6 Common misconceptions Optics of deviceUser’s ability to seeBasic use of deviceUse in familiar areas
7 Misconception No. 1 The optical limitations far outweigh the optical advantages of bioptic lenssystems; making such devicesunsafe for use during driving.Slide indicates one of the most common and controversial topics ( namely optical limitations) when it comes to discussion of use of bioptic lens systems for driving. Opponents of bioptic driving past and present adamantly oppose the use of these devices during driving based on professional opinion from stationary points of view vs. results of any applied “hands-on” type of research undertaken under actual on-road dynamic driving conditions.
8 Optical limitations Nearness illusion - Objects or forms appear closer - Depends on level of magnification- In reality, object/form is X times farther away- Jack in-the-box effect
9 “Jack in the box” effect Other road users that suddenly and unexpectedly move into the magnified or non-magnified field of view or path of travelSlide provides a list of the optical limitations which opponents of bioptic lens systems feel make these devices unsafe for driving purposes. The question that arises is “can a person(s) learn to compensate for the above limitations through appropriate training and reinforcement”.
12 Concern of “Jack in the Box” Oncoming, lateral, same directionSudden braking, rear-end accidentsRationale for short fixations
13 Optical limitations (cont’d) Restricted magnified field of view- Dependent on (X) Power, type andsize of telescopic units- Dependent on “vertex distance”
14 Sampling: telescopic fields of view Manufacturer Field of view (degrees)DVI- 2.2X BIO I, BIO II Galilean .……………………. 12, 11- 3.0X WA BIO I; 3X BIO I, 4X BIO I Galilean , 8, 6Ocutech- 1.7X, 2.2X Sight Scope Flip ..………………….. 26, 18- 3.0X Mini …………………………………………. 15- 4X VES –K ……………………………………….. 12Conforma- 4X ½ BITA ....….………………………………….. 8.5
15 Vertex distanceLinear distance or space between center of cornea and center of carrier lens, or center of ocular lens of telescopic unitBioptics are not “horse blinders”
16 Optical limitations (cont’d) Ring scotoma – part of the normal visual scene invisible to the userCreated by the enlarged retinal image produced by telescope (overlaps part of the normal visual image)
17 What photo of “ring scotoma” does not tell you? Scotoma exists for a few milliseconds (intermittent vs. continuous viewing)Extent of non-magnified fieldImpact of 1 vs. 2 telescopes*Source: Randy Jose, O.D., SWOMA Conference
18 Normal visual fieldVisual field of one eye overlaps visual field of other eyeCentral macular vision that is often impaired in bioptic drivers accounts for a small amount of field*Source: Dr. Laura S. Miller, O.D. (ww.nwhillseyecare.com)
19 Optical limitations (cont’d) Apparent movement of visual scene (objects or forms) in opposite direction to head movement- Consistent with all types of devicesthat magnify or enlarge- Rationale for vertical spotting onlySlide provides a list of the optical limitations which opponents of bioptic lens systems feel make these devices unsafe for driving purposes. The question that arises is “can a person(s) learn to compensate for the above limitations through appropriate training and reinforcement”.
20 Apparent movement of object or form opposite to head movement
21 Apparent movement of object or form opposite to head movement
22 Apparent movement of object or form opposite to head movement
23 Optical advantageIncreases “margin of safety” - the time or distance needed to detect and identify a critical object or condition; then predict, decide and execute an appropriate driving maneuver.Slides provide information that supports the use of bioptic lens systems for driving. As alluded to above, if the device is used correctly and as instructed (for detecting and deciphering information or activity at more normal viewing distances versus reliance on driving closer to an object or form before detecting, identifying , deciding to react or not, and then reacting via adjustments in speed or lane position) then the functional benefits of its use during driving become clear and appreciated.
24 Optical advantageAllows bioptic user to detect and identify detail, color and activity of distant objects or forms at farther distances
25 Approach magnification Driving slower and closer to critical object(s) or critical situations before making a decision of what to do or not do
26 Misconception No. 2Low vision drivers depend upon the telescopic portion of their bioptic lens system to see.Slide states a misconception (protraying bioptic lens users as uncorrected near sighted type of individuals like the cartoon character Mr. Magoo) taken verbatim from testimony provided by a former driver licensing official at a legislative meeting who was testifying against the use of bioptics for driving.
27 In realityLow vision drivers can see in the distance, but not distinctly (carrier lens vision).Bioptic lens users can be taught to use functional visual acuity measures (with and without telescopic magnification).This slide sets the stage for the next slide which will introduce and define how all drivers, including trained bioptic drivers use more functional acuity and field of view measures versus reliance on static visual acuity scores to define ways that drivers detect and react to critical objects or conditions in or near their roadway under dynamic conditions. Note the presence of vertex distance in both photos above (linear distance between center of cornea and center of carrier lens or center of ocular lens of telescopic unit). Such space allows a bioptic user to establish and maintain gross awareness of their surroundings even during telescopic fixations. These devices are not constructed nor do they impair side vision like blinders used during horse racing.
28 Functional visual acuity measures Awareness acuity – “I notice something ahead but can’t identify what it is” (gross difference between foreground and background)Identification acuity – “It is beginning to look like a red vehicle” (as driver gets closer to object)Sure acuity – “I definitely recognize it as a red car” (at furthest yet optimal viewing distance)Slide provides information how drivers can began to mentally prepare themselves to react to objects or forms in or nearing their roadway using subnormal visual acuity and visual field cues versus more 20/20 type of detail or clearer viewing at closer distances in driving situations.
33 Misconception No. 3A low vision driver, who is dipping down into the telescopic portion of their bioptic lens system every few seconds or so, is illustrating safe driving practices.
34 In realityDriving is a dynamic task that requires far greater input from the peripheral or side portion of one’s field of view.“If you can’t drive without it, you can’t drive with it”.
35 Why use the telescopic unit? At “critical periods” to increase one’s margin of safety“Margin of safety” defined as - the time or distance needed to detect and react to a critical object or situation
37 Misconception No. 4Low vision drivers need not use bioptics while driving in familiar driving environments.Slide alludes to the misconception that if a bioptic user is familiar with an area or environmental setting he or she is in total control of what may or could happen in that area outside of their vehicle on a daily basis.
38 In realityDrivers have no control over anything that takes place outside of their vehicles- First in line at traffic light (multi-lane crossroad)- road repaving site, water line breaks,tree trimming- First responder(s) at scene of motor vehicleaccidentSlide points out the limitations to which any driver, including a bioptic lens user, is in control of his or her driving environment(s) regardless of how familiar to one’s surroundings. Examples of a few typical unexpected situations that happen in all sorts of driving environments are listed that would encourage a bioptic user to engage his or her device properly and appropriately.
39 First in line at a traffic light Slides provides an example of the benefits of having a bioptic lens system in place when first in line at a series of traffic lights, especially if the latter fixtures are positioned on the far side of multi-lane crossroads.
40 Traffic light with left turn arrow Slide provides an example of the benefits of having a bioptic lens system in place and available for use when first in line in the left turn only lane on approach to a traffic light controlled intersection (or if other small in size regulatory signs are present between or in close proximity to the turn green arrow light indicating allowance to turn or not turn on the turn green arrow only).
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