Term
| 2 countries where RGPs were popular |
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Definition
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Term
| RGP flexure increases when... |
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Definition
| peripheral cornea is steep, high Dk |
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Term
| one complication if a px who has been wearing PMMA is refitted with Hydrogels |
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Definition
| Corneal Exhaustion syndrome |
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Term
| 3 & 9 O clock staining seen in RGPs that are too flat/steep? |
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Definition
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Term
| RGP classification: Group 1 - 4 |
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Definition
1: MMA -Si - F
2: MMA +si - F
3: MMA + s + f
4: MMA - S + F |
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Term
| Advantages of Aspheric RGPs |
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Definition
| more tear exchange, less flare as no distinct zones, increased lens binding, mask up to 2Dc of corneal astig in asian, -3Dc in caucasians |
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Term
| 0.1mm change in BC of RGP = ___ change in power |
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Definition
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Term
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Definition
| corneal astig >0.40mm (2Dc) |
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Term
| in RGP alignment fit, the tear lens should be ____D? |
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Definition
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Term
| what % of water do RGP materials absorb? |
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Definition
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Term
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Definition
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Term
| Silicone and fluorine in RGP polymer give what characteristics? |
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Definition
Si: more oxygen permeability, poor wettability, protein deposits
F: good oxygen permeability, wets well, deposit resistance |
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Term
| Problems with Silicone Acrylate GP lenses 3 |
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Definition
| protein deposits, 3&9 o clock staining, pappilary conjunctivitis |
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Term
| Fluorosilicone acrylates: problems |
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Definition
| lens binding, lipid deposits in some px |
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Term
| Fluorosilicone acrylates: advantages |
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Definition
| good oxygen permeability, good deposit resistance --> low CLPC, wettable |
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Term
| what material to use to solve 3-9oclock staining and CLPC? |
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Definition
| CAB cellulose acetate butylate |
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Term
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Definition
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Term
| why is edge clearance needed? 3 reasons |
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Definition
| tear exchange, more comfortable and less distortion, aid removal |
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Term
| Increasing diameter of RGP will |
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Definition
| increase comfort as edge slips under lid, but lens may extend beyond limbus in blinks |
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Term
| problems with high Dk lenses? 2 |
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Definition
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Term
7.85:7.80 / 8.65: 8.80 / 10.00:9.30
how many curve design is this lens?
what does 7.85 refer to?
what does 8.80 refer to? |
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Definition
| tricurve; BC 7.85; 8.80 is diameter of curve 1 |
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Term
| what manufacture method gives good blink induced movement? |
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Definition
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Term
| Push up 0 - 100. which is tight? which is loose |
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Definition
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Term
| 3 method for measuring oxygen transmissibility of a lens. which is most accurate for high Dk lenses |
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Definition
| coulometric, polarographic; coulometric |
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Term
| 3 in vivo methods of measuring wetting angle |
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Definition
| sessile drop, wilhermy plate, captive bubble. |
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Term
| FDA classification: Grp 1 -4 means Watercontent/ionic? |
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Definition
1: non ionic, low water
2: non ionic, high water
3: ionic, low water
4: ionic, high water |
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Term
| Adv and disadv of ionic vs nonionic materials |
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Definition
| ionic: more wettable, more protein deposits |
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Term
| rank lens manufacture methods )spin cast, lathe cut, cast moulded) according to lens movement on eye - most movement to least: |
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Definition
| lathe cut > spin cast > cast moulded |
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