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OPT 2500 ( FULL OVERVIEW ) > UNIT SIX - Soft Lens Design And Selection > Flashcards

UNIT SIX - Soft Lens Design And Selection Flashcards

1
Q

What are some of the soft lens advantages?

A 
Initial comfort 
Rapid adaption
Intermittent wear 
Minimal lens loss
Less flare
Great cosmetic lens
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2
Q

What are some of the disadvantages with soft lenses ?

A 
Spherical lenses provide no correction for corneal astigmatism 
Lack of durability 
Deposits
Lens disinfection
Less control of lens parameters
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3
Q

What does this image show ?

A

Soft lens deposits

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4
Q

What does this image show?

A

Discoloration of soft lenses

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5
Q

What does this image show?

A

Soft lens tear with fungus

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6
Q

What are the 6 soft lens performance factors ?

A

1) Oxygen transmission DK/L
2) Durability
3) Water content
4) Composition
5) Flexibility/Drape
6) Thickness

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7
Q

What does the acronym DK/L for oxygen transmission mean?

A

DK: Increases with water content
L: (Thickness) transmission doubles if thickness is reduced by 50%

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8
Q

What happens to durability if water content increases ?

A

It decreases

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9
Q

What happens to durability when thickness decreases?

A

It decreases

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10
Q

What is the water content range for soft lenses ?

A

25-85%

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11
Q

What are the high and low percentages of water content according to the FDA?

A

High: more than 50%
Low: less than 50%

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12
Q

What size are the pore on soft lenses when the water content is lowered?

A

They are smaller

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13
Q

Lower water content allows less or more enzyme absorption?

A

Less

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14
Q

What are some characteristics of higher water content lenses ?

A

Increased deposit problems and greater parameter changes.

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15
Q

What does ionic mean?

A

Negative surface charge attracts positively charged protein.

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16
Q

What does non-ionic mean?

A

Less reactive surface, less deposits

17
Q

As water content increases, flexibility

A

Increases

18
Q

As thickness decreases, flexibility

A

Increases

19
Q

What are characteristics of thinner lenses ?

A 
Increase oxygen thickness 
Contour to the eye
Move less 
Fit tighter
Increase initial comfort 
Dehydrate quicker in a dry environment 
Be more difficult to handle 
Not mask corneal astigmatism 
Damage more easily
20
Q

What are some goals for soft lens design?

A

Full corneal coverage
Three point touch
Stable acuity
Comfort

21
Q

What are three things apart of the initial lens selection process?

A

2mm greater than corneal diameter (HVID)
Lens power
Wearing and replacement schedule

22
Q

What are the three steps to calculate the power of soft lenses?

A

1) transpose to - cyl
2) if cyl is 0.50D or greater, determine spherical equivalent. (1/2 cyl + sph)
3) compensate for vertex distance if the S.E. Power is greater than +/- 4.00D

23
Q

What do we see in a well fit soft lens?

A

Good centralization/ full corneal coverage
0.5-1.0mm movement
Easy movement with glide or push up test
Stable keratometer mires, VA, and retinoscopy reflex
Good comfort

24
Q

What do we see in a poor fit soft lens?

A

Poor centralization
Excessive movement with Glide or push up test
Keratometer mires, VA and retinoscopy reflex clear but blur immediately after blink
Poor comfort
Edge stand off

25
Q

What do we see in a tightly fit soft lens?

A

Minimal or no movement
Slight movement with glide or push up test.
Keratometer mires,VA and retinoscopy reflex blurry but clear immediately after blink.
Good initial comfort
Circumcorneal injection and indentation

26
Q

How to solve for a soft lens that is too tight?

A

Select a smaller diameter or flatter base curve

27
Q

How to solve for a soft lens that has poor centralization?

A

Larger diameter, thinner or steeper base curve

28
Q

How to solve for a dehydrated soft lens?

A

Thick or lower water content

29
Q

How to solve for poor vision in a soft lens?

A

Improve the fit and check for residual astigmatism

OPT 2500 ( FULL OVERVIEW ) (7 decks)

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