ABO Quick Facts Flashcards by Andy Boie

What is a Lens Clock, also known as a Geneva Lens Measure?

Manual device used to measure a lens Base Curve

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Optical tools (Like a lens Clock) and gauges are Calibrated to what index?

1.53

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What two other names are there for a Lensometer?

A Focimeter or Vertometer

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What is a Lensometer?

A device that measures the focal length of a lens and translates that into power reading(the lenses prescription)

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What is a Fused Bifocal?

A Bifocal lens that combines two separate indices

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What is a One Piece Bifocal?

A bifocal where one index achieves add power with differing base curvatures

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What is a lens Mechanical Center?

The point around which a lens is cut and edged (the center of the block)

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What is the Geometric Center?

The single point in a lens at the intersection of the diagonals in the boxed shape

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What is a lens’ Optical Center?

The single point on a spectacle lens through which a ray of light may pass without being deviated

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If you’re given the Decentration and diameter of a round shape, what is the formula to measure the smallest cut out blank diameter?

2 x decentration plus lens diameter

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Describe Flint Glass

It is Leaded, heavy, yellowish in color, and brittle

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What is a Polariscope, also known as a Colmascope, used for?

Tool used to check for strain in an edged lens or to verify stress pattern in air tempered lenses

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What is the formula for Circle of Least Confusion or Spherical Equivalent?

One half of the Cylinder Power plus the Sphere Power

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Chemical Tempering uses “Ion Exchange” to do what?

To strengthen lenses by creating a hard outer surface

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Which element in Photochromic glass creates the lenses changeability?

“Silver Halide”

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What is a Crimping Plier used for?

Used to “crib” or remove excess glass from a lens blank

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What is a Chappel Plier?

A cutting Plier

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How much of incoming light does the front surface of a Crown Glass lens reflect?

4.28% of the incoming light

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What are Lens Calipers used for?

To measure lens thickness

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What does DBL refer to?

To the closest distance between two lenses

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The velocity of light is least in which density of material? Highest or Lowest?

In Highest Density Material

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What does Specific Gravity refer to?

A weight measurement that refers to the relationship between the density of a specific amount of lens material when compared to the density of a specific amount of Water.

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What is Chromatic Aberration?

The breaking up of white light into its component parts.

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What is an Axial Ray?

A name for the ray that passes through a lens without being refracted.

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Will a glass rod immersed in a medium of the same index of refraction be Visible or Invisible?

Invisible

To get a ballpark "Best Base Curve", what should you do?

Add +4.00 to plus powers and +8.00 to minus powers

What is a Retinoscope?

A tool used to measure refractive power in the eye

What is a Tonometer?

measures intraocular pressure in the eye

What is an Ophthalmoscope?

A tool used to view inside the eye

What do Cycloplegics do?

Inhibit accommodation

What is a Scotoma?

a blind spot, an area of retinal vision loss

Where does the fusion of two ocular images take place?

in the brain

What are Rods?

a layer of cells on the retina for peripheral vision, black and white vision, and night time viewing.

What are Cones?

a layer of cells on the retina for color vision and for most acute vision.

What is a Snellen chart used for?

to test distance vision acuity

What is a Jaeger Chart used for?

to test near vision acuity ( J4 or J2)

What do Mydriatic eye drops do?

Dialates the pupil

The 20/200 line on the Snellen Chart is how tall?

8.87 cm tall

What is Kerataconus?

A cone shaped deformity of the cornea

What is the Limbus?

The junction between the cornea and the sclera

What is the Canthus?

The corner of the eye where the lids meet

Define Nystagmus

An involuntary, rapid and repetitive movement of the eyes often associated with light sensitivity, or photophobia

Define Photophobia

Eye discomfort in bright light

Define Glaucoma

An eye disease characterized by a buildup of inter ocular pressure.

Define Aphakic Patients

Patients who have had their crystalline lens removed.

Define Psuedo Aphakic patients

Patients who have had an implant to replace the crystalline lens

What is the average size of a normal pupil in normal lighting?

3 to 5 mm

Define Ptosis

a drooping lid

How is a Ptosis corrected?

using a Ptosis Crutch

How many extrinsic muscles account for the movement of the eye?

Aphakes can benefit greatly by using which type of lens?

a progressive variable focus lens

Define Chiasm

the point where the optic nerves from each eye are combined.

Define Antimetropia

condition characterized by Rx's with opposite signs (- in one, + in the other)

Define Anisometropia

Vertical prismatic imbalance characterized by unequal power and prismatic effect at the reading level

Define Anisiekonia

dissimilar image size from eye to eye due to uneven magnification

The eye is most sensitive in which area of the color spectrum?

yellow/green

To whom are trifocals prescribed for?

for Advanced Presbyopes

Define Tropia

A definite deviation of the eye

Define Phoria

A tendency for the eye to deviate

Eso =

Exo =

Out

Hyper =

Hypo =

Down

Do Photochromic lenses have more or less reaction in warm weather?

Less Reaction

Do Photochromic lenses have more or less reaction in cold weather?

More Reaction

What are Half Round Pliers?

A tool used for American style nosepad Arm adjustment

What are Box Pliers?

a tool used for European style nosepad arms

What is another name for Bicentric Grinding, and what is it used for?

Slab-off. used to correct vertical imbalance

How many optical centers does a Standard Bifocal have after it is fabricated, and how many can be found in a Lensometer?

3 total optical centers, only 2 can be found in a lensometer

What are Absorptive lenses and how are they formed?

Colored glass lenses formed by adding metal oxides to the glass

Which color is the best absorber of Infrared light in a glass lens?

Green glass lens

What are the two types of Dropball Tests on Lenses?

5/8ths inch steel ball for Dress Safety, and 1 inch steel ball for Industrial Safety.

What should the total weight of the Dropball Testing apparatus be?

No less than 27 pounds

Who invented the first Bifocal Lens?

Benjamin Franklin

The back surface of a progressive is spherical or aspheric?

Spherical

The front surface of a progressive is spherical or aspheric?

Aspheric

Which type of prism is easiest to tolerate at the near point?

Base In Prism

What does a wearer experience when a lens has excessive Base Down Prism?

Makes floor or horizontal expanses seem concave and feel like they're standing in a bowl. Vertical objects may seem taller and they may feel like they're walking uphill

What does a wearer experience when a lens has excessive Base Up Prism?

causes the floor or other horizontal expanses to seem convex as they feel like they are standing on a hill. Vertical objects may seem shorter and the wearer feels like he is walking downhill

What does a wearer experience when a lens has excessive Base In or Base Out Prism?

Cause the wearer to see horizontal objects as high at one end and low on the other. The too high side will always be towards the apex

What can be used to neutralize vertical imbalance at near?

use dissimilar segments like Exec/Ultex

What is the Listings Plane?

the imaginary optical plane lying in the X and Y axis

Define Amblyopia

also known as Lazy eye. it's the loss of vision without any apparent defect to the eye. Generally develops in just one eye(though there are exceptions) and is caused by abnormal visual development early in life.

What does Ferrous Oxide do to lenses?

Gives lenses a green color and UV as well as Infrared absorption

Dispersion is categorized by what?

By Abbe Number, or as it is commonly known by Constringency Value or Nu Value.

How much does the 5/8th inch standard Dropball weigh?

0.56 Ounces

Bifocal add power is equal to what?

to the difference between the back vertex measurement of the distance and near lensometer readings.

Which lens design delivers the least off-axis viewing blur?

a corrected curve "Best form" lens design

Are Impact Resistant lenses unbreakable?

What are the parameters of the visible spectrum?

Approximately from 400 to 750 nm

The eye as an optical system generates approximately how much refractive power?

60 diopters

How much of the refractive power in an eye is from the cornea?

40 diopters

Plus powered lenses moved farther away from your eyes make the lens strength stronger or weaker?

Stronger

Plus powered lenses moved closer to your face make the lense strength stronger or weaker?

Weaker

Minus powered lenses moved farther away from your face make the lense strength stronger or weaker?

Weaker

Minus powered lenses moved closer to your face make the lense strength stronger or weaker?

Stronger

Name the 4 standard Temple Lengths

5 1/4 in = 135 mm 5 1/2 in = 140 mm 5 3/4 in = 145 mm 6 in = 150 mm

When fitting a child with a segmented bifocal, it is common to do what?

Split the Pupil

When given multiple lens materials, how would you determine which is the thinnest?

choosing the lens with the highest index

What is the best lens for water activities?

a polarized lens

Does Medicare cover cataract surgery?

Yes

Optyl frames require a lens to be edged how many mm over the marked eyesize?

1/2 mm

Does Optyl material stretch or shrink?

It will stretch somewhat, but it will NOT shrink

The safest lens in all circumstances is what?

Polycarbonate

Any questions involving prismatic effect due to wide or narrow pd's first require location of the power at what angle?

180 degrees

Any questions involving prismatic imbalance at the reading level first require location of the power at what angle?

90 degrees

Snell's Law deal's with what 2 things?

Reflection and refraction

An Un-AR coated glass or plastic lens will reflect what percentage of light? What percentage of light will it transmit?

reflect 8% and transmit 92%

What is the focal length of a 1 Diopter lens?

1 Meter

How much will a 1 diopter prism deviate a ray of light at a distance of 1 meter?

1 cm

What is the Radius of Curvature of a 1 diopter lens?

530 mm

Formula to measure Focal length in meters

1 divided by dioptric power

What is 1 Meter in cm, mm, and Inches?

100 cm, 1000 mm, 39.37 in

Prentice Rule

Prismatic effect = (distance move x dioptric power) divided by 10

Name the 5 types of Astigmatism

Simple Myopic, Simple Hyperopic, Compound Myopic, Compound Hyperopic, and Mixed

How many years must a patient records for impact resistance be kept?

3 years

How do you check the amount of prism that is ground into a SLAB OFF lens?

using a Lens clock, place lens clock parallel above the Slab line and measure the BC, then turn the lens clock perpendicular with the center pin centered on the Slab line and measure that BC. then subtract the two numbers to get the difference

What is a Meniscus Lens?

a crescent shaped lens, one side concave and one side convex, with one side having a 6 base curve