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FS Lectures > Ophthalmology: Introduction to Vision > Flashcards

Ophthalmology: Introduction to Vision Flashcards

1
Q

Define visual acuity

A

Resolving power of the eye

…minimum visible, separable, legible

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2
Q

The denominator in Snellen acuity indicates the distance (in feet) at which a letter will subtend…

A

…a visual angle of 5 minutes of arc

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3
Q

Functional vs Physiological VA limits

A

Functional = 20/10

Anatomical limits = 20/08 (single cone cell)

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4
Q

Which chart is used for VA qualifications for aviation applicants and designated aviation personnel?

A

“Good-Lite” (Sloan Magnetic Randomized Letter) Chart

Note: “Snellen” Eye Chart is the one typically seen in offices on the wall

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5
Q

Emmetropia

A

Standard refractive power and axial length…

  • aka refractive condition where parallel light rays focus on the retina when the eye is at rest…*
  • aka where the image of an object at 20ft focuses directly on the fovea*

“Normal”

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6
Q

Ametropic Eye

A

Non-standard refractive power or axial length

  • Excessive/insufficient power*
  • Longer/shorter axial length*
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7
Q

Myopia

A

“Nearsightedness”

A refractive condition in which light rays focus in front of the retina

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8
Q

Hyperopia

A

A refractive condition in which light rays focus behind the retina

“Farsightedness”

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9
Q

What causes myopia?

A

Excessive power (steeper cornea)

OR

Axial length is too long (“big eye”)

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10
Q

What causes hyperopia?

A

Deficient power (flatter cornea)

OR

Axial length is too short (“small eye”)

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11
Q

Which lenses correct myopia?

A

Minus lenses (diverging/concave)

Note: minus refers to negative focal point (aka left of lens)

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12
Q

Which lenses correct hyperopia?

A

Plus lenses (converging/convex)

Note: plus refers to positive focal length (right of lens)

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13
Q

Excessive refractive ametropia

A

aka excessive power = myopia

“nearsightedness”

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14
Q

Deficient refractive ametropia

A

aka Deficient Power = hyperopia

“farsightedness”

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15
Q

Axial Ametropia

A

Too long = myopia (nearsighted)

Too short = hyperopia (farsighted)

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16
Q

Define accommodation

A

The process of the lens changing its focusing power for near and far distances

Remember…ciliary body relaxed = zonules under tension

CB constricts = zonules relaxed = lens bulges = increased refractive power

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17
Q

True/False

Amplitude of accommodation is independent of age

A

False

  • Presbyopia = normal changes that lead to symptoms at age 40*
  • Pharmaceutical agents (atropine/cyclopentolate/tropicamide) and neurological (rare) causes can also lead to decreased accommodation*
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18
Q

Presbyopia

A

literally “old eyeballs”

Decreased accommodation with normal aging (symptomatic at about age 40)

18D at birth, less than 1D at age 65

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19
Q

Near objects focus ______ the retina in an unaccommodated eye

A

behind

Why presbyopia is corrected with plus lenses

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20
Q

Astigmatism

A

Light focusing in 2 spots due to 2 curvatures on the cornea and/or lens

“Multiple focal points”

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21
Q

Symptoms of Astigmatism

A
  • Reduced vision at distance/near
  • Elongated appearance of lights at night
  • Normal vision during the day, blurry at night
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22
Q

Correction for astigmatism

A

Cylindrical lenses (usually sphero-cylindrical)

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23
Q

True/False

Corneal Astigmatism shouldn’t dramatically change with age

A

True

Unlike lens astigmatism, which increases mildly with age

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24
Q

Lens power (in diopters) =

A

1 / f

  • f = focal length*
  • Note: lenses bend light, the numbers that describe a lens tell us how much they bend light and in what direction*
25
In diopters, how much lens power is there when the focal lenth is 20cm?
+5.00 D *1/0.2m = 5*
26
Converging lenses can be used to correct...
... farsightedness (hyperopia) designated by (+) for positive focal length
27
Concave lenses can be used to correct for...
... nearsightedness (myopia) Concave = diverging, designated at (-) lenses for negative focal length
28
Spherical lenses bend light...
the same amount in all meridians (or axis) *Can be plus or minus*
29
Cylindrical lenses bend light...
in one meridian (or axis) only
30
True/False Most lenses have a combination of sphere and cylinder power
True *aka spherocylindrical lenses*
31
Anisometropia
Difference in refractive power between the eyes *Ex. OD -1.00 sph and OS +4.00 sph = 5.00 D aniso*
32
O.D.
right eye
33
O.S.
left eye
34
O.U.
both eyes
35
+
convex
36
-
concave (diverging)
37
Visual Acuity from better to worse: HM, NLP, PH, CF, LP
PH \> CF \> HM \> LP \> NLP \*Pinhole Acuity, Counts Fingers, Hand Motion, Light Perception, No LP
38
DVA required for SNA applicants
Uncorrected 20/40-0 or better if corrected to 20/20-0 * Remember...on a "GoodLite" chart* * Note: NVA has the same standards as DVA*
39
True/False There are no uncorrected DVA/NVA limits for SNFOs
True
40
Refractive standards for SNA applicants
Spherical power limits: -1.50 to +3.00 No worse than -1.00 cylinder (astigmatism) No worse than 3.50D anisometropia
41
SNFO must correct to 20/\_\_\_
20/20 -3 (7/10 letters in each eye\*) *\*GoodLite or AFVT*
42
SNFO Refractive Standards
Refraction no greater than + or - 8.00 D in any meridian No more than 3.00 cylinder (astigmatism) No worse than 3.50 anisometropia
43
Aircrew applicant standards: Uncorrected DVA (fixed vs rotary)
Fixed = no limit Rotary = 20/100 uncorrected Note: BOTH must correct to 20/20-3 on GoodLite or AFVT
44
True/False Aircrew applicants have no limit for refractive error
True
45
Designated Class 1 Service Group 1
No platform limitations * Uncorrected DVA **20/100** (must correct to 20/20-0)* * No limit for refractive error* * Anisometropia must not exceed 3.50D*
46
Designated Class 1 Service Group 2
Only restricted from fixed wing carrier ops Uncorrected DVA **20/200** (must correct to 20/20-0) No limit for refractive error Anisometropia must not exceed 3.50D
47
Designated Class 1 Service Group 3
Restricted from fixed wing carrier ops and flying without another SG1/SG2 pilot Uncorrected DVA **20/400** (must correct to 20/20-0) No limit for refractive error Anisometropia must not exceed 3.50D
48
Do designated Class III personnel enter aircraft
No
49
Must carry extra pair of glasses if less than _____ uncorrected
20/100 uncorrected DVA (or less than 20/40 NVA)
50
Stereopsis
Using both eyes for depth perception *Note: any history of strabismus surgery is considered disqualifying for pilots and rotary wing aircrew*
51
Phoria
When your eye has a "party position" (where it goes at rest) Exophoria vs Esophoria
52
Phoria standards for aviators
6 exo/eso 1.5 hyper
53
NOTOSP
No Obvious heteroTropia or Symptomatic heteroPhoria aka NOHOSH
54
How much sensory input is visual?
80%
55
A 20/20 letter "E" at 20 feet is ______ mm high and subtends _____ minutes of arc
8.7mm high 5 minutes of arc
56
A 20/200 letter "E" at 20 feet is _____ mm high and subtends _____ minutes of arc
87mm 50 min
57
Bifocal addition is...
...the **spherical power** added to each eye
58
Pupillary distance is measured in \_\_\_\_\_\_
millimeters
59
Estimating Refractive Error: 20/10 = 20/20 = 20/40 = 20/200 =
20/10 = plano (zero) 20/20 = plano to -0.25 20/40 = -0.75 20/200 = -2.00 to -2.50

FS Lectures (9 decks)

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