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Contact Lens I Part 2 > Contact Lens 1-2: Spherical Soft CL Fitting > Flashcards

Contact Lens 1-2: Spherical Soft CL Fitting Flashcards

1
Q

What are the 4 Main CL Manufacturers? (ABCV)

A
  1. Alcon (Ciba)
  2. Bausch + Lomb
  3. Coopervision
  4. Vistakon (Johnson & Johnson)
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2
Q

Hydrogel Vs. Silicone Hydrogel

  1. Hydrogel: What is it?
  2. Silicone Hydrogel (SiHy)
    a. What does Silicone do?
A
  1. PMMA w/an Extra -OH group
  2. Hydrogel with added SILOXANE Groups
    a. Increases O2 Permeability
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3
Q

Replacement Schedules

  1. Alcon:
    a. Name of CLs?
    b. Replacement schedule?
  2. Bausch + Lomb
    a. Name of CLs?
    b. Replacement Schedule?
  3. Coopervision
    a. Name of CLs?
    b. Replacement Schedule?
  4. Vistakon
    a. Name of CLs?
    b. Replacement Schedule?
A
  1. a. Air Optix
    b. Monthly
  2. a. Purevision and Purevision 2
    b. Monthyl
  3. a. Biofinity
    b. Monthly
  4. a. Acuvue
    b. 2 wks (except for daily disposables)
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4
Q

FDA Standards for UV

  1. Class 1 Blocker
    a. Use for what places?
    b. % blocker of UVA?
    c. % Blocker of UVB?
  2. Class II Blocker
    a. Main use?
    b. UVA block %?
    c. UVB block %?
A
  1. a. High exposure environments like Mountains or Beaches
    b. 90%
    c. 99%
  2. a. General Purpose
    b. 70%
    c. 95%
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5
Q

Water Content

  1. SCL ABSORBS water and does what?
  2. Water content: How is it read in Tyler’s?
A
  1. it Swells

2. % of H2O of TOTAL LENS WEIGHT!

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6
Q

Effect of Water Content on Hydrogel SCL

  1. As Water Content INCREASES, what happens to the following?
    a. Strength
    b. Deposit Resistance
    c. RI
    d. Pore Size
    e. O2 Permeability
    f. Safety of Heat Disinfection
A
  1. *Everything DECREASES except for Pore Size and O2 Permeability
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7
Q

FDA Grouping of SCL

  1. Group 1
    a. Ionicity
    b. H2O Content
  2. Group 2
  3. Group 3
  4. Group 4
A
  1. a. Non Ionic
    b. Low Water
  2. a. Non-Ionic
    b. High Water
  3. a. Ionic
    b. Low Water
  4. a. Ionic
    b. High Water

*HIgh water = 50% or more

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8
Q

Ionicity

  1. Ionic Materials: What does this mean?
  2. Non-Ionic Materials?
  3. What happens to Deposit Resistance w/Increased Ionicity?
A
  1. Net Negative Charge on the Surface
  2. Charged sites w/in polymer matrix, but NO NET SURFACE CHARGE
  3. It DECREASES
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9
Q

FDA Approval for Wearing Schedule

  1. Lens submitted to FDA. A request is made for use of the lenses (2)
A
  1. Daily Wear (no sleep in lenses) and Extended Wear (w/specified amt of time)
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10
Q

Wearing Schedule

  1. DW
  2. FW
  3. EW
  4. CW
A
  1. No sleep
  2. Flexible Wear (Occasional)
  3. Sleep in less than or equal to 6 nights
  4. More than 6 nights of sleep in them. (30 days)
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11
Q

FDA approved lenses for some form of EW

  1. Alcon
    a. Air Optic Aqua Line
    b. Air Optix Night and Day
  2. Bausch + Lomb
    a. Purevision
    b. Purevision 2
  3. Coopervision
    a. Biofinity
  4. Vistakon
    a. Acuvue Oasys
A
  1. a. 6 nights EW
    b. 30 days CW
  2. a. 30 days CW
    b. 30 days CW
  3. a. 6 nights EW
  4. a. 6 nights EW
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12
Q

O2 Permeability

  1. What is it?
  2. Dk in Hydrogel?
  3. SiHy?
A
  1. Inherent Ability of a Material to let O2 through (aka: Dk value)
  2. Lower Dk
    a. As H2O content increases, Dk value starts to increase (around 80/90% it’s the same as SiHy lenses)
  3. Higher Dk (SiHy…Sigh HIGH)
    a. As Water content increases, Dk value starts to decrease
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13
Q

O2 Transmissibility

  1. Dk/t (Dk/L): What does this tell us?
    * How is Dk measured overall? (where on the CL and at what POWER?)
A
  1. Thickness of lens (t or L) is factored in, and thickness varies w/lens power AND Location.
    * Dk/t for a given lens is quotes using the THINNEST POINT of a -3.00 D Lens
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14
Q

Lens Thickness

  1. Where is Sagitta Largest in + Lens?
  2. In a - Lens?
A
  1. At the Center of the Lens

2. At the Edge of the Lens

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15
Q

Dk/t Minimums

  1. For DW?
  2. For EW?
A
  1. At least 24.1 (Dk/t)

2. At least 87.0 (Dk/t) to reduce overnight corneal edema to 4% (what’s experienced w/o a CL in place)

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16
Q

Tear Exchange

  1. GPs Exchange what % of the underlying Tear Layer Per Blink?
  2. SCL promotes/inhibits minimal tear exchange?
  3. Cornea wearing SCL depends on what for O2?
A
  1. 10-20%
  2. PROMOTES
  3. on the Dk/t
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17
Q

Dk/t Ranges

  1. hydrogels?
  2. SiHi?
A
  1. 10-30

2. 86-175

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18
Q

3 Complications of Hypoxia?

A

Corneal Edema; Limbal Hyperemia; and Neovascularization

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19
Q

Modulus of Elasticity

  1. What is it? (3)
  2. Modulus of Elasticity higher in what type of CLs?
A
  1. a. Ability to KEEP Shape when stressed
    b. Resistance to Deformation
    c. Modulus = Stress/Strain
  2. Modulus of SiHy > Hydrogel Lenses
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20
Q

Higher Modulus of Elasticity

  1. Advantages (2)
  2. Disadvantages (2)
A
  1. Easier HANDLING; Masking of Astigmatism

2. Complications and Discomfort

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21
Q

2 Ways of Fitting

  1. Diagnostically
  2. Empirically
A
  1. trying lenses on to find best fit/power

2. Calling in Rx and ordering first lens to try on

22
Q

Choosing a Lens

  1. 3 things
A
  1. Brand –> BC/Diameter –> Power
23
Q

Guidelines

  1. What lenses are Inherently More Wettable?
    a. Why is this?
    b. What can counteract the other type?
  2. SCL w/an FDA indication for DRY Eye?
A
  1. Hydrogel
    a. Due to LACK of Hydrophobic Siloxane Groups

b. Surface Txs work to counteract this effect in SiHy lenses
2. Proclear: Hydrogel SCL made by Coopervision

24
Q

Methods for Determining BC

  1. 2 Diagnostic Methods
  2. 3 Empirical Methods
A
  1. a. Fitting guide
    b. Clinical Evaluation
  2. a. mm Method
    b. Dioptric Method
    c. Range Method
25
Q

Fitting from a Diagnostic (trial) Lens Room:

  1. options after choosing a brand?
  2. A Given lens may come in how many BCs?
  3. Consider values of what?
  4. What do you do next?
A
  1. Are Limited
  2. can come in 1, 2, or 3 BCs at the most
  3. Consider K Values
  4. Put Lens on, Assess the Fit, and Proceed
26
Q

Empirical Methods

  1. mm Method
    a. How much flatter than Flat K?
    b. How do you figure it out?
    c. STARTING BC?
A
  1. 0.8-1 mm Flatter than Flat K
    a. Convert the FLATTER K to mm
    b. Add 0.8 mm to that number (42.75 D)
    c. 8.7 mm
27
Q

Empirical Methods

  1. Dioptric Method
    a. How much flatter than Flat K?
    b. how do you figure it out?
A
  1. a. 4 D Flatter than Flat K
    b. Subtract 4.00 D from the Flattest K then convert to mm.

*Starting BC = 8.7 mm (example she did w/42.75 D as the flattest K)

28
Q

Empirical Method

  1. Range Method
    a. Flat K is greater than what?
    b. Flat K ranges?
    c. Flat K is less than what?
A
  1. a. > 45.00D, fit w/STEEPER BCR
    b. 41-45.00 D: Fit w/Median BCR
    c. <41.00 D: Fit the FLATTER BCR
29
Q

BC Radii

  1. What is considered a STEEP BC?
  2. Flat BC?
  3. Can you compare BC b/w Lens designs?
A
  1. BC = 8.5 mm
  2. Flat = 9.5 mm (BC)
    * Smaller the number, the Steeper the BC
  3. NO! Only compare BC w/in the SAME LENS DESIGN!!
30
Q

Lens comparison b/w Brands

  1. What factors do we need to consider?
A

Material, Overall Diameter, Optic Zone Diameter, Peripheral Curves, Asphericity….all affect lens fit.

31
Q

CL Fitting from Trial Lens Set

  1. Each Brand comes in what OAD?
  2. Once you select a brand, you’re committed to what?
  3. What diameter is EASIER TO HANDLE?
A
  1. only comes in 1 OAD
  2. to its diameter
  3. a SMALLER DIAMETER
32
Q

Ideal Diameter for a Custom Lens

  1. What size?
    * CL Rx: Even if lens only comes in 1 BC and/or Diameter, ALL PARAMETERS HAVE TO BE SPECIFIED!
A
  1. 2 mm LARGER than HVID
33
Q

SCL Types

  1. 4 types?
A
  1. Spherical
  2. Toric
  3. Multifocal (Toric Multifocal)
  4. Color
34
Q

Determining Spherical SCL Candidacy

  1. What do you do?
  2. Compensated Power: F compensated = ?
A
  1. VERTEX each meridian that is greater than or equal to 4.00 DS

and If Take Spherical Equivalent of Vertexed Rx

  1. F/(1-dF) (+) d when lens is moved TOWARDS THE EYE!!
35
Q

Once a Lens is on a Patient

  1. What 2 things do you do?
A
  1. Vision (Acuity and Over-Refraction)

2. Fit: Slit lamp assessment

36
Q

Over-Refraction

  1. When is Phoropter not ok?
    a. how is it done?
A
  1. When using Presbyopic Lens Options
    a. Present Spherical Lenses to Pt MONOCULARLY while they’re wearing CL and ask for subjective feedback.
    * O/R > or equal to +/- 4.00 D needs to be VERTEXED!
37
Q

What 3 things need to be assessed in SCL Fit?

A
  1. COVERAGE
  2. CENTRATION
  3. MOVEMENT
38
Q

Limbal Coverage

  1. What’s desired?
    a. What’s Acceptable?
    b. What’s Unacceptable?
A
  1. MINIMUM of 0.5 mm coverage onto Sclera (Past Limbus) 360
    a. Complete Limbal Coverage 360 and No Crossing of Limbus during Blink
    b. Any area of Limbus Exposed; and Crossing of Limbus during blink
39
Q
  1. Acceptable Centration?
  2. Unacceptable?
  3. Why would someone get Haloes and Glare?
A
  1. Centered or Decentered while maintaining full limbal coverage
  2. Any area of limbus exposed; Crossing of limbus during the blink; and patient complaining of Halos and Glare
  3. Because OZD is not centered over the Pupil
40
Q

SCL Movement

  1. Promotes what?
  2. Quantified as change in what before and after a NORMAL Blink
A
  1. Post-lens tear film exchange

2. as the Vertical change in lens position

41
Q

Movement

  1. What is desired?
  2. What if there is no movement?
A
  1. 0.25-1 mm movement w/blink

2. No movement (+) push-up is okay.

42
Q

Excessive Lens movement

  1. What does excessive movement tell us about the CL?
  2. When is vision best?
    a. When is it worst?
  3. Doing Keratometry over a SCL will show what?
  4. Are Loose lenses comfortable
A
  1. Tells us there’s a LOOSE FIT
  2. Just before a Blink
    a. Just after
  3. Increased Distortion just after a blink
  4. Usually No
43
Q

Insufficient Lens movement

  1. Lack of movement indicates what?
  2. Vision before blink?
    a. Just after a blink?
  3. Doing keratometry over SCL will show what?
  4. Tight lenses: Comfortable?
A
  1. TIGHT Fit
  2. Slightly blurred
    a. Improves
  3. shows a DISTORTED Image that temporarily clears just after a blink
  4. YES. But they’re NOT HEALTHY!
44
Q

Lens movement over time

  1. Does a SCL act looser or tighter w/wear time?
    a. Why? (3)
A
  1. Acts Tighter w/time
    a. Post-lens Tear Film THINS; Material Dehydrates; Movement Slows
    * This is why it’s important to get a CL check appt.
45
Q

If a Lens Shows NO Movement

  1. What do we do?
A
  1. Push-up Test
    a. + Push up = okay to dispense lens.

Only indicated when movement is <0.25 mm to begin with

46
Q

Lens: Too Flat/Loose

  1. 5 Things that we see with it?
A
  1. Uncomfortable
  2. Excessive movement
  3. Papillary Reaction
  4. Decentration
  5. Can see Edge “stand off” or “fluting” (MORE COMMON in SiHy)
47
Q

Loose/Flat Lens

  1. How do we troubleshoot?
A
  1. Steepen BC and/or Increase Diameter
48
Q

Clinical Pearl

  1. A lens that appears to fit loose or flat could be what?
A
  1. Could be INSIDE OUT! (check for inversion of the lens)
49
Q

Excessive SCL Movement

  1. Deposited Lens
  2. Inverted Lens
  3. Flat Fitting Lens
A
  1. Replace Lens
  2. Educate Patient on Insertion
  3. Adjust Fit
50
Q

Too Steep/tight

  1. 4 things that we see
A
  1. Could be Comfortable
  2. Don’t judge a fit on patient comfort
  3. Insufficient/no movement
  4. Injection/Neovascularization
51
Q

Tight/Steep Lens

  1. 2 things to do to fix it
A
  1. Flatten BC and/or Decrease Diameter
52
Q

Initial Wearing Schedule

  1. When a patient is new to CLs, what do we do?
A
  1. Tell them to gradually increase wear time. (4+2 to 12) is the norm. (up to 16 is ok)

Contact Lens I Part 2 (5 decks)

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