Module 4 Frame Selection Flashcards by Brenda S

What is effective power?

The vergence power a lens has at a position other than that occupied by the lens itself

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For plus lenses, as the lens moves further from the face, does the effective power become stronger or weaker?

stronger

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What is the formula for effective power?

D(E) = D(L) / (1 + dD(L))

d is + if lens is fit closer to the face than refracted and vice versa

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For minus lenses, as the lens moves further from the face, does the effective power become stronger or weaker?

weaker

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What bridge is shaped like a saddle, fits perfectly, and evenly distributes weight?

Saddle

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What bridge has nose pads attached to the back side of frame, is for narrow noses, and distributes weight on the sides of the bridge?

Semi-saddle or modified saddle

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What bridge has an old fashioned design where the top flares out marginally, weight is on sides, and has a very thin bridge?

Keyhole

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What are the two types of bridges for metal frames?

Adjustable nose pads

Uni-fit bridge

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What is a uni-fit bridge?

Similar to saddle bridge

For safety, children and high powered glasses

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What is a metal saddle?

Weight is distributed on top of nose
John Lennon style
NOT for high powered lenses

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What are the parts of the temples?

Butt portion
Dowel hole
Shaft (shank)
Shield
Bend
Earpiece

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What are the parts of the frame?

Endpiece
Bridge
Eyewire or Rim
Shield
Nosepad

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What are the types of temples?

Skull
Convertible
Comfort cable
Riding bow
Library

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What are Skull temples?

Follow contour of ear

Very popular

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What are Library temples?

Held on by pressure (bow temples inward)

Half eyes, military aviators

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What are Convertible temples?

Worn like skull or library temples

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What are Riding Bow temples?

Plastic construction

Children’s and safety frames

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What are Comfort Cables?

Metal construction

Children, safety, or tradesman

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What is the proper frame width?

Equal to the widest part of the face

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For what face type would you increase the depth of frame vertically?

Longer face

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For what face type would you decrease the depth of frame vertically?

Shorter face

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What type of frame aids in shortening a longer face?

Darker solid colored frame

Vertically gradient frame

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What are the pros of Cellulose Acetate frames?

Zyl
Shell
Easily adjustable with heat

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What are the cons of Cellulose Acetate frames?

Sensitive to solvent (acetone)

Dries out

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What are the pros of Cellulose Propionate frames?

``` Lightweight, strong, ultrathin Used for big frames Allergic reactions minimized Scratch resistant Retains colors ```

What are the cons of Cellulose Propionate frames?

Heat sensitive Cold snap Solvent sensitive

What are the pros of Fiber Graphite frames?

30% lighter than zyl Flexible High tensile strength Not sensitive to solvents

What are the pros of Polycarbonate frames?

Lightweight Most impact resistant material Safety frames or lenses

What are the cons of Polycarbonate frames?

Scratches easily Difficult to adjust Sensitive to solvent Cold snap lenses

What are the pros of Optyl frames?

Lightweight Keeps it's color Durable Long lasting

What are the cons of Optyl frames?

Must handle when hot Memory No water

What are the pros of Cellulose Nitrate?

Good polish | zylonite

What are the cons of Cellulose Nitrate?

Flammable | Banned by the FDA

What are the pros of Monel?

Combo nickel (63-70%) and copper Strong and stable Resistant to corrosion

What are the pros of Nickel?

Bends without breaking | Used with stainless steel

What are the cons of Nickel?

Patients are allergic to it

What are the pros of Nickel Silver (German Silver)?

Strong Aides in long lasting adjustments Contains >50% copper, 25% Nickel, and Zinc

What are the cons of Nickel Silver (German Silver)?

Brittle

What are the pros of Phosporous Bronze?

Mostly copper Flexible Good for thin temples

What are the cons of Phosporous Bronze?

Springy | Tarnishes

What are the pros of Stainless Steel?

``` Strong Thin Noncorrosive Good for outdoorsmen Manganese, nickel, iron and chromium ```

What are the cons of Stainless Steel?

Difficult to adjust | Small % of wearers are sensitive to nickel in product

What are the pros of Titanium?

Corrosion-resistant | Lightweight

What are the cons of Titanium?

Requires special tools to work with material

What are the pros of Aluminum?

Very popular | Very few adjustments

What are the pros of Beryllium?

Strong material

What are the cons of Beryllium?

Costly | Rarely used

What are the 7 basic facial shapes?

``` Oval (can wear almost any shape frames) Round Triangle Inverted Triangle Long Square Diamond ```

What is important when suggesting frame types based on facial shape?

Think opposites

What is the boxing system?

System of lens measurements based on the enclosure of a lens by horizontal and vertical tangent to form a box

What is the "A" measurement or eyewire in the boxing system?

The horizontal dimension of the boxing system rectangle that encloses a lens or lens opening

What is the "B" measurement or eyewire in the boxing system?

The vertical dimension of the boxing system rectangle that encloses a lens or lens opening

What is the Geometrical Center Distance in the boxing system?

The distance between the two geometrical centers It can be measured from the far left side of one lens opening to the other Also called PD and the distance between centers or DBC

What is the Effective Diameter in the boxing system?

It is found by doubling the distance from the geometrical center of the lens to the apex of the lens bevel farthest from it

What is DBL in the boxing system?

The distance between the two boxes when both lenses are boxed off in the frame and is measured on the frame as the distance from the inside nasal eyewire grooves across the bridge area at the narrowest point

How much is added to the A measurement and subtracted from the DBL, if measured in plastic frame?

0.5 mm

What are frame requirements for high minus wearers?

``` Small eyewire size, large bridge size Round corners High index lenses Flat or rolled bevels Polished or rolled edges AR Aspheric lenses Biconcave or blended myodisc design for very high minus Thick rims, plastic ```

What are the frame requirements for high plus wearers?

``` Smaller eye size Round shapes ED + max of 2 mm Short vertex distance Adjustable nosepad Aspheric design High index lens materials ```

What is the formula for front surface power?

D = (n(r) - 1) / r

What is the formula for back surface power?

D = (1 - n(r)) / r

What is the lensmakers equation?

D(N) = +_(n-1)/r1 +_(n-1)/r2

What is vergence?

The curvature of a wavefront at a specific distance from the origin

+ Power has what kind of relationship with focal length?

Inverse relationship Longer focal length, lower power Shorter focal length, higher power

What is vertex?

The distance from the front of the eye to the back of the lens Normally 14 mm

How do lenses create power?

Curvature Thickness Refractive index

How do lenses create power?

Curvature Thickness Refractive index