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3F: Low Vision > VF > Flashcards

VF Flashcards

1
Q

Making the field larger

A

Expansion

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2
Q

Helping the patient use what they have better

A

Enhancement

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3
Q

Mechanisms for VF enhancement

A 
Scanning 
Reversed telescopes 
Fresnel prisms
Mirrors 
Concave lenses
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4
Q

Candidates for VF enhancements

A
  • > 20 degrees generally do not rewuire special assistive devices, but could potentially use orientation and mobility evaluation
  • 10 degrees-define mobility evaluation
  • 5-10 degrees may use up 10x magnification if they have good scanning skills
  • <5 degrees will rewuire special training, especially mobility skills
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5
Q

Reversed telescope

A
  • apparent increase in FOV approximately equal to the pier of the telescope
  • image is minified by approximately the same amount
  • spectacle mounted vs hand held
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6
Q

Patients BCVA is 20/100. VF is 5 degrees in widest diameter. What size field would you anticipate with a 2.5x galilean hang held telescope used for field enhancement? what VA would you expect when used for visual field enhancement?

A

5x2. 5=12.5 degrees

100x2. 5=20/250

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7
Q

O cute how image minifier

A
  • crisp, undistorted, flat field
  • wide ocular lens permits scanning through device
  • 50% field enhancement effect (0.5x)
  • spectacle mounted, or handheld with neck strap
  • adjustable focus allows optimum focus for each patient
  • huge depth of field
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8
Q

Minus lenses for VF enhancement

A
  • essentially creates a reverse Galilean telescope
  • pateitnt must accommodative or use add to use it
  • order lens blanks form the optical lab and have edges polished
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9
Q

Epidemiology of VF defects

A

VF defections affect 20 to 57% of stroke survivors

-spontaneous improvement may occur for 3 months or sometimes more

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10
Q

Hemianopsia

A
  • lesion in visual pathway leading to VF deficit
  • patients often do not undersdetand that they have lost vision in both eyes, they associate the loss with the eyes on the side of the field loss
  • right hemispheric strokes often associated with visuo-spatial neglect
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11
Q

Common complains if hemianopsia

A
  • bumping into things on affected side
  • difficult with depth preception
  • difficulty reading
  • desire to drive
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12
Q

Recovery of VF defects

A

Can occur for up to a year, but the majority of recovery occurs in the 1st 1-2 months
-recovery of visuo-spatial neglect may take longer (up to 12 weeks)

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13
Q

Fresnel prisms

A
  • goal: move image of an object from patient’s non seeing area closer to the functional viewing area
  • prism usually of 15-25 PD range
  • temporary-patient May remove later
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14
Q

Fresnel disadvantage

A
  • image jump
  • image degradation
  • chromatic aberration
  • more noticeable for higher power PD
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15
Q

Fresnel prism for homonymous heminopia field loss

A
  • apply 15-25 PD to the eye on the side of the field loss, i.e. left loss-prism on left eye
  • base of prism foes in the direction of the field loss, left loss-prism base left
  • split the pupil with the edge of the prism to start
  • as the patient develops their scanning abilities, the nasal edge of the prism will be moved more temporally
  • ultimately, the patient will no longer need the prism
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16
Q

Permanent systems for heminoptic defects

A

Button prism

Sector prism

17
Q

Peli prism

A

Fit them on the upper and lower edge of the iris.

Better for driving

18
Q

Oblique Pelli prism

A

Gives more expanded central vision than the other types o prism. Can’t see out quite as far but still better to have central vision

19
Q

Results of peli prism sturdy

A
  • a signification higher proportion said yes to real than sham prisms
  • at the end of the crossover, 61% continued prism wear in oblique group and 60% in the horizontal group
  • those who continued wear after 6 months reporters grater improvement in mobility with real than sham prisms at crossover end
  • participant who discontinued wear reported no difference
  • at the long term interview, 36% and 47% were still wearing the prism glasses in each group, respectively
  • overall continuation rate at 6m months was 41%
20
Q

Peli prism demonstration

A

They make devises to mount to the glasses for demonstration purposes

21
Q

Scanning

A
  • requires coordinated efforts of head and eyes to develop a systematic search for objects in tje envrinmooent
  • typically taught by OT or O and M
22
Q

Dynavsion scanning training

A
  • trains systematic strategy
  • also works on dual attention skills
  • similar to a lot of sports vision reactions training
23
Q

Reading for VF enhancement

A
  • Use line guide
  • draw colored line at end of the text on affects side
  • turn Paige sideways and read vertically
  • read upside down
24
Q

Hemineglect

A
  • occurs mostly with right parietal lobe CVA
  • may or may not have concurrent hemianopsia
  • often also have attention deficits

3F: Low Vision (16 decks)

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