Block 1 Flashcards by Emily Raynor

Instrument to measure sphere, cyl power and axis, add power, and prism power and direction

Lensometry

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Does lensometry measure the front or back vertex power of lens

Back

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What type of telescope is a lensometer

Keplarian

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How to find the -0.25D cyl axis

Bracket

- move in 1 direction until it breaks, then same in the other and put the number in the middle

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Do spec Rx expire

No, unless a date is specified

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Do CL Rx expire

Yes, = 1 yr

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Do you have to set the axis dial to 180 before reading glasses

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When to use the green background while reading

Clear or lightly tinted specs

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When to use the orange background while reading

Dark tint or sunglasses

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What should you always do before putting the glasses in the read

Set power to 0
Set prism to 0
Focus the eye piece

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Different kinds of multifocal lenses

Progressive
Bifocal
Trifocals

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What are multifocal lenses

Have 2 or more lens powers

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Who wears multifocal lenses

Usually over 40

Also, young children with focusing problems

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If kids have focusing problems, which type of multifocal lenses are typically used

Usually bifocals, because progressives are harder to adjust to

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Good for people with issues such as lazy eye; have no areas of distortion

Lined multifocal so

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How to read the add power in a strong Rx (> +/- 5D)

Flip frames to where the temples are facing you

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Progression of lens power from full distance correction at the top to full reading at the bottom

PAL (progressive)

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Plus in the middle of progressive

Fitting point

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Where should the fitting point sit

Center of pupil

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Dot below plus sign on progressive

Prism reference point

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Optical center of PAL

Prism reference point

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Which side of progressive has the add power

Temporal side

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Triangular shape that change the direction of light

Prism

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Which way does light bend in the prism

Toward base

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Which way is the image formed through the prism

Apex

How to determine how much prism is in lens

Where the single line and middle of triple lines intersect

Unit that describes the power of a prism to produce a one cm deviation at a distance of 1m from the lens

Prism diopter

2 ways prism can be incorporated

- ground in | - induced

Grinding he surface of a lens during manufacturing

Ground in prism

Decentering the optical center to utilize the prismatic properties of sphere-cyl lens - prentice rule

Induced prism

What is prentice rule

Prism D = P x d(cm)

If you move the lens around, the intersection will stay off center

Ground in prism

the only way that the mires can be centered is if the lens is decentered

Induced prism

What vertical prisms cancel out

BU and BU in both Or BD and BD in both

What horizontal prisms cancel out

BI and BO

When do you use the prism compensating device

If more than 5 prism D | - cant see both sets of mires

What do the 3 numbers on a temple or bridge stand for

Eye size - bridge width - temple length

Normal range for eye size

40-62 mm

Normal range for bridge

14-24 mm

Normal range for temple length

120-150 mm

Why are the eye-bridge-temple listed on the frame

They are set numbers, cant be changed | - important for frame fit and sizing

Frame measurements: A

Horizontal width

Frame measurements: B

Vertical height

Frame measurements: DBC

Distance between centers

Frame measurements: DBL

Distance between lenses

Frame measurements: ED

Effective diameter | - 2 times the longest radius

Frame measurements: OTL

Length of temple

How different is the near PD from far PD

Usually about 2 mm smaller in each eye

How is pupillary distance measured

Pupilometer

Which direction of decentration if pt PD>frame PD

Move out

Which direction of decentration if frame PD > pt PD

Move in

Distance between bottom edge of lens and top of segment

Seg height

Distance between datum line (center of lens) and top of bifocal/trifocal

Seg drop

Distance the center of the near segment is moved laterally for the OC

Seg inset

Typical segment height of bifocal

Top of lower lid

Typical segment height of trifocal

Lower lid margin

Typical segment height of progressive

Pupil center

Determines the smallest possible lens blank for a given frame and PD combo

MBS = (DBC - PD) + ED

Final step in the manufacturing of eyewear

Inspection process

System of standards and tolerances used to verify eyewear

Inspection process

Formula for finding the power in a certain meridian question

Sphere + Cyl(sin^2theta) - theta being the difference between the axis of Rx and of the meridian in ?

Surfacing of a portion of a lens so as to add a second optical center

Slab off

Formula for vertical imbalance

((Lens P @90) x (distance from OC)) / 10

Distance from back surface of specs to apex of cornea

Vertex distance

As you move closer to the eye, how does the CORRECTION change

Rx get more PLUS the closer you get

Formula for vertex distance

New P = (old P)/(1 - (d in m x old P) D: positive for moving closer to eye, negative for moving away from the eye

How to calculate the vertex distance/new power with a sphere-cyl lens

Do the formula for both the sphere and the cyl powers

Tool used to measure the D power of lens

Lens clock

What refractive index is the lens clock designed for

1.53

When there is a difference in the front and back, how do you find the nominal power

Add the 2 values together

Which part of the lenses to the thickness calipers measure

The thinnest part

Minus lens --> where is thickness measured

Center

Plus lenses --> where to check thickness

The edge

Types of adjustment tools

Pliers, screwdriver set, drill mount kit

Tool used to adjust a plastic frame

Hot air frame warmer

Off-face check

``` X-ing Temple spread Temple fold angle Nose pads Faceform/wrap ```

6 steps to proper adjustment

``` Wearing position Nose pads Horizontal alignment Pantosopic tilt Vertex distance/wrap Temple bend ```

Best frame for high Rx

Full frame

Good for pt that doesn't take glasses on and off often

Rimless

Hybrid of semi-rimless and full

Inline

2 most common metal frame types

Monel | Titanium

2 components of monel

Nickel and copper

Most common plastic frame material

ZYL - zylonite

Common allergies to frame materials

Nickel and silicone