Term
Coverage definitions of soft contact lenses Intracorneal <_____ Limbal ____ Paralimbal ____ |
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Definition
Intracorneal <12.5 mm Limbal 12.5-13.0 mm Paralimbal >13.5 mm |
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Term
| What type of fit is ideal for an SCL? |
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Definition
| Paralimbal because the lens extends out onto the sclera a little bit all the way around |
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Term
| How big are most corneas? How big are most soft contact lenses? |
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Definition
| Most corneas are 12 mm. Most soft contact lenses are 2 mm bigger, which is 14 mm. |
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Term
| What is the RA of a soft contact lens? |
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Definition
| RA of a soft lens is equal to the patients manifest astigmatism vertexed from the 12 mm spectacle plane to the cornea |
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Term
| How do you select the power for a soft contact lens on an astigmatic patient? |
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Definition
| Up to -1.00 D cylinder, you can use the spherical equivalent for a soft contact lens. |
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Term
| With what type of SCL would you expect to see astigmatism masked in the over refraction? |
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Definition
| the more stiff silicone hydrogels |
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Term
| What is the maximum amount of time you should wait for a lens to settle to evaluate the fit? |
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Definition
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Term
| Why don't we use fluroscein in fitting soft contact lenses? |
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Definition
| Fluroscein stains Soft contact lenses |
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Term
| What are the big three factors to remember in evaluating a soft contact lens fit? |
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Definition
CCM 1. Centration 2. Coverage 3. Movement |
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Term
| Slight decentration of a soft contact lens is ok as long as there is adequate _____. |
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Definition
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Term
| What do you call lens movement when the patient looks away from straight ahead gaze? |
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Definition
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Term
| What BC should you use for a soft contact lens? |
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Definition
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Term
| How much would you expect a soft contact lense to move with a blink in primary gaze? In nasal, temporal or upgaze? |
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Definition
0.25-1.0 mm slightly more than 0.25-1.0 mm because of the lid lag |
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Term
| What is the push up test? |
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Definition
Have the patient look up. Nudge the bottom of the lens If the lens moves with difficulty, the lens is too tight. If the lens moves easily the lens is fitting right.
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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 |
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Definition
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Term
| Most corneas have ___mm HVID. |
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Definition
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Term
| What type of lenses are all originally uncomfortable? |
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Definition
Both intracorneal RGPs and intracorneal soft lenses |
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Term
| What will keratometry mires look like if a lens is fitting to steep? |
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Definition
| The lens will be smooth immediately after the blink but will wrinkle up as the lens buckles and lifts off the cornea |
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Term
| What do the keratometry mires look like if a lens is fitting too loosely? |
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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. |
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Term
How does an inside out lens fit the cornea if it fits properly when right side out? |
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Definition
| too loose, keratometry mires initially wrinkled and later they settle and smooth before the next blink |
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Term
| What are three things you should always check? |
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Definition
1. Physical fit 2. coverage 3. quality of vison |
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Term
| Do low or high water have crisper optics? |
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Definition
| low water because they have more plastic |
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Term
| Do high or low water contact soft contact lenses have better quality of vision? |
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Definition
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Term
| Thick lenses dehydrate _____ than thin lenses. |
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Definition
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Term
| High water content lenses dehydrate ____ than low water content lenses and steal water from the tear film. |
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Definition
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