Infrared Cataract And Temperature Elevation Within The Eye ... · ICNIRP 8th INTERNATIONAL NIR WORKSHOP Cape Town, South Africa, 9-11 May 2016 Infrared Cataract And Temperature Elevation

ICNIRP 8th INTERNATIONAL NIR WORKSHOP

Cape Town, South Africa, 9-11 May 2016

Infrared Cataract And Temperature Elevation Within The Eye

Tsutomu OKUNO

International Commission on Non-Ionizing Radiation ProtectionNational Institute of Occupational Safety and Health, Japan

13.05.2016 Tsutomu OKUNO



What is infrared cataract?

IR cataract occurs in workers who have been engaged in the glass or steel industry for many years (e.g. glassblower's cataract).

IR cataract is associated with exposure to intense IR emitted from molten materials and the inside of industrial furnaces.

Recently, there is concern that infrared LEDs and diode lasers may cause cataract.



Interaction mechanism Photochemical mechanism

Thermal mechanism

Chemical reactionIR

photon

Temperature elevation

Chemical reactionIR

energyCataract

Cataract



Temperature elevation within the eye

Tsutomu Okuno (1991) Thermal effect of infra-red radiation on the eye: a study based on a model, Ann. Occup. Hyg. 35, 1-12.

Tsutomu Okuno (1994) Thermal effect of visible and infra-red radiation (i.r.-A, i.r.-B and i.r.-C) on the eye: A study of infra-red cataract based on a model, Ann. Occup. Hyg. 38, 351-359.

Calculation based on a model of IR absorption and heat transfer within the eye



Assumptions about IR absorption (1)

IR Optic axis

absorption coefficient



Assumptions about IR absorption (2) Monochromatic radiation

Black-body radiation

Visible: 400 nm, 425 nm, … , 775 nmIR-A: 800 nm, 825 nm, … , 1400 nmIR-B: 1425 nm, 1450 nm, … , 1900 nm

1200°C: Working temperature of glass 1500°C: Melting point of iron Time

Irrad

ianc

e

0



Assumptions about heat transfer

Inside:heat conduction

Choroid:constant

temperature

Cornea:heat flux

The relative temperature elevations above normal, unexposed conditions within the eye were calculated.



0

1

2

3

4

5

6

0 2 4 6 8 10

Tem

pera

ure

elev

atio

n (°

C)

Time (min)

Time course of temperature elevation

0

1

2

3

0 2 4 6 8 10

Tem

pera

ure

elev

atio

n (°

C)

Time (min)Anterior surface of corneaAnterior surface of lensPosterior surface of lens

λ = 600 nm λ = 1700 nm

(100 mW/cm2)



Distribution of temperature elevation (1)VisibleIR-A

1000 nm100 mW/cm2

10 min



Distribution of temperature elevation (2)IR-BIR-C

1500 nm100 mW/cm2

10 min

Black-body radiation of

1200°C, 1500°C



0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500

Tran

smitt

ance

Wavelength (nm)

CorneaAqueousCornea and aqueous

Transmittance of cornea and aqueous humor→ IR-B, IR-CVisible, IR-A ←

CIE 203 :2012. A Computerized Approach to Transmission and Absorption Characteristics of the Human Eye



Spectral distribution of black-body radiation→ IR-B, IR-CVisible, IR-A ←

0E+00

2E+10

4E+10

6E+10

8E+10

0 1000 2000 3000 4000 5000Spec

tral

radi

ance

(W/m

3 sr)

Wavelength (nm)

1500°C1200°C

92%

84%



Mechanisms of temperature elevation

Goldmann

Vogt

Okuno

Radiation

Heat conduction

Visible, IR-A

IR-A, IR-B



Maximum temperature elevation in the lens

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

400 600 800 1000 1200 1400 1600 1800 2000

Tem

pera

ture

ele

vatio

n (°

C)

Wavelength (nm)

Visible IR-A IR-B

100 mW/cm2

10 min



Summary on temperature elevation (1) The temperatures within the eye increase steeply

with exposure for about 2 min, then level off and remain constant for exposures for more than about 5 min.

For exposure to visible radiation and IR-A, the temperature elevation within the eye is the greatest at the iris.

For exposure to IR-B and IR-C, the temperature elevation within the eye is the greatest at the center of the anterior surface of the cornea.



Summary on temperature elevation (2) For exposure to black-body radiation of 1200°C and

1500°C, the temperature elevation within the eye is the greatest at the center of the anterior surface of the cornea.

Visible radiation and IR-B induce greater temperature elevations in the lens than IR-A, and are supposed to be more effective in causing cataract.



Summary on mechanisms For exposure to visible radiation and IR-A, the

radiant energy is absorbed and converted into heat in the iris, which is then conducted to the lens.

For exposure to IR-B and IR-C, the radiant energy is absorbed and converted into heat in the cornea, which is then conducted to the lens.

For exposure to black-body radiation of 1200°C and 1500°C, the radiant energy is absorbed and converted into heat in the cornea, which is then conducted to the lens.



Cataract formation in rabbits exposed to IR-A

Tsutomu OKUNO 1, Masami KOJIMA 2,Yoko YAMASHIRO 2, Sachiko YAMAGUCHI-SEKINO 1,

Yoshihisa ISHIBA 3, David H. SLINEY 4

1 National Institute of Occupational Safety and Health, Japan2 Kanazawa Medical University3 Yamamoto Kogaku, Co., Ltd.4 Johns Hopkins University Bloomberg School of Public Health



Exposure to 808 nm IR-A



Results

After one day of exposure at 6.1 W/cm2 for 4 s



Threshold irradiance vs. exposure duration

0.00.51.01.52.02.53.03.54.04.5

0 100 200 300 400

Ther

shol

d irr

adia

nce

(W/c

m2 )

Exposure duration (s)



CIE technical report on infrared cataract

Okuno, T. (Chair) JapanKojima, M. JapanSchulmeister, K. AustriaShang, Y.-M. Chinese TaipeiSliney, D. USASöderberg, P. SwedenStuck, B. USASuzuki, Y. JapanTengroth, B. Sweden

Documents

Infrared Cataract And Temperature Elevation Within The Eye ... · ICNIRP 8th INTERNATIONAL NIR WORKSHOP Cape Town, South Africa, 9-11 May 2016 Infrared Cataract And Temperature Elevation