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Ophthalmic Optics Block 10 > Lesson 8 > Flashcards

Lesson 8 Flashcards

1
Q

Helps reduce the chance of damaging delicate frames

A

Frame adjustment pliers

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2
Q

Holds lens and screw when bending temples or bridge area

A

Rimless mounting adjustment pliers

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3
Q

Designed to easily and safely remove compression mounted hardware

A

Compression hardware removal plier

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4
Q

Designed to trim of extra plastic blushing material before mounting

A

Sleeve trimming plier

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5
Q

Designed for easy assembly of single or double leg compression mounted frames

A

Compression plier

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6
Q

What is a thumbtack useful for when adjusting frames

A
  • aligning the barrels of a spring-hinged temple
  • removing bottom nylon cord from a semi-rimless frame
  • removing top cord from semi rimless frame
  • assembling a rimless compression mount frame
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7
Q

Lens bulge is the same as the _________

A

Sag of the front surface

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8
Q

Vertex depth is the same as the ______

A

Sag of the back surface

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9
Q 
Calculating edge thickness for decerneted lens 
A=48mm
DBL=16mm
PD=25/25
N-1.6
CT=1mm
Rx=-4.00D
A

48+16=64
Half of that is 32 (mono frame PD)
32-25=7mm decentration

48/2=24=24
24+7=31=h

  • 4(31^2)/(2000(1.6-1)
    3. 20mm+1=4.20mm
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10
Q

A lens clock calibrated for n=1.523 is placed on a surface with a refractive index of 1.8. If the clock reads +8.00, what is the true power of the surface

A

(1. 8-1/1.523-1)x8

- 12.24

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11
Q

When finding net prism what do you do

A

Take the difference

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12
Q

When asked to add the prism what do you do

A

Pythagorean theorem or add them together if they are the same

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13
Q

Prism thickness

A

(Zh)/(100(n-1))

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14
Q

Using thickness difference to determine prism power

A

Z=(100t(n-1))/h

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15
Q

Inducing a vertical prismatic effect in the lower half of one leans to correct vertical imbalance

A

Slab-off

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16
Q

Induces BU prism in the most minus lens in the vertical meridian in order to offset excessive base down prism induced by the opposite lens

A

Slab off

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17
Q

Provides BD prism so it is always used in the most plus lens int he vertical meridian in order to offset excessive BU prism induced by the opposite lens

A

Reverse slab off

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18
Q

When using slab off

A

Higher minus
Lowest plus
The minus lens

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19
Q

When using reverse slab

A

Lowest minus
Highest plus
The plus lens

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20
Q

When is slab off used the most

A

Lined bifocals

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21
Q

How can you correct vertical imbalance

A
  • Slab off
  • Dissimilar segs (place OC of the right and left segs at different positions)
  • multiple specs
  • contact lenses
  • fresnel prism
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22
Q

The sudden displacement of an image at the bifocal line

A

Image jump

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23
Q

Calculating image jump

A

Independent of distance power and seg location, just depends on add power and shape of seg

24
Q

Calculate image jump

  • Rx: +2.00-1.25x180 +2.00D
  • seg drop=4mm
  • seg=flat top 28 (the seg OC is 5mm from the distance)
A

5mmx2.00/10=1D BD image jump

25
Calculate image jump - 30mm round seg - Rx: +2.00-1.00x180 +2.00D
30/2=15mm 15x2/10 3BD
26
Mag/min and plus lens
Plus lens creates magnification, a larger than normal retinal image
27
Minus lenses and mag/min
Create minification, smaller than normal retinal image
28
Lenses and mag
All lenses produce magnification
29
What happens to mag/min if you increase the power
It also increases
30
Greater vertex distance and mag
Increases it
31
Describes the ratio of image height to object height
Lateral magnification
32
Ratio of the angle subtended by the image produced by an optical system
Angular magnification
33
The ratio in image size for a spectacle lens corrected eye compared with the size of the image for the uncorrected eye, impacted by power of the lens and its shape
Spectacle magnification SM=Ig/Io Ig=retinal image size with glasses Io=without glasses
34
What elements contribute to spectacle magnification
Power factor | Shape factor
35
A component of spectacle magnification that is determined by the back vertex power and the vertex distance of the lens
Power factor in spectacle magnification 1+dPv
36
Power factor for hyperope
Always >1
37
Power factor for mope
Always<1
38
A component of spectacle magnification that is determined by the base curve and the thickness of the lens
Shape factor 1+(t/n)P1
39
For a meniscus lens, the shape factor
Is always >1
40
To find spectacle magnification
Add shape factor and power factor SM=Mp+Ms
41
Lens is thick and BC is steep, so increases one or the other will have a meaningful effect on shape factor
Hyperope
42
Lens is thin and BC is flat, so in order to have a meaningful effect not he shape factor, both lens thickness and drop surface power must be increases
Myope
43
Binocular condition in which the apparent sizes of the images seen with the two eyes is unequal
Aniseikonia
44
Lenses for aniseikonia
Lens design is not intended to remove magnification or exactly match magnification from each lens. It decreases the magnification difference so that binocular vision is restored Called Iseikonic lenses
45
Variables that can be changed to reduce magnification
Base curve Center thickness Index refraction Vertex distance CANNOT CHANGE POWER
46
Left and right eyes produce equally sized images on the retina
Iseikonia
47
Iseikonic lenses
Custom designed lenses that use the optimal curvature, thickness, and index of a given prescription combination to balance the magnification
48
Occurs with specular, not diffuse, reflections
Polarization
49
The angle of incidence at which reflected light from a refracting surface is completely polarized
Brewsters angle
50
What are the 2 axis for polriazwtion
Absorption axis | Transmission axis
51
Where is a absorption axis in a polarixaed lens
Horizontal
52
Where is the transmission axis on polarized lenses
Vertically
53
A thin film made by taking polyvinyl acetate (PVA) film, stretching it to five times its normal length and dipping it in iodine. Polarization is caused by absorption of iodine between the chains of PVA molecules
Polaroids
54
When switching from front to back surface, why does the axis change and how much
Mirror image
55
What kind of refractive index is thinner in higher RX?
Higher
56
As RI increases, what happens to abbe
Decreases

Ophthalmic Optics Block 10 (4 decks)

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