“I can see clearly now!” - iaasm.org · Cleared, 88PA, Case # 2017-241, 24 Jun 2017 USAF Operational Based Vision Assessment (OBVA) Lab “I can see clearly now!”

Cleared, 88PA, Case # 2017-241, 24 Jun 2017

USAF Operational Based Vision Assessment (OBVA) Lab

“I can see clearly now!”

I n t e g r i t y - S e r v i c e - E x c e l l e n c e

Headquarters U.S. Air Force

OBVA Color Cone Contrast TestHigh Definition (CCT-HD)

Research & Development

Steven C Hadley MD, FACSColonel (Ret), USAF, MC, CFS

Command Pilot-PhysicianChief, OBVA lab

Aerospace Ophthalmology Consultant to USAF Surgeon General Asst. Professor of Surgery, USUHS School of Medicine

12 Sep 2017


CCT-HD Research & Development65th ICASM 2017 Rome, Italy

OBVA Laboratory711 HPW/FHOH

Steven Hadley, MD1

Marc Winterbottom, PhD1

James Gaska, PhD1

Logan Williams, PhD1

Steven Wright, OD1

Charles Lloyd, PhD2

1711 HPW/USAFSAM2Visual Performance LLC

Integrity Service Excellence

711 HPW/USAFSAM


• The views expressed are those of the author and do not necessarily reflect the official policy or position of the U.S. Air Force, the Department of Defense, or the U.S. Government

• This work was supported by U.S. Air Force contract FA8650-12-D-6280 to Wyle Laboratories and was funded by the 711 HPW/USAFSAM

• There are no off label use of medications discussed

Disclaimer

Cleared, 88PA, Case # 201x-xxxx, xx Mon 201x.


OBVA High-Bay “Vanderbeek Dome”

• Barco Sim10 Projectors: 150M pixels

• Scalable warping and blending


OBVA Laboratory Research

OBVA KC-46 remote vision system simulation. Photo by USAFSAM media department.

OBVA high-bay simulation facility. CAD drawing generated by OBVA personnel.

F-35 HMDS. Source: DIMOC.

Unmanned aerial vehicle ground control station color

displays. Source: DIMOC.

Simulated color-coded situation awareness display. OBVA Lab image.


Operational Based Vision Assessment (OBVA) Laboratory

• Using simulation environment & laboratory vision tests:

– Provide quantitative data defining visual performance capability that will prove useful during air combat, contribute to success of the mission, and help ensure survivability

– Operational based vision standards and waiver criteria

– Evaluate correction, enhancement, protective technologies

– Uncover strategies (training, engineering) to improve vision performance and possibly counter deficiencies

– Establish platform-specific vision standards

– Modernize aircrew vision screening


“A color defective who, for reasons of his own, hides his defect might do well, but a color defective who insists that he ‘knows all colors,’ that he is ‘perfectly o.k.’ is a menace. Of course, he sees all colors in his own way and in his own way ‘knows all colors’ – all his colors. But he must realize that he sees them not the way the rest of us see them, that we are in the majority and that tests, traffic lights, neckties, decorating schemes, wire codes were made to serve us, not him.” Arthur Linksz, MD “An Essay on Color Vision”

Where it startedFlight Environment Demands - Color Vision

Used with permission Douglas J. Ivan, MD; USAF COLOR VISION TESTING STRATEGY AND METHODOLOGY AsMA COLOR VISION WORKSHOP, 2007




Displays- Past, Present and FutureIncreasingly Color-Demanding Environment

P-51 KC-135R/T

F-35






Motivation for OBVA research

Chart on front door of

F-35 flight surgeon

office in a USAF flying

squadron.

Photo by Dr Steven Hadley

Motivation for OBVA research “To insure the USAF vision tests are

predictive of operational performance,

operationally accurate and precise, while

providing reproducible results for

qualification, standards and policy

decisions”

Steven Hadley MD, USAF Pilot-Physician (retired), Chief USAFSAM/OBVA

SCAMMING PIPsColor Vision Caper – 1994


PIP I PIP II PIP III F2

96% 78% 65% 88%

PIP I Sensitivity

Percent of Color Defectives That Fail TestPIP I Passing Criterion: 12 of 14 correct

USAF Pilots & Aircrew (n=1329)

PIP I PIP II PIP III F2

78% 47% 53% 76%

USAF Pilots Applicants (n=1279)

Fail to detect 22%!


Previous Available Color Tests

• Historically, color vision assessed using:

– Color plates, hidden images

– Arrangement of colored caps

– Color matching

– Lanterns

• Numerous limitations:

– “Test preparation”

– Plates fade over time

– Special lighting required

– Reliability

– All lanterns allow CVD to pass


Introduction

All USAF pilot candidates required to

pass strict color vision standard to

maintain flight safety– No color deficiency allowed

– US Army and US Navy permits mild to

moderate color deficiency

– Commercial airlines, most other Air Forces

effectively permit mild deficiency

In 2011, the USAF introduced a new

computer-based color vision

screening test - the Rabin cone

contrast test (RCCT)– Replace pseudoisochromatic plate (PIP) tests

– Demonstrated to very reliably screen for color

deficiency (Rabin et al, 2011; Hovis, 2016)

Dvorine PIP test. OBVA Lab photo.

Rabin CCT L, M cone test letters. OBVA Lab image.


Color Testing: Rabin CCT

• Validated against

anomaloscope

– 92 normal (CVN),

47 deficient (CVD)

– Rabin, Gooch, &

Ivan (2011)

• Well suited for

clinical application


Cone Isolation Technology

• Selectively stimulates:

– L-cone: Red

– M-cone: Green

– S-cone populations: Blue

•Negligible responses from non-

targeted cone populations

decreasing contamination


Team Aerospace Begins Here!

N

V

R

E

U

ZZ

Automated CCT Single letter

presentation

Different (random)

sequence each time

CCT validated against anomaloscope. Can ID CVD anomaloscope may miss

Very effective at identifying, classifying color deficiency

Huge advancement over previous standard (PIP plates)

Color Testing: Rabin CCT

Extremely sensitive and specific to identify color normal and quantify color deficiency


1. Single subject identified color deficient by anomaloscope; however, all other testing identified subject as normal.

2. Single subject identified as color normal by anomaloscope; however, all other testing identified as color deficient.

3. 17 subjects additionally identified as having a Tritan (Blue cone) defect, not confirmed on any other testing.

Cone ContrastTest

(CCT Staircase)

Colour Assessment and Diagnosis (CAD)

Computerized Color Vision Test

(CCVT)

Oculus Anomaloscope

Subjects evaluated98 Total Subjects

48 Color Normal, 50 Color Deficient (based on test battery)*

Sensitivity(Color deficiency correctly diagnosed)

100.0%(50/50)

100.0%(50/50)

96.0%(48/50)

96.0%(48/50)

Specificity(Normal color vision correctly diagnosed)

100.0%(50/50)

100.0%(50/50)

96.0%(48/50)

98.0%(49/50)

Nature of deficiency correctly diagnosed (i.e. deutan vs. protan)

100.0%(50/50)

94.0%(47/50)

78.0%(39/50)

96.0%(48/50)

Wright et al “Comparison of Digital Color Vision Tests” AsMA 2015


Rabin CCT - Negatives

Interface is poor, slow, introduces luminance changes

Bailey-Lovey letters accepted, but introduces

variability, problematic response method

Display chromaticity dependent on viewing angle

–Testers can move head around to improve score

Does not produce reliable results in low normal/mild

CVD (mCVD at 12 test points has +/- 18 points-terrible

test/retest reliability)

–Test-retest reliability a problem for borderline CD

Color calibration works but is limited to 5 contrast

levels

Ceiling effect: Historically almost all normal measure

100 (80% male; 95% female)


OBVA CCT-HD

To support USAF, more precise color test needed

– Operational Based Vision Assessment (OBVA) Cone Contrast Test

(CCT-HD)

• Described in previous report (Gaska et al, AsMA 2016)

– IPS (in-plane switching)

– Precise calibration to obtain lower contrast, 0.25% cone contrast

steps

• Spectraradiometer (Maya 2000 Pro, Ocean Optics)

• CIE 2006 LMS functions

– Landolt C optotype, 4 AFC to reduce response variability

– Well-accepted adaptive threshold procedure (Kingdom & Prins,

2010)

– Photopic adapting luminance


In Plane Switching (IPS)

Low Sensitivity to Viewing Angle

IPS LCD displays

provide limited

changes in

brightness and color

irrespective of the

viewing angle

Directional stability

critical to produce

accurate low

contrast cone

isolation, without

which, precision of

testing may suffer


CCT-HD Improvements over RCCT

Current implemented improvements–Vastly reduced color shifts via IPS / PLS display

technology

– Improved sensitivity through unique calibration

techniques (custom curves and dithering pixel shader)

–Built on well understood and peer-reviewed

psychophysical methods. (Psi, Quest, UpDown

Staircase, Method of constant stimuli)

–Removed the variability in difficulty across trials by

using a single (mostly) spherically symmetric optotype

(Landolt C).

–Removed the need for the subject to look away from

stimulus location in-between trials.


CCT-HD Cone Isolation Technology

• Derived from a series of

complex calculations to

create specific target and

background colors of

declining contrast

•Displayed on selected

monitor / graphics card

systems with …

•Advanced calibration for:

•precision color rendition

•minimal luminance cues


CCT-HD Design Criteria

•Detect abnormalities and

characterize the contrast

sensitivity of both the

color and achromatic

mechanisms of the human

vision system

•Increase the reliability and

efficiency of these metrics

widely used in medical and

occupational environments


CCT-HD Evaluation, Normative Data

USAF Flying Class I (FCI)

pilot candidates were tested

using the CCT-HD and Rabin

CCT (RCCT) during their

medical pilot screening

Administered CCT-HD either

binocularly or monocularly

Some participants repeated

the test to examine test-

retest reliability

Approximately 1,100-2,200

FCI candidates tested


Rabin CCT Distribution (OD, OS)

RCCT distribution

– Monocular scores (0 – 100)

Approx. 80% of FCI

candidates score 100

L-cone: 2,182 eyes tested

M-cone: 2,168 eyes tested

CVN Mean, SD

– L: 97.2, 4.2

– M: 97.7, 3.8

Protans: 0.92%

Deutans: 3.8%


CCT-HD Distribution (OD, OS)

CCT-HD distribution

– Monocular log contrast

sensitivity

Sensitivity of CVN

individuals revealed with

CCT-HD

L-cone: 1,091 eyes

M-Cone: 1,084 eyes

CVN Mean, SD

– RCCT Criterion: 1.65

– L: 2.08 (0.83%), 0.11

– M: 2.02 (0.96%), 0.10

Protans: 0.73%

Deutans: 3.8%

3.7 SD


CCT-HD Distribution (OU)

CCT-HD distribution

– Binocular log contrast

sensitivity

– Binocular testing not

possible with RCCT

L-cone: N = 499

M-Cone: N = 500

CVN OU Mean, SD

– RCCT Criterion: 1.65 +

0.15 (binocular

summation)

– L: 2.21 (0.62%), 0.11

– M: 2.15 (0.70%), 0.10

– Binocular summation

• Log 0.13 = 1.36

3.5 SD


Benefit of CCT-HD -- No Ceiling Effect• M cone test results distribution• The bottom horizontal axis identifies contrast sensitivity and the top horizontal axis shows the

equivalent CCT scores. • The pass/fail criterion (1.65 logCS, 75 CCT score) is shown by the solid line.• The maximum measurable contrast sensitivity in for the RCCT ( 1.9 logCS, 100 CCT score) is

shown using the dotted line.• Contrast Sensitivity values to the right of the dotted line (~ 86% of normal observers) cannot

be measured using the RCCT

RCCT scores all these results at 100% due to ceiling effect

CCT-HD Distribution (OU)


RCCT Test-Retest (OD vs. OS)

N = 1,091N = 1,098


CCT-HD Test-Retest

N = 81

N = 79

N = 77

N = 76


OBVA Collaborative R&D

International, industry, academic (and tri-service?) collaboration

– Enhanced mutual reliance, cost sharing, augmented data collection

– Technology transition and development


Conclusions

CCT-HD provides capability to characterize color

sensitivity for normal/supranormal individuals

Enables binocular testing

Improved reliability

Enables OBVA research examining relationship between

color vision and operational performance– Color-coded displays

– PAPI light identification

– UAV GCS color coded displays

Enable USAF to obtain baseline color vision data to

support human performance optimization, earlier

diagnosis of disease/injury– Meet new requirements by AF/SG and Major Commands (AETC, ACC)


KC-46A refueling F-35A

Steven C Hadley MD, Chief, OBVA lab; USAF Surgeon General Consultant for Aerospace [email protected] or [email protected]

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“I can see clearly now!” - iaasm.org · Cleared, 88PA, Case # 2017-241, 24 Jun 2017 USAF Operational Based Vision Assessment (OBVA) Lab “I can see clearly now!”