Lecture 2: visual fields and vision standards Flashcards

1
Q

What happens if you don’t inform DVLA once you become aware of an eye condition which is likely to be a source of danger to the public when driving?

A

-criminal offense
-serious motor insurance implications

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2
Q

How can you tell from somone’s driving licence that they need glasses for driving?

A

01 code on back of driving licence

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3
Q

What are the visual standards for group 1 drivers?

A

-be able to read a registration plate in good daylight with glasses or CL if required

-characters 79mm high and 50mm wide from 20 meters
-VA must be at least 6/12 with both eyes or only one eye is monocular with aids of glasses to CL if required

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4
Q

Is the number plate test reliable?

A

*There is no precise Snellen equivalent to the number plate standard
*If you look at the visual angle, the number plate test is equivalent to 6/15

Latham et al (2014) found:
-people with binocular VA 6/12 could not all pass the number plate test
-some people passed the number plate test but had a VA below 6/12

-different lighting in test room
-weather affects number plate test

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5
Q

What can be done according to Latham et al (2014) to ensure people can read the number plate?

A

-to predict a drivers abiltiy to read the number plate, vision should be assessed using logMAR letter chart or a snellen chart scored by full line

-drivers with 6/7.5 or 6/6 (if there is no 6/7.5 line) or better vision can be advised that they meet the driving standard.

-drivers with VA between 6/9-6/12 should be advised to check their ability to read a nuber-plate as they might not be able to

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6
Q

How should optometrists respond to a patient who asks if their fit to drive?

A

AOP advice: dont provide certificates of ability to pass number plate tests based on consulting room tests

-advise px to statify themselves that they can pass the number plate test alone (at 20m in different weather conditions)

-px can report to licsecing centre who will arrange for the test to be accurately carried out at a driving test centre

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7
Q

When are drivers required to prove their vision meets the standards?

A

every 10 years more frequently as they age

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8
Q

What type of drivers does group 2 include?

What are the visual standards for group 2 drivers?

A

LGV: large good vehicles (lorries)
PCV: passenger carrying vehicles (buses)

-at least 6/7.5 VA in the better eye
-at least 6/60 VA in the worse eye
-Must have a corrective power of less than or equal to +8.00D. No limit for corrective power of contact lenses.

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9
Q

Why are the standards for gorup 2 drivers challenging for optometrists?

A

-not every snellen chart has a 6/7.5 line
-test chart needs to positioned accurately at 6m
-charts at shorter distances but be accurately scaled
-+8.00 refraction limit doesn’t specify if its mean sphere power or highest powered meridian
-hyperopes become more hyperopic as they get older. may start of less than +8.00

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10
Q

What correction should be used when testing fields for driving requirements?

A

habituial correction
binocular telescope in netherlands

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11
Q

What are the visual field requirements for driving?

A

standards are applied when there is evidence that a defect exists:

-minimum field of vision is 120 degrees horizontally
-there should be no significant defect in the binocular field which encroaches within 20 degrees of fixation above or below the meridian
-homonymous or bitemporal defects which come close to fixation are not accepted

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12
Q

What type of visual field testing is used to assess visual requirements?

A

estermen test (supratherehold testing)
-carried out on HFA
-presents a bright stimulus 10dB) at each of the 120 locations
-more than 20% false positives means test is invalid
-carried out at 1/3rd metre
-4 to 5 minutes for the test

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13
Q

What are the disadvantages of esterman?

A

-limited locations of points in the functionally-relevant area of a drivers visual field

-only 34 locations tested in central 20 degrees
-no locations in central 7.5 degrees
-predomiance of central locations are in the lower half of vf (22 vs 12)
-a lot of test points fall on the dashboard (lower vf)
-sensitivity to detect paracentral scotomata is lowest in the upper visual field. This area is particularly relevant when driving

-can only detect the densest scotoma

-fusion difficulties

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14
Q

What defects affecting the central 20 degrees are acceptable for group 1 drivers?

What defects affecting the central 20 degrees are unacceptable for group 1 drivers?

A

-scattered single missed points
-a single cluster of up to 3 contiguous points

-a cluster of 4 or more contiguous points that are either wholly or party within the central 20 degrees area

-loss consisting of a single cluster of 3 contiguous missed points up to and including the 20 degrees fixation area and any additional separate missed points within the central 20 degrees area

-central loss of any size that is an extension of hemianopia or quadrantopia

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15
Q

When can a person reapply for a licence who previously lost it due to failing the visual field rules?

A

-defect has been present for atleast 12 months
-defect was caused by an isolated event or non-progressive condition
-there is no other progressive condition that affects visual fields

-must be a clinical confirmation of full functional adaptation
-if re-application is accepted, applicant must carry out a satidafactory practical driving assessment

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16
Q

When can a driving licence be issued for someone who has a static field defect?

A

-a 3 year provisional licence will be issues if:
-condition is non-progressive
-apllicant has fully adapted to fied defect
-no other relevant medical conditions

-instructor completes a on-road assessment to make sure driver is competent
-if assessment is favorable, a unrestricted provisional licence is issued in the normal way

17
Q

What is disregarded on an estermen test for peripheral defects?

A

-a cluster of up to 3 missed points lying on or across the horizontal meridian

-a vertical defect of only a single point width but of any length which touches or cuts through horizontal meridian

18
Q

What are the visual field requirements for group 2 drivers?

A

-horizontal visual field of atleast 160 degrees
-extension should be at least 70 degrees left and right and 30 degrees up or down
-no defects should be present within a radium of central 30 degrees

19
Q

What are the requirements about diplopia for group 1 drivers?

what are the requirements about diplopia for group 2 drivers?

A

-cease driving on diagnosis

-resume driving on confirmation to the licescing authority that the diplopia is controlled by glasses or by a patch

-exceptionally a stable corrected diplopia of 6 months duration or more may be compatible with driving if there is consultant support indication adaptation

-permanent refusal or revocation if insuperable diplopia
-patching is not acceptable

20
Q

What are the requirments of colour vision for group 1 and group 2 drivers?

A

defective colour vision is no bar to driving

21
Q

What are the conditions for monocular group 1 drivers ?

A

-must inform DVLA if complete loss of an eye
-driving can be resumed after adaptation (driver can satisfy VA, number plstr and vf requirements in remaining eye)

22
Q

What are the requiremnts for monocular group 2 drivers?

A

-complete loss of vision in one eye or corrected acuity of less than 3/60 in one eye means applicants are barred from holding group 2 licence

23
Q

What lighting requirements can lead to stopping a person being issued a driving licence?

A

-px with cataract or refractive surgery may be unable to meet required standards of poor light or glare

-inabilty to see effectively when driving at night with headlights or due to night vision defect (RP)

24
Q

How can blepharospasm affect driving requirements for group 1 and group 2 drivers?

A

-must not drive and inform DVLA

-consultant opinion required. if mild, drivib can be allowed
-control of mild blepharosopasm with Botulinium toxin may be acceptable (no side effects like diplopia)

-DVLA should be informed of any changes or deterioration in condition

-driving not permitted if condition is severe

25
Q

What advice should be given about driving during frames and lenses selection?

A

-limitations of high powered lenses
-danger of wearing tints at dusk or at night
-dangers of transition lenses when entering tunnels and roads shaded by trees

-px with borderline VA should be advised not to drive vehicles with tinted winscreens or tinted lenses

26
Q

How can diabetic retinopathy affect visual field requirements for driving?

A

-pan retinal photocoagulation can cause reduced visual fields
-DVLA will investigate if laser treatment is carried out on both eyes