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Unit 7 > unit 7 > Flashcards

unit 7 Flashcards

1
Q

How to Order Eyeglasses

A
  • Figuring the frame and the lens type are the first steps
  • Once you are finished with the measurements and the payment then you have to start the process of ordering the glasses.
  • Step one
  • Make sure all information is present and correct!
  • Patients prescription
  • Patients measurements
  • Patients lens choices including style and coatings
  • A,B,ED, DBL, Frame Model, Size and Color, Bevel type
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2
Q

Lens Centration

A

DBC = A + DBL (Frame PD)
DBC – wearer PD = Decentration per lens
2

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3
Q

Monocular PD

A

Decentration=DBC/2 -monocular PD

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4
Q

Vertical Decentration (usually a higher number)

A

Vertical Decentration=OC Height- B/2

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5
Q

Minimum Blank Size

A

MBS=ED+2(per-lens decentration)+2 mm

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6
Q

What does decentration mean?

A

When an optical center of a lens is moved away from its expected position in front of the eye, that lens now causes a prismatic effect.

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7
Q

Bevel allowance?

A

The piece that sticks out of the machine to stick onto the frame

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8
Q

Spotting the lens

A
  • Step 1: Dial the desired axis for the prescription
  • Step 2: Dial the Sphere of the prescription
  • Step 3: Put the lens in and turn lens until the sphere lines are clear and unbroken
  • Step 4: Verify prescription and center the lens
  • Step 5: Spot the lens
    95% of edging mistakes start here!
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9
Q

Trace the frame

A
  • Metal and Plastic frames are traced in the same manner. (This is what we do with our Essilor machines)
  • They are both placed face down in the tracer and centered with no lenses
  • Once the frame is centered you can press start to trace the frame
  • The frame trace should be the same as the frame shape itself, you may want to double check this.
  • Then you would enter the patients OC and PD measurements for each lens.
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10
Q

Frame Patterns

A

Some offices have an older patterned edging system
* Patterns might be sent with the frames when ordering or…
* Patterns might have to be made by hand..

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11
Q

Putting the frame in the tracer

A

Place the frame face down in the tracer between the black clamps and close the silver handle to cradle the frame on both sides
Try to line up the DBL on both sides as equally as you can.
Is it the correct shape?
* Take a look on the screen of the tracer, is it the correct shape to your frame that you are edging lenses

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12
Q

Blocking the Lens

A
  • Once the lens has been spotted and the frame has been traced then it is time to block the right lens
  • You line the center spot to the markings provided on the blocking device with the proper decentration
  • The you align the outer two markings with the corresponding horizontal line as the center dot to align the axis of the lens
  • This is the second most common area where mistakes happen!
  • Apply the blocking pad stickers and any additional stickers to the chuck
  • Then you press the button or move the arm to attach the chuck to the lens.
  • Move to the left lens and repeat the steps.
  • Start with the right lens!
  • Place the O.D. lens in the blocking area of the tracer.
  • If the lens is slipping or too large or small for the prongs inside you can adjust or switch it out for the
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13
Q

Your lens is ready for the chuck

A
  • Once you have entered your patient measurements to the tracer and placed your lens in the blocking area you will line up your dots with the ones given on the screen.
  • Now what?
    select the material on the tracer
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14
Q
  • Answer all the questions (??) the tracer is asking you.
A

◦ Material type
◦ 1 star or two
◦ Bevel type
◦ Edge polish
◦ Front safety bevel
◦ Back safety bevel and how much
Cycle type
Type of finish
Polishing
Front side safety bevel (chamfering)
Rear surface beveling

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15
Q

Edging the lens (putting the lens in the edger)

A
  • There is a magnet that will help the lens stay in the prongs of the turning rods.
  • The rods prongs may need to be changed to match the size of the chuck needed.
  • Be mindful not to touch the backside of the lens.
  • Once you have finished selecting all your settings and blocked your lens it is now time to edge it.
  • Is the lens in your edger?
  • Bring over the pattern by touching the tracer looking button on the edger.
  • Double check the lens shape and the settings for accuracy
  • Press the green “play” arrow button to start the edging process.
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16
Q

Lens Insertion

A
  • Once the lens is cut it is important to check the sizing.
  • If a lens is too big now is the time to bring it down. The lens size will default to the OS lens.
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17
Q

Final Inspection

A

Frame and lens inspection
◦ Start with the lens inspection and verification
 Are there any scratches, pits or coating defects?
 Is the lens inserted properly?
 Does the prescription match? (More on this next slide)

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18
Q

◦ Frame inspection

A

 Is the frame in good shape?
 Does the frame have any scratches or defects?
 Does the frame need to be put back into standard alignment?

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19
Q

Verification

A
  • Does the prescription match?
    ◦ For this you will need the tolerance chart
    ◦ Does the sphere match?
    ◦ Does the Cyl match?
    ◦ Does the axis match?
    ◦ Does the MRP match?
    ◦ IF NOT, see tolerance chart!
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20
Q
  • The Higher the Abbe value…
A

the less chromatic aberration present in the lens.

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20
Q
  • The Higher the Abbe value…
A

the less chromatic aberration present in the lens.

21
Q

Polycarbonate - RI & AV

A

RI; 1.586

22
Q

Lens Measurements

A
  • PD
  • Ocular Centre Height
  • Segment Height
  • Vertex
  • Wrap also known as face form
  • Pantoscopic Tilt
23
Q

Pupillary Distance

A

the distance from one pupil

24
Q

effect on vision if PD is misread

A

-If PD is off it is creating prism effect

25
Q
  • How about high wrap frames?
A

-high wrap can affect the PD

26
Q

OC for trifocal

A

halfway through the iris

27
Q

OC of single vision

A

the center of the pupil

28
Q

OC for bifocal

A

the bottom lid line

29
Q

is posture or height important for OC

A

it is important for them to be relaxed and at their comfortable seating position

30
Q

how do we measure frame wrap

A

From the piece of paper or the electronic one

31
Q

why is frame wrap relevant

A

It can affect the PD, and the movement of the eyeball

32
Q
  • What are the repercussions if frame wrap is done wrong?
A

It will create more cylinder in the lens

33
Q

how do we measure pantascopic tild

A

on patients face

34
Q
  • Why is pantascopic tilt relevant?
A

Movement of the eyeball downwards

35
Q
  • What are the repercussions if pantascopic tilt is done wrong?
A

It will create more cylinder in the lens

36
Q

how to measure vertex distance

A

distometer

37
Q
  • Importance of vertex distance
A

The power of the distance from the lens to the eye

38
Q

difference between effective and compensated powers

A
  • Effective (power that the lens is going to feel like to the patient at that vertex distance) and compensated powers (power we are going to order from the lab) description
39
Q

important to know .

A
  • When the lens moves AWAY from the eye or CLOSER to the eye we need a new power.
  • Plus lenses that move away from the eye need a weaker lens
  • Minus lenses that move away from the eye need a stronger lens
40
Q
  • Effective power formula
A

De=Dl/(1+dDl)

41
Q
  • Compensated power formula
A

Dc=Dl/(1-dDl)

42
Q

what the things stand for in formula

A
  • Where De is the effective power of the lens
  • Where Dc is the compensated power of the lens
  • Where Dl is the lens power(actual)
  • Where d is the change of vertex distance in METERS
43
Q

how to measure base curve

A

lens clock

44
Q
  • Why is it base cruve important
A

Tells you prescription on this axis, figuring out what lens to order from the lab

45
Q

what is the positve and negative for base curve

A
  • Positive base curve is front surface
  • Negative base curve is back surface
46
Q

lens thickness on a minus lens

A

thinnest point is the center
thickest is the edges

47
Q

lens thickness on plus lens

A

thinnest point is edges
thickest is center

48
Q

CSA level of standard for basic impact materials

A
  • the thickness minimum must be met at 3.0mm
  • Withstand the impact of a 5/8” steel ball dropped from 50”
  • Must be marked with the Manufacturers’ logo or identifying mark
49
Q

CSA level of standards for high impact materials

A
  • The thickness minimum must be met at 2.0mm
  • High Velocity Impact Test – Lens is mounted on a special holder, must be capable of withstanding the force of a ¼” travelling at 150 feet/second
50
Q

CSA approved level of standara for safety glasses

A
  • Anti-Reflection Coatings generally reduce the impact resistance of a lens to the same lens in an uncoated state.
  • Should not be used in industrial or sports eye protectors at 2mm center thickness where there is a high-risk exposure to high energy impacts.

Unit 7 (1 decks)

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