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clinical low vision > midterm > Flashcards

midterm Flashcards

1
Q

The bigger the size of the object, the bigger is the image that is formed in the retina.

A

Relative Size Magnification

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2
Q

The closer the object is to the eye, the bigger it will seem.

Depends on the distance

A

Relative Distance Magnification

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3
Q

Increase in visual angle subtended by object on the eye by optical means

Ex: Telescopes

A

Angular Magnification

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4
Q

In low vision, we are mainly interested in linear magnification. Linear magnification is the ratio of the image size to object size.

A

Linear Magnification

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5
Q

When an object enters the eye, the image that is being projected on the retina is ________.

Just like magnifiers, when an object is closer, the image that is projected on the retina also becomes ________

A

inverted

bigger

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6
Q

it is defined as tangent of ½ α (alpha) when it is magnified to the tangent of half angle alpha under the reference condition or standard viewing conditions.

A

Magnification (mag.)

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7
Q

The tangent of ½ α (alpha) is equal to half the size of the object divided by ‘I’ the distance of the ____from the lens

A

object

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8
Q

________ is simply making the object large

A

Linear/size magnification

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9
Q

Original height (ho- h small o) at an object distance of / is made _____to object height of h.

A

larger

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10
Q

There is an ___ in size of visual arts from α to α_0

A

increase

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11
Q

Image height ↑ from α_0, to α_m, i.e. it produces a larger __________

A

retinal image

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11
Q

Derivation of Magnification Formula:

A

● Tangent of half the magnified angle divided by the tangent of half the original angle.
● Substituting the definition of tangent into the equation → magnification is the ratio of height of the magnified object over the height of the original object.
● The ratio of the object sizes will give us the magnification produced when an object is made larger, i.e. linear magnification.
● Similar principles and methods can be employed to determine the magnification produced by distance magnification.
● The ratio of the object sizes will give us the magnification produced when an object is made larger, i.e. linear magnification.
● Similar principles and methods can be employed to determine the magnification produced by distance magnification.

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12
Q

Understanding Relative Distance Magnification

A

Object distance changes from a distance | to a new distance /_0

The object size remains the same h=h_0

The visual angle increases from α_0 to α_m

Mag. is ratio of original object distance to closer object distance

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13
Q

USING A HAND MAGNIFIER

A

● Object held at focal point of a lens → image is formed at infinity.
● Light rays emerging out of lens, after refraction are all parallel to one another.
● Individual viewing object through magnifier/lens will not require additional focusing effort.
● Only need distance prescription.

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14
Q

CARE PROCESS IN LOW VISION
(4)

A
  1. PATIENT HISTORY
  2. OCULAR EXAMINATION
  3. SUPPLEMENTAL TESTING
  4. MANAGEMENT OF VISUAL IMPAIRMENT
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15
Q

OCULAR EXAMINATION (5)

A

a. VISUAL ACUITY
b.REFRACTION
c. OCULAR MOTILITY & BINOCULAR VISION ASSESSMENT
d.VISUAL FIELD ASSESSMENT
e.OCULAR HEALTH ASSESSMENT

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16
Q

PATIENT HISTORY REVIEW (5)

A
  1. Ocular History
  2. Visual Functioning
  3. Medical History
  4. Social History
  5. Specific Goals Or Needs
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17
Q

COMPONENTS OF THE PATIENT HISTORY (5)

A

I. OCULAR HISTORY
II. VISUAL FUNCTIONING
III. MEDICAL HISTORY
IV. SOCIAL HISTORY
V. SPECIFIC GOALS OR NEEDS

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18
Q

OCULAR HISTORY

A

● Diagnosis and onset of symptoms
● Past, current, or planned surgeries or treatments
● Stability of vision
● Family history of eye disease
● Previous history of eye disease or vision problems
● Current or previous use of spectacles, contact lenses or low vision aids.
● Patient’s understanding of vision condition and implications for functioning

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19
Q

II. VISUAL FUNCTIONING

A

● Ability to read print and specific reading needs (e.g. bank statements, bills, magazines)
● Other near visual abilities and needs (e.g. writing, sewing, activities of daily living)
● Intermediate visual ability and needs (e.g. use of computer, reading music)
● Distance visual ability and needs
● Independent travel ability and needs (e.g. driving and use of public transportation)
● Photophobia, glare sensitivity, and lighting requirements

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20
Q

III. MEDICAL HISTORY

A

● General health review
● Current medications
● Hearing impairment or other handicapping conditions
● Self-care needs (e.g. ileostomy, diabetes)
● Orthopedic handicaps
● Psychological considerations (e.g. denial, depression, codependency, or suicidal tendencies) - best to refer them

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21
Q

● General health review

A

o Ask general health of the px
o Is the patient Diabetic? Hypertensive?
o Does the patient smoke?

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22
Q

IV. SOCIAL HISTORY

A

● Living arrangements (e.g. lives alone)
o Does the px live alone or does he have any family with him?
● Support systems
● Family interactions
● Employment issues
● Educational concerns
● Recreational concerns

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23
Q

● Educational concerns

A

o Mostly for kids
o Teachers approach doctors

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24
Q

V. SPECIFIC GOALS OR NEEDS

A

● Needs as stated by the patient.
● Needs as determined by the history.
● Needs as identified by the employer, teacher, family, or caregiver
● Realistic patient goals (an ongoing process developing during the course of the examination and exploration of rehabilitation options)

25
Q

Quantifies the degree of high-contrast vision loss, and in many cases, clearly identifies the patient’s visual impairment as it relates to the chief complaint.

A

VISUAL ACUITY

26
Q

Measuring VA also allows you to:

A

⮚ Monitor stability of progression of disease and changes in the visual abilities as rehabilitation progresses.

⮚ Assess eccentric viewing postures and skills, patient motivation, scanning ability (for patients with restricted fields), and in many cases, afford the patient an opportunity to experience
success.

⮚ Teach basic concepts and skills (i.e to
eccentrically view relevant to the rehabilitation process)

27
Q

visual charts samples (3)

A

Feinbloom
Bailey-Lovie
EDTRS

28
Q

For Low Vision Pxs, we do not use_______ we use charts for them.

A

TV or projector

29
Q

Use appropriate testing distances (10 feet, 2 meters, 5 feet, etc.)

A

Usually start at 3 meters. If they can’t do 3m, do 2 meters, then 1 meter. If they still can’t, it means that they no
longer have a distance VA.

30
Q

DISTANCE VISUAL ACUITY MEASUREMENT

A

-Use appropriate vision charts (Feinbloom,Bailey-Lovie, EDTRS, etc.)
-Use appropriate testing distances (10 feet, 2 meters, 5 feet, etc.)
- Evaluate eccentric viewing techniques
-Assess effects of illumination.
- Record measurement of very poor vision as HM, LPP, LP, NLP
-Record distance visual acuity as actual test distance over size of character read.
-Use nonstandard techniques (preferential looking, VEP, edibles, environmental targets,
diagnostic patching, etc) when appropriate.

31
Q

For preverbal kids, use:

A

preferential looking VA test.

32
Q

accurate starting point for subjective
refraction.

A

Autorefraction

33
Q

closer than usual distance (since
some may have media opacities, smaller pupils) can sometimes facilitate detection or neutralization of motion and can be helpful when media opacities are present, pupils are small, or the reflex is dull.

A

Radical retinoscopy

34
Q

may elicit a brighter reflex especially in patients who have high myopia.

A

Off-axis retinoscopy

35
Q

you can look at different axis to see properly and to do what’s easier for you unlike in normal retinoscopy that you have to be eye level with the px.

For low vision px, do the retinoscopy in a trial frame and not in the phoropter

A

Off-axis retinoscopy

36
Q

ASSESSMENT OF SUBJECTIVE REFRACTION

A

⮚ Trial frame, when indicated
⮚ Just Noticeable Difference (JND) technique
⮚ Hand-held Jackson Cross Cylinder
⮚ Nonstandard distances
⮚ Stenopaic slit
⮚ Multiple pinhole lens

37
Q

OCULAR MOTILITY AND BINOCULAR VISION ASSESSMENT (5)

A
  1. Gross Assessment of Ocular Alignment
    - Hirschberg Test
  2. Sensorimotor Testing
  3. Amsler Grid Testing (Mono VS Bino for Eye Dominance)
  4. Contrast Sensitivity (Mono VS Bino for Eye Dominance)
  5. Effects of Lenses, Prisms, or Occlusion on Visual Functioning
38
Q

Evaluate for the presence of nystagmus ocular motility dysfunction (e.g. poor saccades or pursuits), strabismus, substandard binocularity, or diplopia,
which could influence performance or treatment options.

A

OCULAR MOTILITY AND BINOCULAR VISION ASSESSMENT

39
Q

⮚ Visual field integrity may be as important as visual acuity to reading ability.

A

VISUAL FIELD ASSESSMENT

40
Q

⮚ It is a critical factor with respect to independent travel concerns.

A

VISUAL FIELD ASSESSMENT

41
Q

⮚ Measurement of visual field integrity (central, peripheral, or both) should be conducted to determine the presence and location of relative or absolute losses of sensitivity.

A

VISUAL FIELD ASSESSMENT

42
Q

VISUAL FIELD ASSESSMENT INCLUDE: (5)

A
  1. Confrontation Visual Field Testing or Finger Counting Field Testing
    2.Amsler or Threshold Amsler Grid Assessment
  2. Tangent Screen Testing
    4.Goldmann Bowl Perimetry or Equivalent Kinetic Testing
    5.Automatic Static Perimetry
43
Q

FINGER COUNTING FIELD TEST Purpose

A

obtain rough peripheral field assessment without an expensive apparatus; screen for previously unnoted visual field defects.

44
Q

II. AMSLER GRID TEST Purpose

A

● Near point test of central 10 degree of vision
● Determines the position, size, location. and extent of central scotomas.
● Made to test central vision for early signs of macular degeneration.
● Helps develop a program for training in eccentric viewing.

45
Q

SUPPLEMENTAL TESTING (6)
⮚ Contrast Sensitivity
⮚ Glare Testing
⮚ Color Vision Testing
⮚ Visually Evoked Potential (VEP)
⮚ Electroretinogram (ERG)
⮚ Electro-Oculogram (EOG)

A
45
Q

SUPPLEMENTAL TESTING (6)

A

⮚ Contrast Sensitivity
⮚ Glare Testing
⮚ Color Vision Testing
⮚ Visually Evoked Potential (VEP)
⮚ Electroretinogram (ERG)
⮚ Electro-Oculogram (EOG)

46
Q

OCULAR HEALTH ASSESSMENT (4)

A

⮚ External Examination (Adnexa, Lids, Conjunctiva, Cornea, Iris, Lens, And Pupillary Responses)
⮚ Biomicroscopy (Lids, Lashes, Conjunctiva, Tear Film, Cornea, Anterior Chamber, Iris And Lens)
⮚ Tonometry
⮚ Central And Peripheral Fundus Examination With Dilation, Unless Contraindicated

47
Q

DISTANCE of amsler grid test

A

30cm under bright illumination

48
Q

AMSLER GRID TEST Procedure

A

● Must always keep his gaze fixed on the central point during the whole examination with all charts
● Chart must be clearly and evenly lighted
● Avoid the use of all artificial mydriasis, as well as ophthalmoscopy immediately before examination.

49
Q

Good pursuit:

A

smooth, no jerking, no head/body movements

50
Q

Poor pursuit:

A

when px moves their head in order to see the ball/target

*Strabismic px has difficulty following target when conducting full circle technique

51
Q

OBJECTIVE REFRACTION PROCEDURES (6)

A

⮚ Autorefraction
⮚ Standard techniques with trial lenses
⮚ Radical retinoscopy
⮚ Off-axis retinoscopy
⮚ *Near retinoscopy
⮚ *Keratometry or corneal topography to measure anterior corneal curvatures and corneal integrity.

52
Q

this is to measure anterior corneal curvatures and corneal integrity.

A

*Keratometry or corneal topography

53
Q

PROBLEMS WITH PROJECTION CHART
(5)

A
  1. Less Contrast
    - Because in the projector, it is in yellow (not good for LV px)
    2.No acuity level between 20/100 to 20/200,
    between 20/200 to 20/300 and 20/400
    - Because the biggest letter in the Snellen is in 20/200 only
    3.Only one letter for acuity of 20/200 to 20/300 and 20/400.
  2. Presented at 20 feet - which is too far for a distance for many visually impaired patients to maintain fixation.
  3. Projected charts are not recommended for disability determination.
54
Q

● A reduced version of Ferris-Bailey chart, which is calibrated for 40cm (16”) viewing distance.

● Main feature: provides a guide for selecting dioptric power of reading addition based on test results at two test distances.

A

LIGHTHOUSE NEAR TEST CHART

55
Q

MN READ CHART recording

A

RECORDING: 4M @ 40cm

56
Q

The print size and marking on the chart are designed for a testing distance of 40 cm.
- Before you use any chart, take note of the testing distance first.

● Patient should read the text sentence aloud, starting from the top of the chart or from several steps above.

● Patients should continue reading the smaller sizes until they cannot read.

A

MN READ CHART

57
Q

-virtual image formed of objective lens
-Tracing rays from the edge of the objective through the ocular
- → virtual image between the objective and ocular lenses
- = exit pupil in Galilean telescope

A

Galilean telescope

58
Q

-virtual image formed of objective lens
-Tracing rays from the edge of the objective through the ocular
- → virtual image between the objective and ocular lenses
- = exit pupil in Galilean telescope

A

Galilean telescope

59
Q

The ocular lens in a Keplerian telescope forms: (2)

A

o Real image of objective lens
o Image at optical infinity of intermediate image

clinical low vision (2 decks)

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