Shared Flashcard Set

Details

Opt 225 Contact lens
Test 2 fitting scl
26
Other
03/16/2008

Additional Other Flashcards

 


 

Cards

Term

Coverage definitions of soft contact lenses

Intracorneal <_____

Limbal ____

Paralimbal ____

Definition

Intracorneal <12.5 mm

Limbal 12.5-13.0 mm

Paralimbal >13.5 mm 

Term
What type of fit is ideal for an SCL?
Definition
Paralimbal because the lens extends out onto the sclera a little bit all the way around
Term
How big are most corneas?  How big are most soft contact lenses?
Definition
Most corneas are 12 mm.  Most soft contact lenses are 2 mm bigger, which is 14 mm.
Term
What is the RA of a soft contact lens?
Definition
RA of a soft lens is equal to the patients manifest astigmatism vertexed from the 12 mm spectacle plane to the cornea
Term
How do you select the power for a soft contact lens on an astigmatic patient?
Definition
Up to -1.00 D cylinder, you can use the spherical equivalent for a soft contact lens.
Term
With what type of SCL would you expect to see astigmatism masked in the over refraction?
Definition
the more stiff silicone hydrogels
Term
What is the maximum amount of time you should wait for a lens to settle to evaluate the fit?
Definition
5 minutes
Term
Why don't we use fluroscein in fitting soft contact lenses?
Definition
Fluroscein stains Soft contact lenses
Term
What are the big three factors to remember in evaluating a soft contact lens fit?
Definition

CCM

1.  Centration

2.  Coverage

3.  Movement

Term
Slight decentration of a soft contact lens is ok as long as there is adequate _____.
Definition
coverage
Term
What do you call lens movement when the patient looks away from straight ahead gaze?
Definition
lens lag
Term
What BC should you use for a soft contact lens?
Definition
4 D flatter than K
Term
How much would you expect a soft contact lense to move with a blink in primary gaze?  In nasal, temporal or upgaze?
Definition

0.25-1.0 mm

slightly more than 0.25-1.0 mm because of the lid lag

Term
What is the push up test?
Definition
  1. Have the patient look up. 
  2. Nudge the bottom of the lens
  3. If the lens moves with difficulty, the lens is too tight. 
  4. If the lens moves easily the lens is fitting right.
Term
For every 0.4 mm increase in diameter, you must decrease the BC ____.  For soft lenses this works out to about __D ____ than K
Definition

0.25 D

4 D

flatter

Term
Most corneas have ___mm HVID.
Definition
12 mm
Term
What type of lenses are all originally uncomfortable?
Definition

Both intracorneal RGPs and intracorneal soft lenses

Term
What will keratometry mires look like if a lens is fitting to steep?
Definition
The lens will be smooth immediately after the blink but will wrinkle up as the lens buckles and lifts off the cornea
Term
What do the keratometry mires look like if a lens is fitting too loosely?
Definition
Right after the blink, the mires will be wrinkled.  After time passes the mires will appear more clear as the lens settles prior to the next blink.
Term

How does an inside out lens fit the cornea if it fits properly when right side out?

Definition
too loose, keratometry mires initially wrinkled and later they settle and smooth before the next blink
Term
What are three things you should always check?
Definition

1.  Physical fit

2.  coverage

3.  quality of vison

Term
Do low or high water have crisper optics?
Definition
low water because they have more plastic
Term
Do high or low water contact soft contact lenses have better quality of vision?
Definition
high water, slightly
Term
Thick lenses dehydrate _____ than thin lenses.
Definition
slower
Term
High water content lenses dehydrate ____ than low water content lenses and steal water from the tear film.
Definition
slower
Term
Definition