Opt. tech. Lenses Midterm knowledge Week 1-2

Base curve of a lens is the ___ curve

Front

Ocular curve of a lens is the ___ curve

Back

Lens with one plus and minus curve is a ____ lens

Meniscus

Lens with plus BC and plus OC is a ___ lens

Biconvex

Lens with minus BC and minus OC is a ___ lens

Biconcave

Lens with plano curve on BC and plus curve on OC

Plano-Convex

A lens with a plano curve on BC and minus curve on OC

Plano-Concave

A convex lens is considered as ___ lenses

Plus

Concave lens is considered as ___ lenses

Minus

Optical unit of power is called:

Diopter

All can be used to measure the D of a lens except:

Keratometer

All are factors that contribute to the power of a lens except:

frame material

How are the curves of a lens measured?

Lens clock

All are the effects of Prism except?

Disperse prism to base

What is a point on the lens where there is not prismatic effect?

Optical Center

What kind of lens magnifies, converges light, is created with 2 prisms base to base, is thin at the edge and thick at the center, gains power when moved away from the eye, loses power when moved toward the eye, and has against motion?

Minus lens

What kind of lens minifies, diverges light, is created with 2 prisms apex to apex, is thin at the center and thick at the edges, gains power when moved toward the eye, loses power when moved away from the eye, and has with motion?

Plus lens

What lens has 2 powers 90 degrees away from each other?

Toric Lens

What lens has no power at the axis and all the power 90 degrees away?

Cylinder lens

Lens with one power

Sphere lens

If you add a -5.00 D lens to a +2.50 D lens, then the combination will be a D lens.

-2.50

If you add a +6.00 D lens to a -1.00 D lens, then the total power will be a D lens.

+5.00

If you add a -6.00 D lens to a +6.00 D lens, then the total power will be a_D lens.

Plano

The BC of a lens is +8.00 and the OC is -6.00. How much is the power of this lens?

+2.00D

The BC of a lens is +8.00 and the OC is -12.00. How much is the power of this lens?

-4.00D

The power of a lens is +4.00, the BC is +10.00. How much is the OC?

-6.00D

The power of a lens is -2.00, the BC is +6.00. How much is the OC?

-8.00D

The power of a lens is +2.00, the OC is -4.00. How much is the BC?

+6.00D

BC of a lens is +6.00 and the OC is +4.00: What type lens is this?

Biconvex

What is Vogel s Rule/ Formula used to calculate?

To find the ideal curve of a lens

What would be the ideal base curve for the following RX: -3.00-2.00X45

+4.00

What would be the ideal base curve for the following RX: +5.00-3.00X95

+9.50

What is the power of this minus form lens with the following curves: BC= +6.00, TC= -2.50, CC=4.00

+3.50-1.50

What is the power of this minus form lens with the following curves: BC= +2.00, TC=-4.50, CC=-5.00

-2.50-0.50

To decrease oblique astigmatism, the best curve is _ D curve because it is a curve which will have the same distance from the center of the eye rotation which is located 13mm behind the cornea.

6.00

Write minus form Rx for the following true powers:+3.00 @ 120+4.00 @ 30

+4.00-1.00×30

Write plus form Rx for the following true powers: plano @60-3.00 @ 150

-3.00+3.00×1.50

Write plus form Rx for the following true powers: +2.00 @ 170-1.00 @ 80

-1.0+3.00×80

Write plus form Rx for the following lensometer readings: (+4.00) (+3.00)x180

+3.00+1.00×90

Write plus form Rx for the following lensometer readings: (-1.00) (plano)x75

-1.00+1.00×75

Write minus form Rx for the following lensometer readings: (+2.25) (+1.75)x95

+2.25-0.50×05

Write minus form Rx for the following lensometer readings: (-3.50) (-4.00)x55

-3.50-0.50×55

Write the Rx for the following lensometer readings in plus form: Sphere lines read -2.00 Cylinder lines read -3.00 Axis is 140

-3.00+1.00×50

Write the Rx for the following lensometer readings in plus form: Fine lines read Plano Coarse lines read -1.25 Axis is 05.

-1.25+1.25×95

Write the Rx for the following lensometer reading in minus form: Sphere lines read +2,50 Cylinder lines read plano Axis is 155

+2.50-2.50×155

Write the Rx for the following lensometer reading in minus form: Sphere lines read -5.00 Cylinder lines read -5.00 Axis is 20

-5.00 sph

Transpose the following Rx: -3.00 - 1.25 x 95

-4.25+1.25×005

Transpose the following Rx: +5.00 -2.50 x 175

+2.50+2.50×85

Transpose the following Rx: -5.00 -3.25 x 45

-8.25+3.25×135

Transpose the following Rx; +2.50 -2.50 x 25

Plano+2.50×115

The_ is the most refractive organ of the eye.

Cornea

The __ is the focusing organ of the eye.

lens

The declining of accommodation with age is called__

presbyopia

The biconvex lens structure inside the eye is called —

crystalline lens

Measuring the SegHt for the bifocal is on _

lower eyelid

Measuring the SegHt for the trifocal is on___

bottom of the pupil

Measuring the Height for a progressive lenses is on___

center of the pupil

For good cosmetics, pantoscopic tilt should be approximately _ degrees.

8-10

What is the tilt called where the bottom portion of the frame Is closer the face?

Pantoscopic tilt

What should you do if a wearer complains that the SegHt is high?

Increase the pantoscopic tilt

What is the tilt called where the bottom portion of the frame is farther away from the face?

Retroscopic tilt

What is the tilt where the lenses have no tilt?

Orthoscopic tilt

The optic centers in Flat top bifocal (FT) is ___ below the segment line?

5mm

Where are the optic center on a Round segment bifocal (Rd)?

on the center of the segmenr

Where are the optic center on an executive bifocals?

on the segment line

In complete sentences, what is image jump?

When crossing the border of the seg, the prism induced by the distance portion is suddenly changed by the amount of prism that is being induced by the segment portion. This sudden change in prismatic effect causes objects to be displaced.

A___ bifocal has the most image jump

round

A bifocal has the least image jump.

Executive

The intermediate segment has_of the ADD power.

50%

A plumber, librarian, pharmacist, and mechanic is best fitted with a _ bifocal design.

Double Segment lenses

A lens with four powers with a trifocal and an upside down bifocal is called _

Quadrafocal

If the power in the distance reads +2.50-0.50 x 180 and the power in the reading segment reads +5.00-0.50 × 180, how much is the total ADD power?

2.50

If the power in the distance reads -5,00-0.25 x 45 and the power in the reading segment reads -3.75-0.25 x 45, how much is the total ADD power?

1.25

A patient wears an fFt 28 with SegHt of 15mm. The seg line is 4 mm below the eyelid margin. He chooses a new fram. The SegHt measured with the new frame from the lid margin is 22mm. What SegHt should the optician order?

18mm

For intermediate glasses, the depth of a trifocal is larger than mm and it is then not for all time wear.

8mm

Trifocals are written in 2 numbers, the first number is the _of the intermediate segment.

depth

Trifocals are written in 2 numbers, the second number is the of the segment.

width

The best way to use a bifocal when viewing the floor is to the chin and look through the distance portion of a lens.

lower

The best way to use a bifocal when reading is to bring chin__ and eye down to look through the bottom reading area of the lens.

up

Rd segments should be fitted

mm higher than FT bifocals.

2

How do you fit a bifocal for a person who keeps his head back?

lower

The usual intermediate depth in an executive trifocal is _mm.

7

Calculate the reading Rx for the following Rx:

OD: -4.25 -2.00x80

OS: -5.00 -1.00x145      ADD 2.50

OD-1.75-2.00×80

Calculate the reading Rx for the following Rx:

OU: +1.00 -0.25x70      ADD 1.75

OU: +2.75-0.25×70

Calculate the reading Rx for the following Rx:

OD: -3.00 -1.00x90

OS: -2.00 -1.50x180      ADD 3.00

OD Pl -1.00×90 OS +1.00-1.50×180

Calculate the standard intermediate Rx for the following Rx:

OU: +4.25 -1.00x170      ADD 2.50

OU +5.50-1.00×170

Calculate the standard intermediate R for the following Rx:

OD: -1.00 -1.00x90

OS: -2.00 -1.00x80      ADD 2.00

OD Plano-1.00×90 OS -1.00-1.00×80

The ___ PD is needed when ordering a pair of bifocal lenses

near

Rd segments should be fitted___ than FT bifocals

higher