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KMK Optics > Optics II > Flashcards

Optics II Flashcards

1
Q

Punctum Remotum

A

The far point
Conjugate to the axial retinal point.
A point object at the far point will result in the formation of a point image at the retina.

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2
Q

Punctum Proximus

A

Near point is conjugate to the retina when the eye is exerting max accommodation. Similar to the far point, except when the eye is fully accommodating.

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3
Q

The far point is located where for emmetropes, hyperopes, and myopes

A

Emmetropes- infinity
Hyperopes- past infinity or behind the retina (virtual)
Myopes- between the eye and infinity (real)

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4
Q

Power of an emmetrope, myope, and hyperope eye

A

Emmetrope: +60
Myope: Stronger. +65
Hyperope: Weaker. +55

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5
Q

What 2 things can induce night myopia?

A

Increased spherical aberrations

Light levels are too low to fully relax accommodation when viewing distant objects.

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6
Q 
Trends of myopia. 
Age 1 
Age 6 
Age 20 
Age 30
A

Age 1: few
Age 6: 2%
Age 20: 20%
Age 30: 30%

Total- between 5-20% of the pop is myopic.

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7
Q

Manifest hyperopia vs latent

A

Manifest- how much is present at subjective

Latent- difference between subjective and objective

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8
Q

Absolute vs facultative hyperopia

A

Facultative- the amount of hyperopia that can be neutralized by accommodation.
Absolute-Hyperopia is too large to be neutralized by accommodation.

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9
Q

At age 5, your patient is a hyperope. Based on their refraction, you can guess their refractive error in 10 years.

Greater than +1.50
+0.50-+1.25
Less than +0.50

A

Greater than +1.50 –> Hyperope
+0.50-+1.25 —> Emmetrope
Less than +0.50 —> Myope

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10
Q

How does amount of hyperopia change from 20-40 and 45+

A

20-40 stays relatively the same. May uncover more as accommodative ranges decrease.

45+ hyperopes and emmetropes show an increase in plus

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11
Q

Example of resolution acuity

What is the normal cut off range

A

TAC
Asking a patient to distinguish a pattern from a uniform patch of equal luminance.

Normal adult has a cut off at 40-60 cpd

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12
Q

Example of recognition acuity

A

Snellen

Only gives info about ability to resolve high frequencies.

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13
Q

The average person has a much better __ than resolution and recognition acuity. About 1 arcsec

A

Minimum detectable acuity

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14
Q

Hyperacuity

A

Person’s ability to sense directional relationships. Ex: Whether 2 lines are parallel.

Result of higher level processing.

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15
Q

MAR

A

Minimum angle of resolution. Measured in arc mins (1/60 of a degree)

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16
Q

A Snellen 20/20 letter subtends an angle of ___ when viewed at 20 feet

A

5 arc mins

Each distinct bar (think of the letter E) makes up 1 arc min.

17
Q

Tumbling E is appropriate for children ages

A

3-6

18
Q

3 examples of matching recognition acuity tests

A

Lea, HOTV, STYCAR

19
Q

Static ret

A

Patient fixates through phoropter at a distant target

20
Q

Nott’s Method of dynamic ret

A

Keep a target in place at 40cm.

Move the ret backward, away from the patient, instead of using lenses. The distance at which neutrality is achieved can be used to determine the lag.

Ex: near card at 40cm, neutrality at 60cm. Lag is 2.50-1.67= 0.83D.

21
Q

Mohindra technique

A

In the dark
50cm
Monocular
Can give a closer estimation to cyclo

22
Q

How to use an astigmatic dial

A

Put up the dial
Fog the patient
Ask which line is darkest
Take the smaller value x 30 to find axis
Add minus cyl until all lines look equal
Then add minus sphere until BCVA

23
Q

Can you do the red/green test on someone who is color blind

A

Yes
The test is based on chromatic aberrations, not our perception of color

It cannot be used unless acuity is 20/30 or better

24
Q

When to use a cyclo refraction

A
  1. Child with convergent strab (must determine if accommodation is contributing)
  2. Child with significant eso at near
  3. Suspecting latent hyperopia
25
Q

A person only uses __% of their accommodative ability comfortably

A

50%

26
Q

Correcting aphakia with plus lenses can lead to what

A

If monocular aphakia–> Aniso and diplopia
If binocular aphakia –>
1. Pincushion (due to high plus lenses)
2. Reduced visual field due to mag. May also cause a ring scotoma.
3. Induced BO at near may cause increased convergence demands

Pt is more at risk for developing AMD due to increased sun exposure. Educate about importance of sunglasses

27
Q

The major meridian of the eye

A

Has the most plus power

Will correspond to the steeper meridian

28
Q

WTR and ATR astig

A

WTR: Horizontal meridian OF THE EYE has less plus. Steep vertical meridian. x180 rx correction

ATR: Vertical meridian OF THE EYE has less plus. Steep horizontal meridian. x090 rx correction

KMK Optics (4 decks)

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