masashiro shibuya, junichi hirota, kimihiro yamanaka and mitsuyuki kawakami tokyo metropolitan...

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Examination of the causes of visual ability lowering due to aging Masashiro SHIBUYA, Junichi HIROTA, Kimihiro YAMANAKA and Mitsuyuki KAWAKAMI Tokyo Metropolitan University 1

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Examination of the causes of visual ability lowering due to

aging

Masashiro SHIBUYA, Junichi HIROTA, Kimihiro YAMANAKA and Mitsuyuki KAWAKAMI

Tokyo Metropolitan University

1

Japan Now!

Age groups Both sexes Male Female 0~14 years old 1718 13.5 880 14.1 838 12.8

15~64 years old 8234 64.5 4142 66.5 4092 62.5

65 years and over 2819 22.1 1203 19.3 1616 24.7

70 years and over 2017 15.8 820 13.2 1197 18.3

75 years and over 1321 10.3 498 8.0 823 12.6

80 years and over 751 5.9 251 4.0 500 7.6

Total 12771 100.0 6225 100.0 6546 100.0

Population Estimates by Age Group and Sex

Percentage distributionPopulation (Ten thousand persons)Sept. 15,2008 (Provisional estimates)

2

Employee by age group and type of employment

    Employee

Employee,

excluding

excecutive of company or

corporation

Regular staff

Non-regular

staff

Part-time

worker, Arbeit(tempo

rary worker

)

Part-time

worker

Arbeit (tempo

rary worker

)

Dispatched

worker from

temporary

labour agency

Contract

employee or entrust

ed emplo

yee

Other

Feb. 1988 4422 4132 3377 755 599 443 156 - 156  15 to 24 years old 620 617 512 106 96 17 79 - 10  25 to 34 years old 1005 983 878 105 84 59 25 - 21  35 to 44 years old 1220 1149 927 222 198 177 21 - 24  45 to 54 years old 977 889 717 172 143 130 13 - 29  55 to 64 years old 494 422 307 115 61 48 13 - 54  65 years old or more 106 71 36 34 16 11 5 - 18Feb. 1997 5349 4963 3812 1152 945 638 307 - 207  15 to 24 years old 728 725 491 234 220 28 192 - 14  25 to 34 years old 1249 1219 1049 169 132 89 43 - 37  35 to 44 years old 1119 1052 832 220 194 173 21 - 26  45 to 54 years old 1315 1195 929 266 235 213 22 - 31  55 to 64 years old 740 633 448 185 123 106 17 - 62  65 years old or more 199 139 63 76 41 29 12 - 352007 Yearly average 5561 5174 3441 1732 1164 822 342 133 298 137  15 to 24 years old 545 544 292 253 202 31 171 18 25 8  25 to 34 years old 1289 1265 940 326 181 116 64 52 67 26  35 to 44 years old 1288 1222 890 332 229 199 30 31 48 24  45 to 54 years old 1155 1068 740 327 240 218 22 15 45 27  55 to 64 years old 997 866 512 354 230 197 33 11 81 32  65 years old or more 287 209 68 140 83 61 22 5 32 20

(Ten thousand persons)

Government policy Employment Services for the Elderly

Subsidies for Promoting the Employment of the Elderly

Support for Employers involved in the Employment of the Elderly

Educational Activities Concerning Employment of the Elderly

Supporting the Vocational Goals of Middle-aged and Older Workers

4

aim

To make guidelines for job redesign by clarifying the cause of older people's visual ability lowering.

More than 80% of daily living information comes through the eyes

5

Scenery of experiment

Landolt ring

6

The condition of this experiment

1 2 3 4 5 6 7

Angle(o) 13.7o 11.7o 9.7o 7.7o 5.7o 3.7o 1.7o

Distance(cm)

13.08 15.39 18.63 23.53 31.81 48.81 105.05

21 kinds of combinations

the visual index presentation distance

1 2 3 4 5 6 7

Small 0.46 0.54 0.65 0.82 1.11 1.71 3.67

Medium 0.69 0.81 0.98 1.23 1.67 2.56 5.50

Large 0.91 1.07 1.30 1.64 2.22 3.41 7.34

the index size of the experiment conditions

7

The procedure of the experiment

Accommodo PolyrecorderThe subjective symptoms index (SSI)

Watch the marker until a Landolt ring appeared

Shift visual lines to the ring

Tell aloud its break as soon as possible

Return his visual lines to the marker after the ring disappeared

Taking a picture of pupil

Accommodo PolyrecorderThe subjective symptoms index (SSI)

8

The evaluation indexes(1) Reaction time

The time the subject took from the moment he saw the Landolt ring to the moment he told the break of the ring.

(2) The direction of the visual lines The reflection of the maker or the Landolt ring on the

subject’s eyes was used. The light from the marker or ring was reflected on the pupil. The positional relation between this reflection light(Purkinje-Sanson mirror image) and the pupil was used as a visual Line index.

(3) The degree of eye strain This was examined using the relative evaluation before

and after work of Near Point Distance, Contraction Time and Relaxation Time obtained from the Accommodo Polyrecorder, and Subjective Symptoms Index.

9

Result and discussion

(1) Reaction Time

Variables Observed variance of ratio p-value

individual differences(A) 89.869 4.07E-73 **

visual index sizes(B) 2.338 0.098093

visual index distances(C) 11.302 1.66E-11 **

factor(AB) 1.626 0.070586

factor(AC) 1.358 0.075913

factor(BC) 1.449 0.142286

factor(ABC) 0.928 0.653934

The results of the ANOVA (younger person)

**: p<0.01

10

Result and discussion

(1) Reaction Time

The results of the ANOVA (older person)

**: p<0.01

Variables Observed variance of ratio p-value

individual differences(A) 70.640 9.36E-38 **

visual index sizes(B) 44.785 6.5E-17 **

visual index distances(C) 34.510 8.03E-29 **

factor(AB) 1.348 0.221566

factor(AC) 2.117 0.002662 **

factor(BC) 5.827 1.09E-08 **

factor(ABC) 2.333 2.11E-05 **

Average reaction time by size S

young old0.000

0.500

1.000

1.500

SML

rea

cti

on

tim

e(s

ec)

**

**

**: p<0.01

12

Multiple comparison by visual line shift distance

distance 1 2 3 4 5 6 7 distance 1 2 3 4 5 6 71 ** ** ** ** ** 1 ** ** ** ** **2 * * * ** 2 * ** ** ** **3 3 * *4 45 56 67 7

Young person old person

*: p<0.05,**: p<0.01

13

Reaction time in Size S

1 2 3 4 5 6 70

0.5

1

1.5

youngold

visual line shift distance

reac

tion

tim

e(se

c)

14

(2) The visual lines

1 2 3 4 5 6 7-10.00

-5.00

0.00

5.00

10.00

young(right eye)young(left eye)old(right eye)old(left eye)

Visual line distance (o)

Vis

ual l

ine

slip

page

(pix

)

The regression lines of visual lines

15

summary The insufficient eye ball adduction of

older persons causes more significant distance influence on reaction time in Size S compared with younger persons.

Specially in the distances of 11.7 o and 13.7o, information fusion from the right and the left eyes is much more difficult, which is thought to make great difference in reaction time.

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(3) The degree of eye strain

Near Point Distance Contraction Time Relaxation Time0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

Young peopleOld people

Th

e r

ela

tive

va

lue

s o

f e

fore

an

d a

fte

r w

ork

(%)

17

The items of the subjective symptoms index

Category ⅠFeelings of drowsiness

Category ⅡFeelings of uneasiness

Category ⅢFeelings of discomfort

Category ⅣFeelings of

languor

Category ⅤFuzzy feelings

Feel drowsy Feel uneasy Have a headache

My arms feel heavy

Have blear eyes

Want to lie down Feel depressed Feel heavy in the head

My lower back feels heavy

Have eyestrain

Yawn Feel nervous Feel sick My hands or fingers ache

Have sore eyes

Can't motivate myself

Feel irritated Feel my brains muddled

My legs feel feel heavy

My eyes are blurred

Feel tired all over

Can't think clearly

Feel dizzy Have stiff shoulders

 

Japan Society for Occupation Health

18

The avarage value of the fifth category before and after work

before work after work0.000

0.500

1.000

1.500

2.000

2.500

Young personOld person

sco

re o

f ca

teg

ory

V

19

Conclusion The cause of longer time of visual

recognition because of aging is the lowering of the visual focusing ability.

The eyeball adduction of older people is insufficient at a short distance compared with that of younger people.

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