Transcript Grand Rounds Presentation

Grand Rounds
Case Presentation
Adam Hill
February 5th, 2009
Meet Tom
 27-year-old male
 Applying to be a nuclear security
officer
 History of refractive surgery
 3 years ago
 Thinks it was PRK and not LASIK
 Was moderately nearsighted before
 No visual complaints or other concerns
Nuclear Security Officer
Job Duties
Provide physical protection of facility
Interior and exterior, night and day shifts
Armed!
Preventative foot, vehicle,
stationary patrols
 Search at entry / exit points
 Respond to intrusions, alarms, etc
 Apprehend and detain intruders
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http://www.nuclearsafety.gc.ca/eng/commission/pdf/2008-08-21-Transcript-Meeting.pdf
What do you think
they want from us?
Visual Acuity
 Only makes sense!
 What limit?
 At least the driving standard
 Likely even more strict
 All surveillance activities
highly dependent on
vision for threat detection
Refractive Correction
 Can duties be performed without correction?
 Glasses can fog up, slide off nose, get wet
from rain/snow
 Safety of officer in case of confrontation
 Shatter-resistant lenses, durable frames
 Contact lenses can irritate or dislodge
 Need to consider both UCVA and BCVA
Johnson CA. Occupational psychophysics to establish vision requirements.
Optom Vis Sci. 2008 Oct;85(10):910-23.
Ontario’s Requirements
 Uncorrected VA of 20/40 (6/12)
 Best-corrected VA of 20/20 (6/6)
 That’s with both eyes open
 What if Tom doesn’t make it?
http://www.mcscs.jus.gov.on.ca/english/police_serv/const_select_sys/become_police_const.html
Leave!
 Other
provinces,
RCMP need
20/60 UCVA
 Everywhere
needs 20/20
BCVA, at
least in
one eye.
Hyperopia?
 Ontario and
Alberta are
the strictest
(+2.00D in
least plus
eye)
 Nobody
else cares!
Visual Field
 Needed for driving
 Likely much bigger field required
 Seeing movements during patrol
 Physical surveillance, especially with large
groups of people or vehicles
Ontario’s Requirements
Temporal
Superior
Nasal
Inferior
75º
35º
45º
55º
Sup.Temp
Sup.Nasal
Inf.Nasal
Inf.Temp
40º
35º
35º
70º
 Basically, a full field in all directions.
http://www.mcscs.jus.gov.on.ca/english/police_serv/const_select_sys/become_police_const.html
Huh?
 These criteria sound like they were
determined back when Goldman fields
were the standard of care!
What Test Would You Do?
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
24-2
30-2
Full Field 120pt
Estermann screening
Confrontation
Something else?
In pictures…
This is the minimum field required
In pictures…
24-2 versus required field
In pictures…
“Full Field 120pt” versus required field
In pictures…
Estermann versus required field
In pictures…
FF120 and Estermann
Visual Field
 One option is to do two tests:
 the Full Field 120 point, and
 the monocular Estermann test
 What’s the other option?
Roll Your Own!
Turns out this thing comes with a manual
…and the manual says it’s programmable!
screening test
Quantify defects
(just in case!)
What if Tom’s doesn’t
look this perfect?
No problem!
 Green:
 Horizontal only
 Yellow
 horizontal
plus small
vertical
 Orange:
 full field
Colour Vision
 Fairly standard test for security field
 Important to recognize ID badges,
people, vehicles, identify banned
substances in searches, etc
 Also important for monitoring alarms,
signal lights, etc.
 No defects permitted in any province
Binocularity
 No diplopia!
 No eyestrain!
 Stereopsis
Ontario’s Requirements
 Distance phoria: 5 eso to 5 exo
 Near phoria:
6 eso to 10 exo
 Stereoacuity:
80” of arc
 Lots of people have bigger phorias than
that without having any problems.
 What if Tom doesn’t meet these criteria?
http://www.mcscs.jus.gov.on.ca/english/police_serv/const_select_sys/become_police_const.html
No problem!
 As long as
you still have
two eyeballs,
there’s
somewhere
you can go.
Ocular Health
 Must be healthy!
 Great deal of resources to train staff
 don’t want to hire somebody whose
vision is going to deteriorate with time
 especially if regular eye exams aren’t
required to keep the job!
 Risk of blindness from trauma
 e.g. physical confrontation on-site
 Only a few provinces mention this
specifically
Initial Thoughts
 Many of these tests are part of the
routine battery for a full eye exam
 VA, stereo, cover test, refraction, health…
 We have a visual field machine,
although they don’t specify which test
 What “additional requirements and
specific documentation” do they want
regarding the laser surgery?
Tom’s Examination
 UCVA 20/20 OD, OS, OU
 Refraction:
OD +0.25 -0.50 x 175
20/20
OS plano -0.25 x 180
20/20
 Stereopsis: at least 40” (Stereofly)
 Colour vision: normal (D15)
 Cover test: non-strab, ortho @ ∞
non-strab, 4 exo @ 40cm
Tom’s Examination
 Lids, lashes, conjunctiva healthy
 Cornea clear
 No sign of LASIK scars
 PRK likely the procedure done
 Anterior chamber deep, angles open
 Pupils normal (ERRL)
 IOPs 15mmHg / 16mmHg @ 10:45am
Tom’s
Visual
Fields
Time to breathe!
(And to read the refractive surgery
paperwork he got from his truck!)
Vision Stability
 Only for surgeries within the last year
 No significant change in refraction
or acuity
 “Significant” meaning > 0.50D
or 3 letters on VA
 Two exams at least 3 weeks apart
 Tom doesn’t have to do this part.
Night Vision
 Bailey-Lovie Low Contrast Acuity in Room
Illumination: minimum acuity of 0.20 logMAR
 Bailey-Lovie High Contrast Acuity in Dim
Illumination: minimum acuity of 0.30 logMAR
 Bailey-Lovie Low Contrast Acuity in Dim
Illumination: minimum acuity of 0.58 logMAR
 Tom has to do this part!
 Only need to pass two of the three
20/20
20/32
20/40
20/76
What’s “Dim” Illumination?
 “Illumination on the Bailey-Lovie
Charts ranges from 275 to 350 lux”
 Full lights in the exam room,
paper chart on the wall
 “Dim illumination is created by having
the candidate view the charts through
welding goggles with a Shade 6 filter in
place.”
Dr. Hovis Says
 It’s based on average nighttime brightness
levels for unlit streets
 Required acuities derived from non-surgical
control group performance
 Most people don’t have significant changes
 The ones that do are way off
 > 3 standard deviations away
 These are the people who we need to screen out!
Hovis JK, Ramaswamy S. Visual function of police officers who have undergone
refractive surgery. Am J Ind Med. 2006 Nov;49:885-94.
What Would You Do?
 We might be able to do it, but we
don’t know for sure.
 If we can’t, what’s Tom’s next option?
Looks like quite the drive!
Let’s give him the choice of doing it here,
or travelling 70km to downtown Toronto
The Rest of the Exam
Lens: clear
Vitreous: clear
Macula: healthy
Optic Nerve: 0.2 CD ratio OU;
pink with distinct borders
 Posterior Pole and Periphery:
no pathology noted
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Welding Filters?
“Let’s make that the
intern’s homework!”
In a nutshell…
 It’s incredibly difficult to find a
Shade 6 welding filter.
 It’s even harder to find one with
no notice!
Let’s call the patient!
(To let him know we’re able to do
his night vision tests, of course!)
Procedure
 Three tests:
 Low contrast acuity (room lighting)
 Dim lighting acuity
 Dim lighting + low contrast
 Five minutes are allowed for dark
adaptation (or “goggle adaptation”)
Tom’s Results
 Low Contrast Acuity in Room Illumination:
0.16 logMAR
 minimum required acuity: 0.20 logMAR
 High Contrast Acuity in Dim Illumination:
0.28 logMAR
 minimum required acuity: 0.30 logMAR
 Low Contrast Acuity in Dim Illumination:
0.62 logMAR
 minimum required acuity: 0.58 logMAR
Game Time!
Greg
 18 years old
 Just finished high school
 Ready to join the force
(or ready to apply!)
 Thinks grandpa was
colourblind
Greg
 What would you do?
Linda
 24 year old woman
 Did eye exercises as a child,
unsure of details
 No Rx; VA 20/20
 Non strab;
4 exophoria at dist,
16 exophoria at near
Linda
 What are her options?
 What would you do?
Carl
 32 year old man
 Has glasses, but “only
wears for driving”
 Rx: -1.00 DS OU
 UCVA: 20/50 OU
 BCVA: 20/20
 Everything else:
normal
Carl
 What are his options?
 What would you do?