VF

Question 1

Making the field larger

Answer 1

Expansion

Question 2

Helping the patient use what they have better

Answer 2

Enhancement

Question 3

Mechanisms for VF enhancement

Answer 3

Scanning 
Reversed telescopes 
Fresnel prisms
Mirrors 
Concave lenses

Question 4

Candidates for VF enhancements

Answer 4

• > 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

Question 5

Reversed telescope

Answer 5

• 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

Question 6

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?

Answer 6

5x2. 5=12.5 degrees

100x2. 5=20/250

Question 7

O cute how image minifier

Answer 7

• 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

Question 8

Minus lenses for VF enhancement

Answer 8

• 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

Question 9

Epidemiology of VF defects

Answer 9

VF defections affect 20 to 57% of stroke survivors

-spontaneous improvement may occur for 3 months or sometimes more

Question 10

Hemianopsia

Answer 10

• 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

Question 11

Common complains if hemianopsia

Answer 11

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

Question 12

Recovery of VF defects

Answer 12

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)

Question 13

Fresnel prisms

Answer 13

• 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

Question 14

Fresnel disadvantage

Answer 14

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

Question 15

Fresnel prism for homonymous heminopia field loss

Answer 15

• 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

Question 16

Permanent systems for heminoptic defects

Answer 16

Button prism

Sector prism

Question 17

Peli prism

Answer 17

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

Better for driving

Question 18

Oblique Pelli prism

Answer 18

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

Question 19

Results of peli prism sturdy

Answer 19

• 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%

Question 20

Peli prism demonstration

Answer 20

They make devises to mount to the glasses for demonstration purposes

Question 21

Scanning

Answer 21

• 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

Question 22

Dynavsion scanning training

Answer 22

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

Question 23

Reading for VF enhancement

Answer 23

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

Question 24

Hemineglect

Answer 24

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