Driving is a complex task, which needs, among others, a good contrast perception of objects in movement in varying light conditions. Drivers received most of the information by means of his eyes. The area of the space perceived by the eye when a point of fixation is observed is defined as the visual field and can be affected by such factors as the design of the vehicle, the ambient conditions, the traffic, the speed of traffic and the physical and psycophysical conditions of the driver. So, it must be considered the importance that a suitable visual field has for a safe driving.

Light sensitivity or its inverse -the luminous differential threshold to the detection of a stimulus- changes along the field of vision. Visual fields are explored in order to locate injuries along the optical pathway. Visual field extent depends on the number and on the functioning of the receptive fields of the ganglionar cells. A technology used habitually to measure it is the automated perimetry1. The frequency-doubling technology (FDT) allows the measurement of contrast perception variation by generating a frequency doubled illusion, which is registered by a set of cells in the Magnocelular way, specifically by the subgroup named cells My, that are the managers of the processing of the form and of the movement. They are the 15-25% of the whole of neurons. Any injury suffered by these cells provokes a visual periferic field decrease, which will be detected by the FDT2.

The aim of this study is to check the contrast perception variations in usual drivers concerning objects in movement, in different luminance conditions, by using the FDT. Nowadays, the FDT is the only way to know the functionality of the Magnocellular System. It allows to know the contrast threshold in different areas of the retina and fovea. Therefore, it is the suitable method for the study of a complex task as driving.

Methods

Conclusions References

Results

FIGURE 1: Humphrey frequency doubling perimetry (FDT, Zeiss)

1. Bisdorff, A. R., Wolsley, C. J., Anastasopoulos, D., Bronstein, A. M., and Gresty, M. A. The Perception of body verticality (subjective postural vertical) in peripheral and central vestibular disorders. Oxford Journals 119:1523-1534, 1996.2. Carrasco-Font, C., Lorenzo-Martínez. S., Gili-Manzanero, P., Arias-Puente, A., Andrés-Alba Y., Matilla-Rodríguez, A., Ortigueira, J.A. Influencia de la función visual de vida de los pacientes con glaucoma. Arch Soc Esp Oftalmol 83:249-256, 2008.3. Fernández, Dr. R. A., Grenón Dr. F. C., Lazaroff, Dr. J. S., Lazaroff, P. E. Tratamiento médico inicial del glaucoma primario agudo: revisión bibliográfica. Revista de Posgrado de la VIa Cátedra de Medicina. Num. 144 – Abril 2005.l4. Guerraz, M., Yardley, L., Bertholon, L., Pollack, L., Rudge, P., Gresty, M. A. and Bronstein, A. M. Visual vertigo: symptom assessment, spatial orientation and postural control. Brain 124:1646-1656, 2008.5. Bisdorff, A. R., Wolsley, C. J., Anastasopoulos, D., Bronstein, A. M., and Gresty, M. A. The Perception of body verticality (subjective postural vertical) in peripheral and central vestibular disorders. Oxford Journals 119:1523-1534, 1996.6. Anderson, D. R. Automated Static Perimetry. Mosby Year Book. 1992.7. Choplin, N. T., Edwards, R. P. Visual Field Testing with Humphrey Field Analyzer. Slack Incorporated. 1999.

In conclusion, there is a significant decrease in the contrast threshold of objects in movement, when there is a drop into the illumination of the driver visual system. The value decreases in a significant way from 50 %. To relate ocular movements strategy for the fixation to the threshold of mesopic contrast of stimuli in movement in the whole field of vision, is going to allow to give practical and concrete solutions in the design and regulation of some elements of the interior of the vehicle and the exterior lighting.

Professionals of the vision and drivers have to know that, every time in a more undoubted way, the use of visual criteria in visual safety must be used for the drivers' detection strategy of the ocular motility and threshold of contrast of the field of vision. This must be applied to reduce the risk in the night driving of vehicles, area on which preventive and educational campaign should be done.

Different luminance levels have been established by using neutral optical filters, defined by their absorption (A) and their optical density (DO): [FA 20%/0.2; FB 50%/0.5; FC 74%/0.74; FD 80%/0.8]. Relationship between the optical density and the filter Transmittance is: DO=log (1/T). Also, test luminance through the filter is calculated by L=L0.T, where L0 is the luminance value without filter. Finally, the luminance can be also calculated by L=L0/10.DO, knowing that DO=log (1/T).

The visual field of 11 vehicle drivers (17-85 years) was check with a frequency-doubling technology (FDT) campimetry. The device uses a sinusoidal grid with low spatial frequency (0,25 cycles/º), which blinks rapidly, with a 25Hz phase variation, produces into the subject the feeling that the grid has the double of spatial frequency (double illusion).

FIGURE 2: Illusion of the duplication of the frequency

LLIGHTING INFLUENCE IN THE PERCEPTION OF IGHTING INFLUENCE IN THE PERCEPTION OF THE CONTRAST OF OBJECTS IN MOVEMENT THE CONTRAST OF OBJECTS IN MOVEMENT

BY USING FREQUENCY DOUBLING TECHNOLOGY (FDT)BY USING FREQUENCY DOUBLING TECHNOLOGY (FDT)GÓMEZ-TORTUERO E1, SÁNCHEZ-RAMOS C1, VINAS-PENA M1, BONNIN-ARIAS C1, GALLEGO COLLADO B2.

1Neurocomputing and Neurorobotics Group, 2Ophthalmology and Othorhinolaryngology Departments Universidad Complutense Madrid.UNIVERSIDAD COMPLUTENSE OF MADRID, MADRID (SPAIN)

ISAL 2009 – 8th International Symposium on Automotive Lighting . Darmstadt (Germany) . SEPTEMBER 2009.

egomezto@opt.ucm.esIntroduction

FDT devices operates in a simple way and its methodology has several advantages in comparison to other older perimeters: • The FDT can use in the sifted one in way supra-threshold or of complete threshold• Threshold exams can be checked in 1-5 min only.• The range of contrast is 56-0 dB.• The stimulus comprises 17 FD patterns (double frequency sinusoidal grating) plus patterns of intent of capture and fixation.• The stimulus is black/white and has a background illumination of 100cd/m2.• Patches are not needed for the eye without examining, it automatically covers6,7.

FIGURE 3: Scheme where are represented the different zones of the visual field

To obtain the conditions of mesopic lighting that needs has been used the exposure meter IL1400*3448, calibrated to measure levels of lighting in cd/m2 in combination with a detector SPLO25Y*238. Four types of grey filters by Essilor with different absorbances have been used: filter A (FA) with 20 %, filter B (FB) with 50 %, filter C (FC) with 70 % and filter D (FD) 85 %. Also threshold values have been checked without filter (SF).

Q1 Q2

Q3 Q4

1

FIGURE 4: Scheme where are represented the different quadrants of the visual field

Foveal zone

Q1 (quadrant 1)

Q2(quadrant 2)

Q3(quadrant 3)

Q4 (quadrant 4)

1 2+3+6+7 4+5+8+9 10+11+14+15 12+13+16+17

DESVIATIONS OF THE CONTRAST THRESHOLDS

IN THE FOVEAL ZONE OF THE VISUAL FIELD

26,62

25,75

30

28,12

29,37

23

24

25

26

27

28

29

30

31

SF FA* FB* FC* FD*

SF

FA*

FB*

FC*

FD*

FIGURE 5: Means and standard deviations in dB of the contrast thresholds determined in the foveal of visual field

DESVIATIONS OF THE CONTRAST THRESHOLDS IN THE FOVEAL ZONE AND QUADRANTS OF VISUAL FIELD

0

5

10

15

20

25

30

35

1 Q1 Q2 Q3 Q4

SF FA FB FC FD 1 Q1 Q2 Q3 Q4

SF 29.45 ± 4.4 28.79 ± 3.9 27.59 ± 3.6 29.50 ± 4.0 28.65 ± 4

FA 27.72 ± 6.2 26.0 ± 3.9 24.95 ± 4.6 27.84 ± 3.3 27.09 ± 3.3

FB 28.27 ± 5.2 26.25 ± 3.9 24.7 ± 3.5 28.06 ± 4.3 26.52 ± 3.7

FC 24.9 ± 5.9 23.81 ± 5.4 22.9 ± 5.6 24.43 ± 6.3 24.13 ± 5.9

FD 23.09 ± 9.5 21.25 ± 8.38 19.56 ± 8.9 21.65 ± 9.1 21.20 ± 9.1

Results obtained without filter were [NF: 2.52±2.4 – 6.35±6.0 (dB), p=0.000]. Significant decreases in contrast threshold were obtained when optical filters with absorption greater than 74% (C and D) were used: [2.70±2.7 – 4.05±3.7] (dB), p=0.000]. In the fovea, a decrease of 5dB (10-15% lost), was obtained [NF: 30,00±4,59; FA: 28,12±5,39;FB: 29,37±4,34; FC: 26,62±4,27; FD: 25,75±8,90].

FIGURE 6: Means and standard deviations in dB of the contrast thresholds determined in the foveal zone and quadrants of visual field.

TABLE 2: Means and standard deviations in dB of the contrast thresholds determined in the foveal and quadrants of visual field

zone SF FA* FB* FC* FD*

1 (fovea) 30,00±4,59 28,12±5,39 29,37±4,34 26,62±4,27 25,75±8,90

TABLE 1: Means and standard deviations in dB of the contrast thresholds determined in the foveal and paracentral zones of visual field