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Ophthalmic Lab Fundamentals > Vertical Imbalance > Flashcards

Vertical Imbalance Flashcards

1
Q

Vertical Imbalance

A

Difference in Total Power at 90 degrees x reading levelDivided by constant of 10 (Prentice’s Rule)

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2
Q

6 ways to correct VI

A
  1. Two pairs of glasses 2. Prism segments 3. Fresnel press-on prisms 4. Dissimilar segments 5. R-compensated segments 6. Slab-off prisms
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3
Q

Fresnel Principal

A

A series of small plastic prisms lying adjacent to each other on a thin platform of plastic Much thinner than a conventional ophthalmic prism 6 month life span Quarter increments 0.25, 0.50, 0.75 etc

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4
Q

What are the rules for Prism Segments?

A

Prism goes in both eyes Use increments of 0.5D, 1D, 1.5D Never see, rare, in glass only, ugly, expensive, long time to make Doesn’t matter which increment you use for each eye Goal is to cancel prism in chosen eye

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5
Q

When do you use Fresnel prisms?

A

Better for high diopters When you need quarter DioptersNot clearest vision, lose visual acuityAphakias, post cataract patients with no lenses

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6
Q

When do you use Slab - off prism?

A

When the vertical balance is present with antimetropia Meaning two different signs for each eye with a big difference between the powers

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7
Q

Slab off/ Bicentric Grinding

A
  1. Get the Vertical Prism 2. Most Minus BD / Least Plus BU 3. Prescribe Slab off Prism -MM BU in same eye to neutralize -LP BU in same eye to neutralize
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8
Q

How many choices are there for R-Compensated Segments?

A

7 choices One has to be R-4 R-4, R-5, R-6, R-7, R-8, R-9, R-104mm - 10mm

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9
Q

What are R-Compensated segs?

A

Round segs that have the bottom or top cut off in order to change where the OC ends up

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10
Q

When do you use R-Compensated Segs?

A

Only good for small amounts of vertical imbalance Can only separate the OCs by 6mm Glass durabilityBig in the Midwest

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11
Q

Do you know the BTS’s for doing dis-similar segs?

A
  1. TK/Kryptok/Round 22 = 11mm 2. Any fuses FT = 5mm 3. Ribbon Seg/Bar Seg 22 x 19 = 4.5mm // 22 x 14 = 7mm 4. Curve Top/Panoptik = 3.5mm 5. Round 22 = 11mm // Round 25 = 12.5 mm6. FT one piece = 5mm 7. Executive = 0 8. Ultex A and AA = 19mm 9. Blended/Seamless 22=11 mm 28=14 mm 10. Ultex B = 11 mm FT 45/ Welsh FT/ Thin Line 35 = 0
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12
Q

For which VI corrections do you use MMLP?

A

Dis-Similar Segs R-Compensated Segs Slab off Prism

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13
Q

Which lens has the VI?

A

Minus Lens has the imbalance in the strongest lens Plus lens has the imbalance in the most plus, always base up

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14
Q

Explain the need for intermediate vision.

A

Their is an inevitable loss of accommodation that results in the loss of clear vision at arm’s length, 20” to 30”. As presbyopia advances with age after 40, the add power becomes greater than the person’s accommodation. They get an intermediate blur at arm’s length. Bifocal is too strong to see further out than arm’s length and their accommodation is not strong enough to bring that area into focus.

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15
Q

What do we have to correct intermediate vision?

A

Progressives Trifocals Bifocals SV lenses for specific purpose like sheet music

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16
Q

What are examples of occupational progressives?

A

Zeiss Gradal RD, the Varilux Interview, Sola Access, Hoya Tact II, AO Technica, and the Shamir Office

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17
Q

Intermediate Vision definition

A

Distance will vary -16” to 24” SV - piano glasses Bifocal -top intermediate/bottom reading Trifocal -three focal lengths Usually prescribed after 2.00 add, not always Age dependent/use dependent

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18
Q

Donders

A

Ophthalmologist charted how much accommodation people had at various ages 60 yr old, +1 D left

19
Q

11 Common Trifocal Types

A
  1. Executive 2. Flat Top 3. E.D. Trifocal 4. Progressives 5. Smart Seg 6. Occupational/Vocational Lenses 7. Double Flat Top 8. Double Round or Basketball Seg 9. Double Executive or E Line 10. Quadrifical 11. Rede-Rite
20
Q

Executive Trifocal

A

Glass or plastic, one piece, 7mm intermediate segment height

21
Q

Flat Top Trifocal

A

Glass or Plastic, fused or one piece Plastic Only =7x25 7x28 8x35Glass Only 9x35 7x35 1st measurement is distance btw first 2 lines

22
Q

E.D. Trifocal

A

Plastic only, executive with a flat top segment Near Rx in FT segment Intermediate under executive line

23
Q

Progressives

A

All one-piece, segment on the front Many different sizes and configurations Intermediate section small with distortion on each side Keyhole

24
Q

Smart Seg

A

Made by SolaA FT design that incorporates an intermediate portion at the top of the segment30mm x 24 mm 30mm length of FT 24= 12 mm intermediate 12 mm near

25
Q

Occupational/Vocational Lenses

A

Lenses designed for a specific function They often will fill a special need required for a hobby/employment

26
Q

Double FT

A

22mm, 25mm, 28mm diameter only Glass or plasticThe upper segment may be for near vision or intermediate

27
Q

Double Round or Baseball seg

A

Round 22mm or 25mm segments Glass or plastic Top round segment could be intermediate or near

28
Q

Double Executive or E line

A

Glass or plastic Intermediate or Near Then Distance Then Near The Distance portion is 10-14mm long

29
Q

Quadrifical

A

Vision Ease Glass only A double FT and smart seg on the bottom

30
Q

Rede-Rite

A

Essentially, an upside down Ultex Looks like an OliveUpside down Ultex A

31
Q

What type of intermediate lenses would you recommend for piano players who need to read sheet music?

A

Single Vision intermediate

32
Q

Who would wear trifocals?

A

Progressive non-adapt

33
Q

Who would wear occupational lenses?

A

Musicians, IT, laboratory personnel

34
Q

Vertex distance

A

From the front surface of the cornea to the back of the lens

35
Q

Ideal vertex distance

A

13.75mm

36
Q

Reason for Vertex Distance Compensation

A

If a person with a +/-5.00 Diopter or greater lens is refracted at one distance and the glasses are fitted at a different distance, a disparity in visual acuity will exist

37
Q

How do you determine the length that focused light rays hit inside the eye? Using your knowledge of vertex distance compensation, how far do focused light rays hit inside the eye if the optician fits the glasses at 14mm?

A

100mm-distance optician first glasses at = distance focused light rays hit the eye 100mm is the retina

38
Q

Four rules of Vertex Distance Compensation?

A

A minus lens moved inward INCREASES it’s effective power A minus lens moved outward DECREASES its effective power A plus lens moved inward DECREASES its effective powerA plus lens moved outward INCREASES its effective power

39
Q

What’s the relationship between focal length and lens power?

A

Shorter Focal Length = stronger lens power Longer Focal Length = weaker lens power

40
Q

A high hyperope patient was examined at 8mm and fit at 13 mm, did you move inward or outward? Which rule?

A

Moved outwards/away Increases its effective power You need the opposite So you need a weaker lens

41
Q

Vertex Compensation

A

When the frame does not sits at the same vertex distance as the phoropter/trial frame did during the examination Manipulating Focal Length

42
Q

Four Rules Simplified

A

Plus Moved away gets stronger Plus Moved Closer gets weaker Minus moved away gets weaker Minus moved closer gets stronger

43
Q

Shamir office

A

Shamir Computer™ is designed to provide patients with a wide field of near viewing with clear vision up to 5 feet, which is a far greater depth of field than that offered by conventional reading lenses. It is ideal for patients working at a computer or who are primarily stationary at their desk/workstation throughout the day. Professions that may benefit from Shamir Computer™ include architects, post office clerks, software engineers, data entry clerks, graphic designers, pianists and more.

44
Q

Reverse Slab-off increments for Younger

A

1.5, 2, 2.5, 3, 3.5, 4, 5, 6

Ophthalmic Lab Fundamentals (9 decks)

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