Test that measures the quality of tears - ANS B.U.T. Test (Break up time)
What is the O2 Permeability - ANS DK values of a lens
What are the disadvantages of Soft Lenses? - ANS Doesn't correct irregular
astigmatism, favors deposit formation
Which test measures the quantity of tears? - ANS The Schirmer test.
What are good results for the Schirmer test? - ANS 15 mm in 5 minutes.
What are dry eye results for the Schirmer test? - ANS 5-10 mm in 5 minutes.
Neovascularization is mainly due to what? - ANS Hypoxia, corneal edema, tight contact
lens fit
The Radii and Power of an average cornea - ANS 7.85 mm or 43.00 D
What are the layers of the cornea? - ANS Epithelium, Bowman's membrane, Stroma,
Descemet's membrane, Endothelium
The main disadvantage of soft contact lenses - ANS Protein deposits
What is it called when contact lenses are used to correct high myopia? - ANS
Orthokeratology (Ortho-K)
A contact lens with diameter that is larger than the cornea is a hydrophobic or
hydrophilic lens? - ANS Hydrophilic lens
Which of the following curves indicates the flattest base curve:7.50 mm, 37.50 D, 8.60
mm, 49.00 D? - ANS 37.50 D
A CTL was ordered with a BC of 7.85 mm but was received from the lab with a BC of
7.80 mm. The BC of the actual lens is _____. - ANS .25 D steeper than the ordered
CTL.
, A CTL with a BC of 7.42 mm is fitting too, a tighter fit may be achieved by changing the
base curve to: 7.46 , 7.85 mm, 8.04 mm, none of these? - ANS none of these... S.S.S.
rule
A CTL has a BC of 7.50 mm, what would the PPC most likely be? 7.45 mm, 42.50 D,
7.35 mm, 30.00 D - ANS 30.00 D= 11.25 mm/S.S.S. Rule
What does the term haptic Lens refer to? - ANS A scleral CTL size
The secondary curve of a RGP CTL is generally flatter or steeper than the CPC and by
how much? - ANS flatter by 2-4 diopters
When the power of a curve changes by 0.50 D, the radius of curvature changes by
approximately how much? - ANS 0.10 mm
When the CPC of a CTL measures 7.5 mm radius, how much is the power in diopters? -
ANS 45.00 D
A soft CTL demonstrates excessive movement. This can be fixed with a lens that has a
_________ diameter. - ANS Larger Diameter. (larger diameter-steeper fit=tighter fit)
HEMA is an abbreviation commonly used to describe what lens? - ANS The
chemicalname for soft CTL
What is the main reason to utilize a ballasted CTL? - ANS To have less rotation of the
CTL (Usually used in bifocal CTL's).
The Central portion of the back surface of the CTL is called _________. - ANS CPC
(Central posterior curve) or the Base Curve (BC) or the optic zone.
The distance between a flat surface and the back surface of the central portion of the
lens is called the ____________. - ANS Sagital depth (vault, height)
A loose fitting CTL can be made to fit tighter by ____________ the radius of the CPC. -
ANS shortening the radius of the CPC. S.S.S. Rule
What is an example of a hydrophilic lens material? - ANS HEMA
A contact lens in which the anterior surface contains two different radii of curvature and
the posterior surface is spherical is called a __________. - ANS front surface toric.
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