2010 BC Guide in Determining Fitness to Drive
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2010 BC Guide in Determining Fitness to Drive

2010 BC Guide in Determining Fitness to Drive 2010 BC Guide in Determining Fitness to Drive

pssg.gov.bc.ca
from pssg.gov.bc.ca More from this publisher
13.07.2015 Views

21.20 Recommended procedures for testing visual functionsVisual acuityThe distance visual acuity of applicants should be tested using the refractive correction(spectacles or contact lenses) that they will use for driving. The examiner should assess visualacuity under binocular (both eyes open) or monocular conditions if required by the standard. It isrecommended that visual acuity be assessed using a Snellen chart or equivalent at the distanceappropriate for the chart under bright photopic lighting conditions of 275 to 375 lux (or greaterthan 80 candelas/m2). Charts that are designed to be used at 3 meters or greater arerecommended.Visual fieldWhen a confrontational field assessment is carried out to screen for visual field defects thefollowing procedure is recommended as a minimum:1. The examiner is standing or seated approximately 0.6 m (2 feet) in front of the examineewith eyes at about the same level.2. The examiner asks the examinee to fixate on the nose of the examiner with both eyesopen.3. The examiner extends his or her arms forward, positioning the hands halfway betweenthe examinee and the examiner. With arms fully extended, the examiner asks theexaminee to confirm when a moving finger is detected.4. The examiner should confirm that the ability to detect the moving finger is continuouslypresent throughout the area specified in the applicable visual field standard. Testing isrecommended in an area of at least 180° horizontal and 40° vertical, centred aroundfixation.If a defect is detected, the individual should be referred to an ophthalmologist or optometrist fora full assessment.When a full assessment is required, the following techniques are acceptable:1. Goldmann III/4e and V4e isopters2. Humphrey Esterman test3. Humphrey 81, 120, 135, or 246 point screener. Set test strategy to single intensity or 3zone and all other parameters to standard. Two zone Humphrey testing is inadequate.4. Medmont 700 Driving Field5. Other visual field techniques will be accepted if appropriate.286

Please note:Goldman, Esterman and Humphrey 135 are the only tests that will test 150 degreesof horizontal vision as required for professional (class 1 to 4) drivers.Binocular testing is always preferred. If a monocular test of the type noted above isavailable from the patient’s file, it may suffice, but if the driver requires new fieldtesting, please request binocular fields.Some automated testing devices used in driver testing centres have a procedure for assessingvisual field. However, these tests are often insensitive to many types of visual field defects andthus may not be adequate for screening purposes.DiplopiaAny patient reporting double vision should be referred to an ophthalmologist or optometrist forfurther assessment.Contrast sensitivityAssessment of contrast sensitivity is recommended for applicants referred to an ophthalmologistor optometrist for vision problems related to driving. Contrast sensitivity may be a more valuableindicator of visual performance in driving than Snellen acuity. The COS therefore encouragesincreased use of this test as a supplement to visual acuity assessment.Contrast sensitivity can be measured by means of several commercially available instruments:the Pelli-Robson letter contrast sensitivity chart; either the 25% or the 11% Regan low-contrastacuity chart; the Bailey-Lovie low-contrast acuity chart or the VisTech contrast sensitivity test.The testing procedures and conditions recommended for the specific test used should befollowed.Depth perceptionThere are no clinical tests available for assessing depth perception other than those used forstereopsis. If stereopsis assessment is required, the Titmus test can be used.Dark adaptation and glare recoveryCurrently there are no standardized tests or procedures that can be recommended for assessingthese functions.287

21.20 Recommended procedures for test<strong>in</strong>g visual functionsVisual acuityThe distance visual acuity of applicants should be tested us<strong>in</strong>g the refractive correction(spectacles or contact lenses) that they will use for driv<strong>in</strong>g. The exam<strong>in</strong>er should assess visualacuity under b<strong>in</strong>ocular (both eyes open) or monocular conditions if required by the standard. It isrecommended that visual acuity be assessed us<strong>in</strong>g a Snellen chart or equivalent at the distanceappropriate for the chart under bright pho<strong>to</strong>pic light<strong>in</strong>g conditions of 275 <strong>to</strong> 375 lux (or greaterthan 80 candelas/m2). Charts that are designed <strong>to</strong> be used at 3 meters or greater arerecommended.Visual fieldWhen a confrontational field assessment is carried out <strong>to</strong> screen for visual field defects thefollow<strong>in</strong>g procedure is recommended as a m<strong>in</strong>imum:1. The exam<strong>in</strong>er is stand<strong>in</strong>g or seated approximately 0.6 m (2 feet) <strong>in</strong> front of the exam<strong>in</strong>eewith eyes at about the same level.2. The exam<strong>in</strong>er asks the exam<strong>in</strong>ee <strong>to</strong> fixate on the nose of the exam<strong>in</strong>er with both eyesopen.3. The exam<strong>in</strong>er extends his or her arms forward, position<strong>in</strong>g the hands halfway betweenthe exam<strong>in</strong>ee and the exam<strong>in</strong>er. With arms fully extended, the exam<strong>in</strong>er asks theexam<strong>in</strong>ee <strong>to</strong> confirm when a mov<strong>in</strong>g f<strong>in</strong>ger is detected.4. The exam<strong>in</strong>er should confirm that the ability <strong>to</strong> detect the mov<strong>in</strong>g f<strong>in</strong>ger is cont<strong>in</strong>uouslypresent throughout the area specified <strong>in</strong> the applicable visual field standard. Test<strong>in</strong>g isrecommended <strong>in</strong> an area of at least 180° horizontal and 40° vertical, centred aroundfixation.If a defect is detected, the <strong>in</strong>dividual should be referred <strong>to</strong> an ophthalmologist or op<strong>to</strong>metrist fora full assessment.When a full assessment is required, the follow<strong>in</strong>g techniques are acceptable:1. Goldmann III/4e and V4e isopters2. Humphrey Esterman test3. Humphrey 81, 120, 135, or 246 po<strong>in</strong>t screener. Set test strategy <strong>to</strong> s<strong>in</strong>gle <strong>in</strong>tensity or 3zone and all other parameters <strong>to</strong> standard. Two zone Humphrey test<strong>in</strong>g is <strong>in</strong>adequate.4. Medmont 700 Driv<strong>in</strong>g Field5. Other visual field techniques will be accepted if appropriate.286

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