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OP2201- Dispensing > 2. Occupational Lenses > Flashcards

2. Occupational Lenses Flashcards

1
Q

What is an occupational multifocals?

A

Any lens chosen by careful thought and positioning for a specialized viewing situation is considered to be an occupational lens. i.e lens that is not considered for ‘general wear’.

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2
Q

Describe how double segment lenses are designed?

A

They have the segment in normal position + second segment at the top of the lens.

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3
Q

Who requires double segment lenses?

A

People that require intermediate or near when looking upwards- like plumbers, electricians, mechanics, librarians, pharmacists.

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4
Q

Double segments are separated by ?

A

14mm

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5
Q

What information is required before dispensing double segments?

A

Need to recreate px working environment

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6
Q

What is quadrafocal?

A

Trifocal with upside down segment at top

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7
Q

Limitations of progressive lenses?

A
  1. Distance portion lies straight ahead.
  2. If px is doing a lot of intermediate tasks.
  3. Intermediate portion has a narrow width.
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8
Q

Are standard progressive lenses useful for pxs doing a lot of near or intermediate work?

A

NO

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9
Q

Implications of excessive add in a lens?

A

More unwanted surface astigmatism

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10
Q

Implications of a small add power to move from intermediate to near?

A

Less unwanted surface astigmatism, longer wider progressive zone, less rapid transition to power.

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11
Q

What is taken as a reference point in typical progressive lenses vs typical degressive/ occupational lenses?

A

Reference point for typical progressive lenses: Distance Rx and the progressively add plus power.
Reference point for occupational lenses: Near is reference point and remove plus to get to intermediate.

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12
Q

10 general considerations when dispensing occupational lenses?

A
  1. Task size
  2. Working distance
  3. Size of occupational addition
  4. Whether task is still or moving
  5. Position of px and task
  6. Lighting
  7. Contrast
  8. Tints and colour accuracy
  9. Stereopsis
  10. Possibility of ocular hazard
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13
Q

Why is task size considered when dispensing occupational lenses?

A

Consider level of VA to be achieved and field of view - ask px to bring an example of what they need to see if its is specialized.

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14
Q

Why is working distance considered when dispensing occupational lenses?
How is it calculated?

A

Calculate range of clear vision to ensure no ‘gaps’ at required distances.
Calculation: (Max W.D= 1/ Add X 100cm)

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15
Q

Why is size of occupational addition considered when dispensing occupational lenses?

A

Related to task

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16
Q

Why is whether task is still or moving considered when dispensing occupational lenses?

A

Narrow optical areas limit eye movement

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17
Q

Why is lighting considered when dispensing occupational lenses?

A

Inverse square law- double the distance from source = 1/4 of light. Visual perform improves with lighting.

18
Q

Why is contrast considered when dispensing occupational lenses?

A

Higher contrast = improved visual performance

19
Q

Why is tints and colour accuracy considered when dispensing occupational lenses?

A

Colour accuracy vital in certain occupations e.g. electrician
Tints may limit ability to drive

20
Q

Why is stereopsis considered when dispensing occupational lenses?

A

Vital for certain tasks e.g. threading a needle

21
Q

Why is possibility of ocular hazard considered when dispensing occupational lenses?

A

Hazards at work place= chemical , mechanical and radiations.

22
Q

Difference between top and bottom add in double D style?

A

Top add is 60% of that at the bottom

23
Q

Describe DBUB- Double round seg

A

Up and down adds are individually specific. Any combination of intermediate, near or distance can be used.

24
Q

Does the main lens in DBUB have to be for distance RX?

A

No, the main lens can be intermediate RX even, depends on PX’s needs.

25
Q

Variable separation between 2 segments in DBUB?

A

Minimum of 4mm

26
Q

Why is DBUB a better choice then DD?

A

Because DBUB has variable separation.

27
Q

For a typical progressive lens, the more add power in a lens results to?

A

More surface astigmatism

28
Q

Fitting of degressive lenses?

A

Fitting in the lower limbus with respect to HCL.

29
Q

When are restricted distance lenses used?

A

When Px requires even more depth of vision. This is a vocational lens.

30
Q

Structure of restricted distance lens?

A

Similar to degressive lenses but ‘distance’ portion of the lens is at the very top. This lenses provide patients with a wider intermediate and near vision than traditional varifocals.

31
Q

Semi distance lenses used for driving?

A

Not suitable

32
Q

Bifocal lenses have how many focal points?

A

2 focal points- For distance and near

33
Q

When does a px considers to wear a trifocal over a progressive lens?

A

Trifocal is considered in Px’s with no accommodation.

34
Q

Problems with bifocals/trifocals over occupational lenses?

A

bifocals/trifocals: segment is not at an ideal position for intermediate tasks. Px’s have to tilt head back and keep adjusting frame to see things, also field of view is not sufficient.

35
Q

2 common choices for double segments?

A

DD28 & DBUB

36
Q

Which segment has a higher value in DD28- Top vs bottom?

A

Top is lower by 60% compared to bottom

37
Q

What does it mean- In DDUB, Up & down adds can be individually specified?

A

The up and bottom segs can be anything- intermediate, near or distance. the main lens doesn’t have to be for distance.

38
Q

Why can’t standard progressive lenses be used as occupational lenses?

A

Standard progressive lenes: the distance RX lies directly infront of Px’s pupil hence, provides distance rx vision- this is not useful for daily tasks and this doesn’t offer comfortable vision for long working hours.

39
Q

Benefit of moving from intermediate to add instead of distance to add?

A

Intermediate –> add: small add power required, provides a longer corridor with less distortion and reduces unwanted surface astigmatism.

40
Q

4 hobbies or occupations where Px will benefit from a degressive lens?

A

Office worker, for people that enjoy social time (playing cards), cooks, decorates, barber and head dressers.

41
Q

How can you identify is Px has accommodation using RX?

A

If working distance coincides with add – px has no accommodation.

42
Q

Problems with ordinary reading glasses, bifocals and trifocals for intermediate work?

A

Ordinary reading lenses: not enough depth of vision.
Bifocals: Will miss intermediate area all together.
Trifocals: May not have enough large areas.

OP2201- Dispensing (7 decks)

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