1155 Flashcards
Using the nominal lens power formula, calculate the total Lena power having a front surface curve of +6.00 and a back surface curve of -3.00
D1+D2=D3
+3
What contribution did Ben Franklin give to the optical profession?
Invented bifocal lenses
The index of Refraction of crown glass is?
1.523
Define The nominal lens power formula
F1+F2=FTotal
Applying the concept of corrected curve lens theory, choose the best base curve for the following -6.00 -2.00 x 90 ASHPERIC LENSES
Sph. Equiv + 1/2 cyl divide by 2 + 6.00 -2.00D bc it’s a aspheric
+0.50
Point on a lens where light travels straight through
Optical center
An imaginary line perpendicular to lens surface
Principle axis
The point around which the lens is edged
Mechanical center
Columbia resins 39th formula is what we refer to as?
CR 39/ plastic
Applying the concept of corrected curve lens theory, choose the best base curve for the following +4.00 ASPHERICS
SPH EQUIV + 6.00 - 2.00
+8.00
Diverge light Virtual focus Thinner at center thicker at edges Minify image Shows with motion Are all characteristics of what lens?
Minus lens
Apply the concept of corrected curve lens theory, choose the best base curve for the following
-1.00 -6.00 x90
SPH.equiv + 1/2 cyl / 2 + 6.00
+4.00
Applying the concept of corrected curve lens theory choose the best base curve for
+6.00-2.00x90
SPH.equiv + 1/2 cyl + 6.00
+11.00
Spectacle lenses are prescribe for 4 reasons: refractive errors, faulty binocular vision, protection, and comfort. TRUE OR FALSE?
TRUE
Applying the concept of corrected curve lens theory, choose the best base curve for the following:
+1.00 SPH
SPH. Equiv + 6
+7.00
Converge light Thicker at center thinner at edges Shows against motion Effective power increases as the vertex distance increases Are for what lens ?
Plus lens
Applying the concept of corrected curve lens theory, choose the best base curve for the following
-1.00sph
SPH.equiv / 2 + 6.00
+5.50
Combining cross cylinders
Ex.) -1.25-0.37x180
Transpose, make an X, and rewrite the RX in crossed cylinder form
Ex.) -1.25-0.37x180
-1.62+0.37x90
Ans) is -1.25x90 -1.62x180
Combining cross cylinders and writing them and plus and minus cylinder
Ex.) +0.25+1.00x90 combine w/
-0.50+1.00x180
Transpose so both have same axis
Combine the spheres and cylinders algebraically keep same axis
Ex.) +1.25-1.00x180
-0.50+1.00x180
\+0.75 SPHIn labeling The optical cross for toric transposition the CC Is the strongest back curve the TBC is the weakest back curve and the BC is the base curve on F1 when the lens is minus cylinder design
TRUE OR FALSE?
True
Two ways a prism must be expressed in relationship to a prescription are:
Prism dioptric power, base direction
The direction of a the base direction for prisms is expressed in degrees from ?
0-360
When light strikes a prism it will deviate towards the ______ while the image will be displaced toward the _____.
Base/Apex
Excessive prism base down will cause the client to see
The floor appears as if concave
As if they are standing in a hole and walking uphill
Vertical objects as being taller then they are
Excessive prism base up will cause the client to see
The floor appearing convex
On top of the world
Walking downhill
Vertical objects appearing shorter then they are
What is the index of refraction for polycarbonate?
1.586
What is the index of refraction for CR-39
1.49
How many mm below for a Flat top?
5
How many mm below for a double d?
5 mm
How many mm below for a Flat top?
5
How many mm below for a double d?
5 mm
How many below for a round seg?
1/2 the diameter
How many below for an ultex a?
19mm
How many mm below for a ribbon seg?
1/2 the vertical
How many for an executive?
On seg line
