bi0ptic telescopes the patient, the decisions, and the training
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Bi0ptic Telescopes The patient, the decisions, and the training. Ian L Bailey, OD, DSc, FAAO School of Optometry University of California, Berkeley. CA 94720-2020 [email protected]. Basic Vision Functions and Driving. Visual acuity reading signs, seeing detail - PowerPoint PPT PresentationTRANSCRIPT
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Bi0ptic TelescopesBi0ptic Telescopes The patient, the decisions, and the trainingThe patient, the decisions, and the training
Ian L Bailey, OD, DSc, FAAOSchool of Optometry
University of California, Berkeley. CA 94720-2020
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Basic Vision Functions and DrivingBasic Vision Functions and Driving
Visual acuityreading signs, seeing detail
Contrast sensitivity seeing larger objects, borders, textures
Visual fields seeing things to the side
Color vision ability to see traffic signals, warning lights
Glare veiling haze from headlights or bright light
Adaptation (light/dark) adjusting to changes in light level
Light sensitivity ability to see in dim conditions
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Should visually impaired people be allowed to drive? Should visually impaired people be allowed to drive? The DilemmaThe Dilemma
For denial to be justifiedEvidence of individual incompetence Evidence (associations) of highly elevated risk Strong prima facie argument for highly elevated risk
Caution when considering statistical evidenceAssociations describe trends - they are not rules
Higher crash rates for a given group is insufficient, by itself, to disqualify all members of that group
Public Safety Risk of accidents, Interference with
traffic flow
Individual's Independence Travel for work, or social participation
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Should visually impaired people be allowed to drive? Should visually impaired people be allowed to drive?
Licensing Authorities (DMV’s) have the responsibility to test driving abilities, to allow or deny licensure,and to impose any restrictions
They may consider Special driving testsPast driving experience Anticipated driving needsCausative disorder Other health issues (sensory, motor, cognitive) They may impose Closer monitoring of driving record More frequent vision and driving tests Restrictions on routes, time of day, etc. Restricted vehicle categories, speed
They may require BiOptic telescopes
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What is the use of BiOptic Telescopes?What is the use of BiOptic Telescopes?
BiOptic telescopes areHead mounted telescopes Typically magnification (for driving) = 2x to 4xArranged to allow easy interchange from viewing with and without the telescope
BiOptic telescopes magnify Enable distant details to been seen to be seen more easily.
Advantages for drivingSigns, signals and other features with more small details can be seen at a longer distance than they otherwise could be
DisadvantagesRing scotoma can reduce field of view Brightness may be reducedHead and/or eye movements are required to interchange
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Vision impairment and NystagmusVision impairment and NystagmusCongential Nystagmus Reduced visual acuity
Normal contrast sensitivity Normal visual fields Astigmatism
Albinism Reduced visual acuityNormal contrast sensitivityNormal visual fields Astigmatism, High refractive error (+) Some sensitivity to light
Achromatopsia Reduced visual acuity Reduced contrast sensitivity (somewhat) Normal visual fields Poor color discrimination Photophobia Astigmatism, High myopia in some (Blue cone)
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Is seeing fine detail important to driving?Is seeing fine detail important to driving?
Yes!Reading signs (freeway signs, street signs, warnings, parking, house numbers, building signs)
Traffic signs size and location usually designed on assumptions that drivers will have a visual acuity of 20/40 (6/ 12 or 0.5)
But!Reading signs, or attending to fine details required for short-term and infrequent driving tasksEspecially in familiar areas, and other situations where need to read signs is minimal
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BiOptic telescopes allow fine details BiOptic telescopes allow fine details to be seen from a longer distanceto be seen from a longer distance
A driver who obtains 20/40 or better through telescope,should be able to read roadway signs, etc., from the intended distance
BiOptic telescopes only engaged intermittentlyBiOptic telescopes only engaged intermittently
for short periods when attending to signs (or other fine detail)
BUTPotential danger when looking through telescope because part of visual field is occluded (RING SCOTOMA)
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Illustration of RING SCOTOMA with 3x telescope Illustration of RING SCOTOMA with 3x telescope
OBJECT SPACE Ring scotoma is blue area blocked by the 3x enlargement of yellow area
IMAGE SPACE 3x enlarged yellow area occludes a substantial area
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A B C D E F G H I J K L M N O
y z a b c d T U V W X 19 20 21 22 y z a b c d
For a 3x telescope Occluded area is 8x larger than the area being magnified
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Projecting a telescope ring scotomaProjecting a telescope ring scotoma
20m = 65 ft 1.8 sec @ 40 km/hr (25 mph) 0.7 sec @ 100 km/hr (63 mph)
3x 3x
Keplerian GalileanREAL WORLD Object space
SUBJECT SEES Image space
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Ring scotoma could be hazardousRing scotoma could be hazardous
When viewing through telescope. There must be a substantial para-central field loss from the ring scotoma,
IF -- the second eye is occluded OR -- if the second eye is functionally blind
OR -- if there is a binocular telescope system
BUTWhen viewing through telescope, there is no field lossProvided -- second eye does not have a telescope
remains open can readily detect large peripheral objects
does not have profound suppression
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Some visual criteria for selecting patients Some visual criteria for selecting patients for BiOptic Telescopes for drivingfor BiOptic Telescopes for driving
Best corrected Visual Acuity - 20/160 to 20/50 range (6/48 to 6/15)
Telescope V A (M= 4x or less) - 20/40 to 20/32 range (6/12 to 6/9.5)
Should not have more than a 3x (0.5 log units) reduction in CS
Should not have significant field defects
Telescope before one eye only (better reading eye)
Second eye should have VA of 20/400 or better (6/120)
Second eye should not have profound suppression
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Before prescribingBefore prescribingOptometric consideration of visual abilitiesOptometric consideration of visual abilities
Hard numbers on Visual acuity Contrast sensitivity
Visual fields
Evaluate as needed Color vision Glare
Adaptation (light/dark) Light sensitivity
Consider Motor and mental agility Reaction timeVision in clutterDivided attention
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Some variations on usual more common testsSome variations on usual more common tests Visual Acuity Visual Acuity Reading efficiency for words and sentencesReading efficiency for words and sentences
pretty only loves side along visits cold months smiled part ride about begins work today ready called draw tired jump
Put your first name on this paper if you will help tomorrowMany people came to help us clean the place after the party
Word Reading10 words each sizeGrade 3 word lists
Sentences60 charactersMNRead
10 M8.06.35.04.03.22.52.01.61.251.00.80.630.50.40.320.250.2
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Some variations on usual more common testsSome variations on usual more common tests Visual FieldsVisual Fields Effect of illuminationEffect of illumination
Variable luminance backgrounds
EITHER Plot fields
OR Ask about letters visible on chartat different luminances
RP, ARM etc fields change with luminance
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Some variations on usual more common testsSome variations on usual more common tests Contrast SensitivityContrast Sensitivity Response Efficiency TestsResponse Efficiency Tests
Number search Flashing squares
Output display Less than 2 mins per testResponse time 2 measures at 24
contrasts vs Log CS
1.81.61.41.21.00.80.60.40.20.00
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2
3
log CS
Res
pons
e (s
ecs)
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5
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Some variations on usual more common testsSome variations on usual more common tests Useful Field of ViewUseful Field of View (UFOV)(UFOV)
Test patient’s ability to respond to peripheral stimuli
Delayed reaction times for peripheral visual stimuli
Failure to see brief, peripheral visual stimuli (i.e., reduced measured visual field)
When there is Divided visual attention Visual clutter Multi-tasking
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Before prescribingBefore prescribingEnsure good skill using telescopesEnsure good skill using telescopes
Hand held telescope - magnification equal to, or stronger, than planned bioptic
Achieve 20/40 with telescope
Efficient spot viewing - both indoors and outdoorsstationary observer - stationary object of regardstationary observer - moving object of regardmoving observer - stationary object of regardmoving observer - moving object of regard
Real world location and viewing of targets in visual clutterfirst locate the target object, and then engage telescope
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Before prescribingBefore prescribing Advising the patientAdvising the patient
Advise patients about their visual disabilities and functional relevance
Bioptic telescope does not ensure ability to pass driving testBioptic telescopes do not restore vision to normalEven with bioptic telescopes, they remain at a visual disadvantage
Need to drive with extra cautionShould have companion drive when possible
Need practice in viewing with bioptic telescope systemNeed supervised training using bioptic telescope for driving
If no driving experience, likely to need more instruction than usual from a professional driving instructor
The DMV makes the final decisions
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Prescribing BiOptic TelescopesPrescribing BiOptic Telescopes
• Select telescope Magnification Design (Designs for Vision, Ocutech)
Galilean, smaller, light weight, small field
Keplerian, longer, heavier, larger field
Focus fixed, adjustable, auto
Exit Pupil smaller or larger than pupil
• Select frame Suitable for telescope mounting Sturdy and comfortable Adjustable to vary height, lateral position and angle
• Determine lens powers for telescope and carrier lens • Select characteristics of carrier lens (SV, bifocal, tint)
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PrescribingPrescribingPositioning Positioning && Angling Angling BiOptic TelescopesBiOptic Telescopes
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Training: Training: Using a BiOptic TelescopeUsing a BiOptic Telescope
Rehabilitation Staff Five to fifteen lessons of 30 minutes. Home practice after each lesson Begin practice indoors with flash cards, Practice outdoors while walking (include traffic signs)
Practice while a passenger in a car residential, business and freeways(locate signs, signals, landmarks and then engage telescope)
WHEN patient is proficient with telescope while a passengerTHEN we issue DMV report form, patient applies for permit AND patient begins training with professional driving instructor
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TrainingTraining
Test Cards Test Cards for bioptic telescope evaluationsfor bioptic telescope evaluations
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Dealing with theDealing with the Department of Motor VehiclesDepartment of Motor Vehicles
• Appointment with a “Driver Safety Referee”• Present vision report that includes information
VA with and without telescopeFields, contrast sensitivityCausative eye disease or disorder, stability and prognosis
May be considered a learner’s permit
THEN the patient takes the written test THEN driving permit may be issued
LATER, patient takes drive test
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Department of Motor VehiclesDepartment of Motor Vehicles Driving test Driving test
Driving test appointment with a “Driver Safety Referee”
Driving test Longer course than usualExposure to more visually-demanding driving tasks
Night time drive test may be requested if patient wants to remove “no night driving” restriction
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Department of Motor VehiclesDepartment of Motor Vehicles Issue of a Driving License Issue of a Driving License
Unrestricted or Restricted License??Special considerations Driving skill tests Causal disease
Driving experience Visual abilitiesDriving record Extent of vision lossDriving need Prognosis, stabilityAnticipated driving Variability of vision Sensory motor disabilities Other visual disabilities
Special constraints Monitor Accidents ViolationsIncrease frequency Renewal Vision reportsDriving testsRestrict Time of day Visibility conditions Routes PurposeDistance from home Vehicle categoryRequire BiOptic Telescope Special mirrors
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Some ConclusionsSome Conclusions
Visual acuity tasks much less important than visual field and contrast sensitivity tasks
BiOptic Telescopes enable seeing of finer detail, when needed
Visually impaired drivers should be given opportunity to demonstrate ability to drive safely
It can be reasonable to specify definite limits OPINIONS :New California limit -better than 20/200 (6/60) -is acceptable
No driving with hemianopia is reasonable
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For EuropeFor EuropePOLICIES TO DEMAND BiOptic telescope is a corrective lens system Telescope must allow visual acuity of 6/12 (20/40 or 0.5)
Telescope must be before one eye only BiOptics are to be used with two eyes open so, relevant visual field test is with both eyes open
COMPROMISES TO ACCEPT OR CONCEDE Vision report every 5 years (at least) Maximum mag = 4x, or without TS, VA > 6/48 (20/160 or 0.125)
Driving should be conditional on wearing telescope Initial license should be for daytime use only Night driving cannot be considered until 3 years experience