Aspheric Lenses Flashcards

1
Q

2 advantages of aspheric lenses:

A

reduce off axis aberrations

reduce lens thickness

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2
Q

asphericity of Q=0 means:

A

it’s a circle

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3
Q

Q>0 is a _ ellipse, and _ curved

A

oblate, more

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4
Q

-1

A

prolate, less

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5
Q

if a plane cuts through a cone that is parallel to the side of the cone, a _ is created

asphericity Q= _

A

parabola

-1 (always flatter than circle and ellipse

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6
Q

incident rays parallel to the axis reflect off a paraboloid, and always pass through the focal point; therefore there are no _ aberrations

A

spherical

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7
Q

if a plane intersects the cone and its base, the curve is a _

Q=_

A

hyperbola

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8
Q

from flattest to steepest:

A

hyperbola, parabola, prolate ellipse, circle, oblate ellipse

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9
Q

as Q becomes more negative, sagittal depth _

A

decreases

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10
Q

power at the tangential meridian of an ellipsoid is the _

power at the sagittal meridian is the _

A

minimum

increasing.. max, idk? (smaller radius of curvature)

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11
Q

vertex power is _, (greater than tangential and sagittal)

A

maximum

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12
Q

power drops off faster along the _ meridian

A

tangential

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13
Q

with full aspheric lenses, the aspericity starts _ at the vertex

A

immediately

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14
Q

nonfull aspheric lenses have _
central area that is spherical is called: _
outer part of the lens is usually aspheric for _

A

a spherical component and an aspherical component
cap
progressive add power

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15
Q

aspheric lenses are flatter than spherical, so their sagittal depths are _

A

smaller

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16
Q

high +: a lens with an aspheric base curve will flatten the front lens which:

  • betters the cosmetics
  • decreases RA and curvature of field
  • reduces _
A

thickness

17
Q

plus lenses: periphery of front and back surfaces are _ ,center remains spherical

A

flattened (entire lens thinner)

18
Q

minus lenses: peripheral portion of front is _

peripheral portion of back is _

A

steepened
flattened
(center is not changed)

19
Q

an aspheric lens will produce _, and is used for _

A

progressive power changes

PALs (distance portion is spherical)

20
Q

aspherical lenses are best used for _ rxs

_ lenses are best used if astigmatism is present

A

spherical

atoric

21
Q

atoric lenses have _ surface powers

A

2 aspheric

22
Q

like aspheric lenses, atoric lenses will

_ peripheral aberrations

A

reduce

23
Q

atoric lenses are recommended for >_D of astigmatism

A

2.00

24
Q

atoric lenses are never used for _ rxs

A

spherical

25
Q

finished single vision atoric lens has
_ front surface
_ back surface

A

spherical

atroic

26
Q

semi finished single vision lens has
_ front surface
_ back surface

A

atoric

spherocylindrical

27
Q

can decentration be used in an aspheric lens?

how is prism achieved?

A

NO (pt must look through optical center)

must be grounded into lens (only way)

28
Q

to identify aspheric lens:

  • move clock along _ meridian, if power changes it is aspheric
  • use _ pattern to see if peripheral aberrations are min
  • look at front and back surfaces compared to spherical lenses of similar rxs (experience)
  • _ marking
A

tangential
grid

manufacturer

29
Q

when dispensing aspheric lenses: DRP must coincide with _

A

OC

30
Q

lenses with aspheric peripheries can be decentered 1mm for every 2 degrees of pantoscopic tilt.. but no more than _ degrees of tilt is allowed

A

10

31
Q

when to dispense aspheric lenses:

  • _plus or minus
  • _ patients
  • people who want _
  • _ wearers to reduce weight
A

high
anisometropic
good cosmetics
old