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25 Cards in this Set
- Front
- Back
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5 reasons not fit a spherical RGP on a high astigmat? |
Increased 3 and 9 o’clock injection, poor lens positioning, visual complaints, corneal curvature changes, failure to correct residual astigmatism. |
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Name the 7 types of astigmatism. |
With-The-Rule, Against-The-Rule, Oblique, Irregular, Internal, Refractive, Residual
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In which form of astigmatism is the horizontal meridian the least curved (flattest) and the vertical meridian the most curved (steepest)? |
With-the-rule
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In which form of astigmatism is the horizontal meridian the most curved (steepest) and the vertical meridian the least curved (flattest)? |
Against-the-rule |
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What are the 3 common reasons for irregular astigmatism? |
keratoconus, trauma, Lasik |
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What can cause internal astigmatism? |
The toricity of the back surface of the cornea or the tilting of the crystalline lens with respect to the optic axis of the cornea. |
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What is another term for internal astigmatism? |
Lenticular astigmatism
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What is another term for refractive astigmatism? |
Total astigmatism |
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What is the astigmatism that is still present after a contact lens has been placed on the eye? |
Residual astigmatism |
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Name three types of toric RGP’s: |
Front surface toric, Back surface toric, Bitoric |
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What type of RGP lens is used when there is a small amount of corneal astigmatism but a large amount of total astigmatism? |
Front surface toric |
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What type of RGP is used when the refractive astigmatism is approximately 40% greater than the corneal astigmatism? |
Back surface toric |
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What type of RGP is used when there is a significant amount of corneal astigmatism (>3.00D)? |
Bitoric |
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What is the name of the bitoric lens guide? |
Ans. The Mandell-Moore Bitoric Lens Guide |
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What are the 3 most common modification procedures? |
Edge and surface polishing, Repowering, And flattening |
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What 4 types of tools are needed to modify an RGP? |
Box modification unit, suction cup, sponge tools, radius tools. |
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What type of polish can NOT be used? |
Silvo |
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Why not? |
It is ammonia-alcohol based, so it will ruin an RGP |
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Soft hydrophilic lenses are also known as: |
Hydrogels |
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What are the 6 main classifications of Hydrogel lenses? |
Daily wear, Extended Wear, Disposable, Tints, Torics, Bifocals. |
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What are the 3 main classifications of tinted Hydrogel lenses? |
Visibility, Enhancing, Opaque |
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What water content is best for the patient with dry eye? |
Low to medium |
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What 5 factors contraindicate hydrogel lens wear? |
Irregular corneas (Keratoconus), Radial keratotomy, Chronic allergies, Chronic antihistamine use, GPC |
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What is a standard rule-of-thumb for fitting hydrogels? |
Fit as flat as possible |
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What might you observe while using the biomicroscope if the lens is too tight? |
Conjunctival drag |
