r-98-39.ppt 483KB Jun 23 2011 12:07:02 PM

Evaluation of a Scanned
Laser Display as an
Alternative Low Vision
Computer Interface
Conor Kleweno, Eric Seibel, Ph.D., Kyle
Kloeckner, Bob Burstein, Erik Viirre, M.D.,
Ph.D., Thomas Furness III., Ph.D.

Problem Statement:

• Can the Virtual Retinal Display (VRD)
be a helpful alternative low vision
computer interface
• A testing protocol is needed to compare
the two interfaces for low vision use

1

Introduction:
• Persons with low vision find computer use difficult with the
standard computer display (CRT)

• A CRT is limited in brightness and contrast
• Low vision aid software can make computer use
cumbersome
• The VRD may be a better alternative for low vision
computer users
• The VRD uses a modulated, low power laser that displays
an image directly onto retina using a two mirror scanning
mechanism

2

Objectives:
• Design a testing protocol to compare the VRD
with a standard computer screen display (CRT)
• Conduct vision tests with low vision subjects
with different low vision conditions
• Determine if the VRD can be an effective
alternative low vision computer interface
• Use an acuity test to compare visual acuity
between the VRD and a CRT

3

Objectives (continued):
• Use a reading speed test to compare reading
performance between the VRD and a CRT
• Determine what types of low vision benefit
from VRD technology
• Have low vision subjects compare the quality
of images displayed between VRD and a CRT
in terms of clarity and brightness

Testing Site Setup:

• Testing conducted in a controlled environment at the
Department of Services for the Blind
• 15 low vision subjects with variety of conditions
4

Four Test Conditions:

• A standard CRT with white on black contrast
• A standard CRT with red on black contrast
• The VRD with red on black contrast with a
luminance setting of one half of the measured
value of the white on black CRT
• The VRD with red on black contrast with a
luminance setting that matches the measured
value of the white on black CRT

5

Procedure:
• CRT acuity test used the white on black contrast
• VRD acuity test used the matched luminance setting
• Reading speed tests conducted at four character
angle sizes
• Three 20 second trials done at each character angle
size
• Subjects given oral questionnaire to obtain
subjective data on clarity and brightness of images

6

Acuity Test:
•Acuity tests conducted using the Landolt ring test
•Pointer arrows were used to assist subject in
locating image
•Acuity test range was 20/1128 to 20/67

7

Reading Speed Tests:
• Three words shown simultaneously to subject on PowerPoint slides
as shown below
• Subject manually advanced through slides and orally read the words
• Unrelated words used
• Reading speed evaluated as correctly read words per 20 second test
• Box placed around words to help subject locate image

bird

her
state

8

Results: Reading Speed
60
40
20
0
-20
-40
-60

All Subjects
Optical Causes
Retinal Causes

Mean Percent Improvement- Matched
Luminance VRD vs. White CRT

Mean Percent (%)

Mean Percent (%)

Mean Percent Improvement1/2 Luminance VRD vs. White CRT

3.15
1.88
1.22
0.74
Character Size in Degrees

-20.00
3.15

1.88

1.22

0.74

Character Size in Degrees

-20
-40
1.88

1.22

0.74

Mean Percent Improvement- Matched
Luminance VRD vs. Red CRT
Mean Percent (%)

Mean Percent (%)

All Subjects
Optical Causes
Retinal Causes

0.00

All Subjects
Optical Causes
Retinal Causes

0

Character Size in Degrees

60.00

20.00

20

3.15

Mean Percent Improvement1/2 Luminance VRD vs. Red CRT

40.00

40

50
40
30
20
10
0
-10
-20

All Subjects
Optical Causes
Retinal Causes

3.15

1.88

1.22

0.74

Character Size in Degrees

9

Did the CRT or VRD Produce
Better Visual Acuity?
Same (3)
CRT (5)

Results:
Visual acuity
Which Display Was Perceptually Clearer?

Subjective responses

CRT (2)

Same (2)

VRD (10)

VRD (6)

Which Display Was Percptually Brighter?
Same (2)

CRT (1)

VRD (11)

10

Discussion:
• VRD increased visual acuity and reading speed in some low vision
subjects
• Overall, subjects with low vision conditions due to optical causes benefited
most from VRD
• 64% of subjects had equal or better visual acuity with the VRD
• 71% of subjects found VRD images clearer
• 79% of subjects found VRD images brighter
• In general, subjects disliked red on black contrast
• The testing protocol allowed a valid comparison between the two displays
• More testing is planned to further define types of low vision that will benefit
from VRD

11

Acknowledgements:
• Human Interface Technology (HIT) Lab
• Howard Hughes Medical Scholar Summer Program
• John Olson and the Washington State Department
of Services for the Blind, Seattle, Washington
• National Science Foundation (Grant number DMI9801294)

12