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27 Cards in this Set
- Front
- Back
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True or False? If a stock lens is available, it is normally used instead of a custom surfaced lens.
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True
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For a high plus lens powers, as center thickness increases. what is true.
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Magnification of the wearer's eye increases.
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Given the generalized formula for MBS, what is the MBS required for a frame having an effective diameter of 53 and a decentration of 3mm per lens when no allowance is made for chipping?
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59 mm
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when is it critical that the smallest possible lens blank be used?
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when the prescription is plus in power.
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internal lens deficiencies are inspected for what 2 ways?
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1. Observing a straight line through the lens as the lens is moved back and forth.
2. Looking through the lens at a black background under indirect illumination |
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A priscription is -2.00-1.25 x 030. what are the two power wheel readings that appear when first spear then cylinder lines are brought into focus?
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-2.00, and -3.25
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lenses should never be placed convex side down on a job tray.
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lenses should be placed concave side down and convex side up on a job tray.
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what should always appear either exactly in front of or somewhat below the wearers pupil
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MRP
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the distance power for a progressive addition lens is verified at the
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PRP: prism reference point
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The effective diameter (ED), of a lens shape
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Twice the longest radius of a lens shape as measured from the boxing center.
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the angle of ED is measured as
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The angle from the 180-degree line to the ED line, measured counterclockwise for the right eye.
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what is the point on a pattern around which it always rotates
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Mechanical center
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true of false ?
cutting center mechanical center edging center all mean the same |
true
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frame difference formula
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A-B
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True of False? using the same pattern for frames having two different sizes means that the frame size and the frames lens shape may e altered somewhat
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true
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A pattern has a frame difference of 10. A 50mm eyesize frame of the same shape has a B dimension of 40. What is the B dimension if an identically shaped frame has a 55mm eyesize?
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45 mm
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A frame has a B dimension of 40mm. IF the segment hight of the lens is 17mm, what is the segment drop? (segment drop will be listed as a negative number because it is below the midline of the lens.
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remember 40/2 =20- 17= -3
so the answer is -3 |
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A pattern is marked with a frame difference of 7mm. If the lens eyesize is 50 mm and the segment height is to be 19mm which of the following indicates the segment drop?
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50-7=43/2=21.5-19= -2.5
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A pattern has a pattern difference of 7. what is the segment drop for a frame with an A dimension of 52 and segment height of 17mm?
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52-7=45/2=22.5-17= -5.5
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if a pattern center is displaced too far nasally which direction must the lens be decentered to compensate for the error
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temporally
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7 steps of surfacing
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data entry
layout blocking generating fining polishing quality control |
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MBS for grinding with prism for decentration and or fininshing MBS formula
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ED + 2 (dec) +2
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MBS with out grinding for prism and or a semifinished lens formula
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ED+2(0)+2=
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off center blocking formula
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A+DBL minus patients Pd divided by 2 = decentration
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on center blocking formula
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A + DBL = frame pd
frame pd - patients PD divided by 2= decentration prism = .decentration(patient prescription powerD) |
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If the segment height is 20 mm, what is the segment drop or raise with reference to the horizontal mid-line for a frame with the following dimensions.
A=42 B=38 DBL=16 |
+1 mm (raise)
because 38/2=19 and 19 +1 =20 |
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which of the choices describes the segment inset for the following frame and PD measurements?
frame:A=5 B=44 DBL=17 PD=64/61 |
1.5 mm
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