Optics Lecture 4 Flashcards

1
Q

Can we prescribe refractive correction from wf measurements

A

No

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2
Q

Gold standard method of refraction

A

Clinical phoroptor method

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3
Q

Give the comprehensive description of eyes optical aberrations from which the retinal image can be computed using the theory of physical or geometrical optics

A

Shack-Hartmann aberrometry

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4
Q

What types of aberrations to we fix w/o surgery

A

Astigmatism and defocus

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5
Q

How do we correct HO aberrations

A

Surgery

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6
Q

How are subjective a objective refraction different in terms of chromatic aberrations

A

By wavelength used

  • Obj - IR light
  • sub - white light
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7
Q

How are subjective a objective refraction different in terms of stiles-Crawford effect

A

PR are fine tuned toward center of pupil

- light from periphery isnt caught by cones

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8
Q

How are subjective a objective refraction different in terms of max plus technique

A

Obj - give max +

Sub - give mean

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9
Q

How are subjective a objective refraction different in terms of measurement plane of the instrument

A

Sub - spectacle place

Obj - corneal plane

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10
Q

What must you do to compare obj (wf) with sub (va)

A

Make all factors the same

  • wavelength
  • Pupil size
  • Plane of measure
  • Accommodation
  • Measurement technique
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11
Q

What is the population mean for subjective refraction for 3mm pupil

A

.19D

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12
Q

What is the population mean for subjective refraction for 6mm pupil

A

.23D

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13
Q

Does the refractive error for subjective method change when the pupil dilates

A

No

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14
Q

What is the population mean for objective refraction for 3mm pupil

A

Hyperopic relative to subjective mean

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15
Q

What is the population mean for objective refraction for 6mm pupil

A

Myopic relative to subjective

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16
Q

When HO aberration are small, how do all of the metrics relate

A

They are the same

17
Q

When HO aberrations are large, how do all the metrics relate

A

Different metrics give different refraction

18
Q

Are many objective refracts accurate/precise

A

Yes

19
Q

Is zernike accurate and precise

A

No, too myopic

20
Q

Is paraxial accurate/precise

A

No, too hyperopic