
Q

What are the two aspects that make up the refractive astigmatism?

A
  1. corneal astig

2. lenticular astig

23
Q

When ordering a toric GP lens, what should be the peripheral curve BC? 1. How wide? 2

A
  1. BC + 3.0mm

2. 0.2mm wide

24
Q

What are the three types of GP toric lenses?

A
  1. front surface GP toric
  2. back surface GP toric
  3. bitoric GP
25
Q

What occurs as a result of a back surface toric?

A

lens induces cyl created by changes in index of refraction from lens material to tears

26
Q

Where is the cylinder induced by a back surface toric located?

A

flat meridian of CL

27
Q

What is used to determine if the bitoric lens resulted in SPE or CPE?

A

difference in bace curve and difference in the power of the lens

28
Q

What are the indications for a front surface toric GP?

A
  1. 1 D or more residual astig
  2. 2 D or less corneal toricity
  3. poor fit with soft toric
29
Q

When ordering a toric GP lens, what should be the secondary curve BC? 1. How wide? 2

A
  1. BC + 1.0mm

2. 0.4mm wide

III. Advanced Contact Lenses (16 decks)

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