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Pediatrics > Visual Acuity > Flashcards

Visual Acuity Flashcards

1
Q

When are VAs measured?

A

first at every examination with the exception of chemical burns

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2
Q

How do VAs guide an examination?

A

determine if something is wrong optically or pathologically

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3
Q

Poor attention could result in…

A

decreased measured VA

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4
Q

What are the four testing methods?

A

minimum visible/detection, minimum separable/resolution, vernier, and recognition

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5
Q

What is detection acuity?

A

whether or not an object is present, similar to visual field test, not often used

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6
Q

When might you use detection acuity?

A

if child is thought to be blind or vision development is delayed, can child see 1mm candy at different distances

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7
Q

What is the main problem with detection acuity?

A

it is not standardized

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8
Q

What is resolution acuity?

A

can you see the stimulus as compared to the background

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9
Q

What is the stimuli in a resolution acuity?

A

square wave, sine wave, checkerboard

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10
Q

What is vernier acuity?

A

the smallest area of misalignment that can be detected between 2 stimuli, used experimentally not clinically

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11
Q

What is recognition acuity?

A

the most common, snellen, landolt C etc

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12
Q

What is landolt C?

A

a forced choice recognition acuity test useful for preschool or nonverbal patients, takes a bit of time

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13
Q

What is the takeaway from the visual acuity development studies in 1939, 1962, and 1978?

A

newer studies have more sophisticated tests and record better acuities in the the corresponding ages

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14
Q

What are the infant VAs from VEP?

A

2 months 20/150, 4 months 20/80, 6 months 20/30

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15
Q

What is a limit of VA testing in children?

A

cognitive abilities are not the same and take time to develop, boredom/loss of attention is a problem too

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16
Q

What are structural limits of VA testing in children?

A

cortical immaturities, foveal cone immaturities, and foveal pit

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17
Q

What is cortical immaturity?

A

incomplete myelination of optic pathways

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18
Q

What are foveal cone immaturities?

A

short and stubby cones until 4 yrs, less densely packed/no tight junctions until 3-4 yrs

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19
Q

What is foveal pit immaturity?

A

variability in morphology even age matched, by 17 months the pits are more adult like (1.5 years)

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20
Q

How do you test VAs?

A

age appropriate target, monocularly w/ no peeking if possible, binocularly if unable

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21
Q

What objective tests can be used to assess VAs?

A

retinoscopy, cover test, health

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22
Q

Infant VA testing

A

occlude with sticky patch or mom/dad’s hand, infants like to look at faces, should be concerned with asymmetric responses to oculsion

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23
Q

What is the Heidi smile test?

A

screening for development, eye contact at 8 weeks, social smile at 12 weeks, Heidi smile at 3 months (recognizing faces)

24
Q

What is CSM?

A

central, steady, maintained a monocular penlight test for gross assessment of fixation and acuity

25
Q

What does central mean?

A

light is centered on the pupil

26
Q

What does steady mean?

A

the eye is steady, no nystagmus

27
Q

What does maintained mean?

A

eye is fixating on target or picks up fixation

28
Q

What does OD: CSM OS: CSUM mean?

A

poor acuity OS

29
Q

What does CUSUM OD, OS mean?

A

nystagmus with poor acuity OD/OS

30
Q

What is fixate and follow?

A

grosser measurement of fixation monocularly with penlight, document F&F OD, OS

31
Q

What does vertical prims test?

A

determines if there is a fixation preference, suspect amblyopia if 2+ lines difference, strabismus too

32
Q

What is the vertical prism procedure?

A

have a patient fixate on a near object, place 10 pd BD or BU in front of 1 eye, if child sees double the eyes will move up and down between the images and there is no fixation preference

33
Q

What is forced preferential looking?

A

resolution VA, grey vs spatial frequency gratings, infants will look at something instead of nothing

34
Q

How do spatial frequency gratings work?

A

one black and one white stripe= 1 cycle, thinner stripes= higher spatial frequency and better VA

35
Q

What is the spatial frequency grating notation?

A

cycles per cm that can be converted to cycles/degree looking at a table or performing at 55 cm, cycles/cm=cycles/degree, closer=easier, farther=harder

36
Q

What is TAC?

A

Teller Acuity Cards, forced preferential looking, ranges from 38 cycles/cm to 0.23 cycles/cm which is 20/2400 to 20/10

37
Q

What is 30 or 32 cpd?

A

by convention 20/20 but cpd is not really equal to Snellen

38
Q

What is the TAC set up?

A

test distance can be 38/55/84, correct 70-75%

39
Q

What are preferential looking problems?

A

time consuming, boredom/attention, does not equate to snellen, objectivity of examiner, cost

40
Q

What are preferential looking attention grabbers?

A

fan child, hide face, tap on card, puppet, noise maker

41
Q

What are VA FPL norms?

A

1-2 months VA 1.3 cpd (20/470 @55 cm), 6 months VA 5 cpd (20/100 @55 cm), around 3-5 years have adult levels

42
Q

When do kids reach adult level VAs?

A

3-5 years old

43
Q

What are Lea paddles/gratings?

A

FPL test with different spatial frequency gratings

44
Q

What is the Lea paddle technique?

A

@57 cm hold gray paddle over striped paddle, separate paddles at equal speeds and distances, see if child’s gaze follows stripes

45
Q

What are advantages of lea paddles?

A

cost, portable

46
Q

What are disadvantages of lea paddles?

A

not snellen equivalent, time consuming, observer bias boredom, look at your face instead

47
Q

Why use a distance of 57 cm for lea paddles?

A

at 57.2 cm, cycles/cm=cycles/degree

48
Q

What is OKN?

A

optokinetic nystagmus, involuntary eye movement induced by speed of motion of the visual field, induced to hold images stable on retina with head/world movemnt

49
Q

How does OKN present?

A

smooth pursuit in direction of target and saccade back (jerk nystagmus)

50
Q

What is the OKN procedure?

A

@40 cm, patient fixates stimulus, slow eye movement in direction of rotation and rapid movement backwards

51
Q

What must a patient do to elicit an OKN response?

A

must pay attention to the stripes and accommodate to the stripes

52
Q

Is OKN truly foveal?

A

no, deep central scotoma= reduction of gain by ONLY 10-30%, test not particularly affected by blur and can get a positive response even with high refractive error

53
Q

T/F absence of OKN = blindness

A

false, could be lesions in OKN in cortex, cerebellum, brainstem, cortical dysplasia, cortical blindness

54
Q

Why is it difficult to determine VA from OKN?

A

may be useful in determining abnormal binocularity in infants based on asymmetric responses, generally if response to horizontal and vertical you can anticipate 20/400

55
Q

OKN in infants

A

binocular OKN is robust in infants regardless of direction, monocular 1-2 month old infants only show OKN with temporal to nasal motion due to cortical immaturities, symmetrical at 3 (or 5-6) months

56
Q

Asymmetric OKN responses seen in children and adults with abnormal binocularity result from

A

strabismus, anisometropia, unilateral congenital cataract

57
Q

What should you do when a child shows no visual response?

A

child should blink to startle and light, flick fingers at child’s eye or shine bright light

Pediatrics (22 decks)

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