Development of a System to Study the Impact of Headlight Glare in a Driving Simulator

We report on the development of a realistic dynamic simulation of oncoming headlamp glare in a driving simulator. To our knowledge, no such simulation had been attempted or achieved previously. The simulation is based on superposition of a bright LED display through a beam splitter on the simulator screen and synchronizing the illuminated LED position to the image of the simulated oncoming car. LED brightness is adjusted to result in the level of light that such headlights would cause in the driver’s eyes, enabling the testing of glare effect on drivers of different ages and impact (reduction or increase) of various vision devices

Aniseikonia tests: The role of viewing mode, response bias, and size-color illusions.

PURPOSE To identify the factors responsible for the poor validity of the most common aniseikonia tests, which involve size comparisons of red-green stimuli presented haploscopically. METHODS Aniseikonia was induced by afocal size lenses placed before one eye. Observers compared the sizes of semicircles presented haploscopically via color filters. The main factor under study was viewing mode (free viewing versus short presentations under central fixation). To eliminate response bias, a three-response format allowed observers to respond if the left, the right, or neither semicircle appeared larger than the other. To control decisional (criterion) bias, measurements were taken with the lens-magnified stimulus placed on the left and on the right. To control for size-color illusions, measurements were made with color filters in both arrangements before the eyes and under binocular vision (without color filters). RESULTS Free viewing resulted in a systematic underestimation of lens-induced aniseikonia that was absent with short presentations. Significant size-color illusions and decisional biases were found that would be mistaken for aniseikonia unless appropriate action is taken. CONCLUSIONS To improve their validity, aniseikonia tests should use short presentations and include control conditions to prevent contamination from decisional/response biases. If anaglyphs are used, presence of size-color illusions must be checked for. TRANSLATIONAL RELEVANCE We identified optimal conditions for administration of aniseikonia tests and appropriate action for differential diagnosis of aniseikonia in the presence of response biases or size-color illusions. Our study has clinical implications for aniseikonia management

A Recording and Analysis System of Bioptic Driving Behaviors

Millions of visually impaired people do not drive because they fail to meet the general vision requirements. There is a legal option in 38 US states where people with moderate central vision loss (e.g. visual acuity better than 20/200) may be permitted to drive while wearing spectacle-mounted bioptic telescopes. However, the safety of bioptic driving is still highly controversial, because bioptic use in driving is not well understood. Whether and how bioptic telescopes are actually used in driving, how they should be used appropriately, and whether their use results in better or worse driving performance has never been scientifically established. We are developing an in-car camera system that can be installed in bioptic drivers’ own vehicles to record their daily driving activities over long periods of time. Videos of the driver and traffic, GPS coordinates, XYZ acceleration, and vehicle black box data are recorded. We are also developing computer-aided reviewing techniques to automatically identify the most informative driving segments from the vast amount of data and, reconstruct the selected driving maneuvers on an interactive interface, so that these representative segments can be assessed off-line by driver evaluation and training specialists

Bitemporal hemianopia; its unique binocular complexities and a novel remedy

Abstract Bitemporal hemianopic visual field impairment frequently leads to binocular vision difficulties. Patients with bitemporal hemianopia with pre-existing exophoria complain of horizontal diplopia, sometimes combined with vertical deviation (with pre-existing hyperphoria). The symptoms are a result of the phoria decompensating into a tropia (hemi-slide) due to the lack of retinal correspondence between the remaining nasal fields of both eyes. We measured these effects using a dichoptic perimeter. We showed that aligning the eyes with prisms could prevent diplopia if the bitemporal hemianopia is incomplete. We also describe the successful use of a novel fusion aid -the 'stereo-typoscope' -that utilizes midline stereopsis to prevent diplopia resulting from hemi-sliding in patients with complete bitemporal hemianopia

Driving with Para-Central Visual Field Loss: Pilot Study

We studied how para-central visual field loss affects pedestrian detection in a driving simulator. Participants with para-central field loss had relatively good visual acuity (20/15 – 20/60) and 3 of 5 met local vision requirements for an unrestricted drivers license; however, they had lower detection rates and longer reaction times to pedestrians likely to appear within the blind area than in their seeing areas. They were at collision risk for 7% to 30% of pedestrians, whereas controls were at a collision risk for 0 to 4% of pedestrians

Aniseikonia Tests: The Role of Viewing Mode, Response Bias, and Size-Color Illusions

Citation: García-Pérez MA, Peli E. Aniseikonia tests: the role of viewing mode, response bias, and size-color illusions. Tran Vis Sci Tech. 2015;4(3): 9, doi:10.1167/tvst.4.3.9 Purpose: To identify the factors responsible for the poor validity of the most common aniseikonia tests, which involve size comparisons of red-green stimuli presented haploscopically. Methods: Aniseikonia was induced by afocal size lenses placed before one eye. Observers compared the sizes of semicircles presented haploscopically via color filters. The main factor under study was viewing mode (free viewing versus short presentations under central fixation). To eliminate response bias, a three-response format allowed observers to respond if the left, the right, or neither semicircle appeared larger than the other. To control decisional (criterion) bias, measurements were taken with the lens-magnified stimulus placed on the left and on the right. To control for size-color illusions, measurements were made with color filters in both arrangements before the eyes and under binocular vision (without color filters). Results: Free viewing resulted in a systematic underestimation of lens-induced aniseikonia that was absent with short presentations. Significant size-color illusions and decisional biases were found that would be mistaken for aniseikonia unless appropriate action is taken. Conclusions: To improve their validity, aniseikonia tests should use short presentations and include control conditions to prevent contamination from decisional/response biases. If anaglyphs are used, presence of size-color illusions must be checked for. Translational relevance: We identified optimal conditions for administration of aniseikonia tests and appropriate action for differential diagnosis of aniseikonia in the presence of response biases or size-color illusions. Our study has clinical implications for aniseikonia management

Video Test to Evaluate Detection Performance of Drivers with Hemianopia: Preliminary Results

The ability of individuals with hemianopia to compensate for their vision impairment by eye/head scanning to detect hazards in their non-seeing (blind) hemifield varies widely in both simulator and on-road tests. Conventional visual fields tests do not reflect this variability, while simulator and on-road tests are time-consuming and expensive. We therefore developed a simple, 15-minute video-based pedestrian detection test suitable for implementation on a desktop computer and monitor. The test was found to be sensitive to detection deficits in both hemianopia and quadranopia, and predictive of detection performance in a driving simulator. Our preliminary findings suggest that the test provides a simple method of measuring detection ability relevant to driving which may be useful both as a screening test and as an evaluation tool for rehabilitation devices and training

Simulator-Based Driving with Hemianopia: Detection Performance and Compensatory Behaviors on Approach to Intersections

OBJECTIVES In 22 states people with homonymous hemianopia (complete loss of the visual field on the sameside in both eyes) are explicitly prohibited from driving, as they do not meet the minimum visualfield requirements for driver licensing. However, there is little scientific evidence derived eitherfrom on-road or driving simulator studies about the safety of driving with hemianopia. If the eyeand head were kept stationary, people with hemianopia would not detect anything on the side ofthe field loss. In the real world, however, they may be able to compensate for the loss byexploring the affected (blind) side using head- and eye-scanning. It has been reported that inHolland (where driving with hemianopia is permitted), driving examiners consider increasedhead-scanning (especially on approach to intersections) to be an effective compensation forperipheral visual field defects (Coeckelbergh et al., 2002). Whether increased head-scanningwhile driving results in better detection performance has never been quantitatively investigated.We conducted a simulator-based evaluation of driving with hemianopia to investigate detectionperformance and head movement behaviors on approach to intersections.METHODSTo date, eight people with complete homonymous hemianopia (5 left and 3 right), and withoutvisual neglect or significant cognitive decline have completed the study. All had current or recentdriving experience (within the last 6 years). They completed two simulator sessions, one weekapart, driving in a high-fidelity simulator. Each session consisted of a familiarization period of30-60 minutes followed by 6 test drives (each about 12 minutes in duration). The primarysimulator task was to detect and respond (by a horn press) to the appearance of pedestrian targetsin a variety of traffic situations while driving according to the normal rules of the road. Targetsappeared randomly in locations relevant to real-world driving. There were two types of targets:“roadway” targets, which appeared either on the left or right of the road at small (~ 4°) or large(~14°) eccentricities from the presumed line of sight, and “intersection” targets, which wereplaced near or at intersections to test whether drivers were scanning effectively whenapproaching an intersection. Primary outcome measures were the percentage of targets detectedand reaction times when detected. Head movements were recorded with an inexpensive, lightweight,head-mounted optical head tracking system. Preliminary analyses of head movementbehaviors were conducted for intersections with stop or yield signs. Based on visual inspectionof the head movement plots, the number and direction of head movements were recorded and head movement scanning was graded on a 4-point scale (from 1 inadequate to 4 excellent). Inaddition, we are developing methods to automatically quantify driving skills (e.g., steering, laneposition) from the simulator data output.RESULTSDetection rates for roadway pedestrian targets were lower and reaction times longer on the blindside than the seeing side (p ≤ 0.05). Blind side: median detection rate 47% (IQR 22 to 63%),median reaction time 1.65s (IQR 1.05 to 1.84s); seeing side: median detection rate 93% (IQR89% to 99%), median reaction time 0.93s, (IQR 0.88 to 1.25s). Detection rates on the blind sidewere lower at the larger eccentricity (median 23%) than the smaller eccentricity (median 66%; p= 0.01). Drivers with right hemianopia (RH) detected 83% of intersection pedestrian targets onthe extreme left of an intersection but none on the extreme right, whereas drivers with lefthemianopia (LH) detected 33% on the extreme left and 80% on the extreme right. Better headscanningscores were associated with better detection rates for intersection targets at extremepositions on the blind side (Spearman r = 0.79, p = 0.02). Two of the drivers with LH showedinadequate scanning (grade 1), failing to scan to the left at more than 60% of intersections. Therest of the drivers with LH and all three with RH demonstrated better head-scanning (grades 2-4)with some compensatory head movement behaviors. At T-intersections with no incoming roadon one side, they scanned more frequently in the direction of the “absent” road when it was onthe blind side (RH 40% and LH 80%) than when it was on the seeing side (RH and LH \u3c10%).When there were incoming roads on both sides, the first head scan was normally to the left forLH, but it was to the right about 30% of the time for drivers with RH.CONCLUSIONSThese results provide evidence of widely varying levels of compensation and detection abilitiesamongst drivers with hemianopia, suggesting that fitness to drive should be evaluated on anindividual basis. The preliminary finding of a relationship between head-scanning score andintersection detection performance will be further evaluated using automated methods toquantify head movement behaviors and a larger sample of drivers with hemianopia. Furthermore,we will compare head movement behaviors of drivers with hemianopia to matched controldrivers without visual field loss.REFERENCESCoeckelbergh, T.R., Brouwer, W.H., Cornelissen, F.W., van Wolffelaar, P., Kooijman, A.C.(2002). The effect of visual field defects on driving performance: a driving simulator study. ArchOphthalmol, 120, 1509-1516

Assessing Driving Performance with Moderate Visual Field Loss

The minimum binocular horizontal field extent for driver licensingvaries widely between states in the USA. We examined the relationship betweenvisual field extent and open-road driving performance using a scoring method thatmeasured the quality of specific skills for a range of general driving maneuvers,as well as maneuvers that we expected to be difficult for people with restrictedfields. Twenty-eight current drivers with mild to moderate peripheral visual fieldrestrictions (123 ± 20°, V4e target) drove the 14-mile route. While most subjectswere scored as safe drivers, those with more restricted horizontal and verticalbinocular field extents showed significantly poorer skills in maneuvers for whicha wide field of vision is likely to be important (p ≤ 0.05): speed matching whenchanging lanes, and maintaining lane position and keeping to the path of the curvewhen driving around curves. Further studies using similar assessment methodswith drivers with more restricted fields are necessary to determine the minimumfield extent for safe driving

The Impact of Macular Disease on Pedestrian Detection: A Driving Simulator Evaluation

We describe the design of a driving simulator study to determine the effect of central visual field loss (due to macular disease) on pedestrian detection when driving. Pilot data suggest that a scotoma (blind area) in the central visual field can impair driving by increasing response time to hazardous circumstances