Term
| What increases as the contact lens curvature more closely matches the corneal cuvature? |
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Definition
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Term
| What term is used for lenses that are not too flat or steep and have a maximum amount of capillary attraction? |
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Definition
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Term
| What parameters can be modified on a tricurve lens? |
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Definition
1) size of curves 2) blending of curves 3) diamter of lens 4) optic zone diamter |
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Term
| How much do you need to change the BC to get a significant change in alignment? |
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Definition
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Term
| A ____ sag depth will fit more tightly, while a _____ sag depth will fit more loosely. |
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Definition
deeper (larger) shallower (smaller) |
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Term
| An increased optic zone diameter means an _____ sag depth and hence a ____ fit. |
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Definition
increased sag depth tighter fit |
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Term
| If we make the OZD larger, we must make the BC ____ to compensate. |
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Definition
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Term
| 0.4 mm smaller OZD=_____mm or ____D steeper BC to compensate |
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Definition
| 0.4 mm smaller OZD=0.05 mm or 0.25 D steeper BC |
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Term
| _____ edge lift to increase lid attachment, ______ edge lift to decrease lid attachment. |
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Definition
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Term
| Steepen the secondary and tertiary curves by ____mm to decrease the edge lift by ____mm. _____ the secondary and tertiary curves to increase the edge lift. |
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Definition
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Term
| Dessication occurs when the edge lift is too ____, whereas chafing occurs when the edge lift is too ____. |
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Definition
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Term
| What is the definition of a plus contact lense? |
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Definition
| Any lense with that is thicker at the center than the periphery. This includes all lenses more plus than -1.00 D. |
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Term
| What property of a contact lense causes a -1.00 D lense to take on a plus shape? |
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Definition
A low minus lense starts its life out thicker in the periphery than the center, but by the time the peripheral curves are added, the lens becomes thinner in the periphery than the center |
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Term
| The melon seed effect means that a ____ edge slips out easily from under the lid. |
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Definition
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Term
| How high a lens power necessitates a minus carrier? |
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Definition
| +2.00, anything less and a regular carrier with a parallel periphery will do |
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Term
| Above what minus power necessitates a plus carrier? |
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Definition
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Term
| A higher Dk material must be made ____ than a lower Dk material due to flexure concerns. |
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Definition
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Term
| ____ ___ is caused by reflections from the peripheral cornea and the tear meniscus. ___ _____ is usually not a problem unless the edge of the optic zone is close to the ____. |
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Definition
Lens flare Lens flare pupil |
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Term
| How are centration and lid attachment opposing forces? |
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Definition
| A large lens centers well without the lid, but the lid attaches well to a large lens which causes it to decenter |
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Term
| What are the six parameter change criteria in order? |
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Definition
1. Base curve 2. Lens diameter 3. Lenticular (if you have already) 4. Peripheral curve radii (edge lift) 5. Material (specific gravity) 6. Center thickness |
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