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and a documentation of  baby-blinding light levels in hospital nurseries

 

 

 
Footnotes:

 

47. KEY MM, HENSCHEL AF, BUTLER J, LIGO RN, TABERSHAW IR, EDE L. Occupational Diseases - A Guide to their Recognition. National Institute for Occupational Safety and Health, U.S. Government Printing Office, June 1977, page 496 top.

 

48. SLINEY DH, WOLBORSHT ML. Safety standards and measurement techniques for high intensity light sources. Vision Res 1980: 20: 1133-41 (see page 1137).

 

49. Y CAJAL SR. (first published in 1892 in "La Cellule", Paris), translated by THORPE SA, GLICKSTERN M. The Structure of the Retina. Springfield: Charles C. Thomas Publishers. 1972: pp. 93 and 153.

 

50. American Academy of Pediatrics and American College of Obstetricians and Gynecologists. Guidelines for Perinatal Care, 2nd edn. 1988: page 90 (top).

 


 


 

  

 

  

Preemies get more retinal irradiance

 

than safety guidelines allow for adults 

 
 

wpeB.jpg (11174 bytes)

Baby-blinding retinopathy of prematurity and intensive care nursery lighting
by H. Peter Aleff

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The wavelength region where the retina is most vulnerable to damage from light is the region from 435 to 440 nm. This wavelength region has caused much concern among specialists in Occupational Safety for adult industrial workers.

The 1974 Symposium on Illumination, sponsored by the U.S. National Institute of Occupational Safety and Health, NIOSH, warned that high lighting levels in that region of the spectrum could cause much damage to the eye, particularly retinal and macular degeneration (the macula is the most light-sensitive part of the retina).

Included in the Public Health Service's "Guide to the Recognition of Occupational Diseases" is this statement in the section on laser light:

"even a diffuse reflection from a high power laser can present an ocular hazard. An action spectrum has been recently developed to account for the variation in retinal sensitivity with wavelength for exposure times greater than ten seconds. The minimum threshold dose for retinal lesions occurs at 440 nm and is thought to be due to a photochemical process rather than to a thermal mechanism as in wavelengths greater than 500 nm" (47).

NIOSH's action spectrum or "blue-light hazard function" was published in 1980. It shows this maximum vulnerability range from 435 to 440 nm (48), as reproduced below in the second column of Table 1 for each of the wavelengths in column 1.

The third column gives the reciprocal of this hazard value, or the "retinal protection barrier" against that hazard. The last column indicates how much of the irradiance from the lamp in column 4 penetrates this barrier as the damage- weighted irradiance that harms the retina.
 

Table 1. Damage weighted irradiance from "Deluxe Cool White" fluorescent lamp

Transcriber's Note: This table has 5 columns: Wavelength in nanometers; Blue-light hazard function value; Reciprocal: blue light protection factor; Irradiance Watts per 10 nm as scaled; and Blue-light damage weighted irradiance. The point of this table is that the last column represents how much damage that frequency of light is causing. Look at the entry for 435 nanometers, you will see that the last column for that line is much larger than any other entry in the last column. This represents how dangerous this one spike of energy is in the fluorescent light.

 

 

Wave
length
in nm

Blue-
light
hazard

Reciprocal:
blue-light
protection

Total
irradiance
Watt / nm

Damage-
weighted
irradiance

315
355
365
375
385
395
400
405
410
415
420
425
430
435
440
445
450
455
460
465
470
475
480
485
490
495
500
505
515
525
535
545
555
565
575
585
595
600
605
615
625
635
645
655
665
675
685
695
700

--
--
--
--
--
--
0.10
0.20
0.40
0.80
0.90
0.95
0.98
1.00
1.00
0.97
0.94
0.90
0.80
0.70
0.62
0.55
0.45
0.40
0.22
0.16
0.10
 
 
 
 
 
 
 
 
 
 
0.01
 
 
 
 
 
 
 
 
 
 
0.001

--
--
--
--
--
--
10
5
2.5
1.25
1.11
1.05
1.02
1.00
1.00
1.03
1.06
1.11
1.25
1.43
1.61
1.82
2.22
2.50
4.54
6.25
10.0
 
 
 
 
 
 
 
 
 
 
100
 
 
 
 
 
 
 
 
 
 
 1000

0.122
0.122
0.955
0.321
0.416
0.581
--
2.432
 
0.959
 
1.137
 
6.120
 
1.338
 
1.440
 
1.527
 
1.650
 
1.727
 
1.839
 
1.935
1.990
2.118
2.233
4.307
2.476
2.598
3.179
2.905
2.991
 
3.073
3.029
2.952
2.808
2.664
2.355
2.074
1.548
1.021
0.188

--
--
--
--
--
--
--
0.4864
 
0.7672
 
1.0802
 
6.1200
 
1.2979
 
1.2960
 
1.0689
 
0.9075
 
0.6908
 
0.2942
 
0.2419
0.0995
0.0678
0.0447
0.0560
0.0198
0.0130
0.0095
0.0058
0.0030
 
0.0031
0.0030
0.0030
0.0028
0.0027
0.0024
0.0021
0.0015
0.0010
0.0002

Total irradiance
Damage weighted as % of full

71.1W
100%

14.6W
20.51%

 

Bluelightbarrier.jpg (28061 bytes)

Figure 2 illustrates how the most intense emission spike from the fluorescent lamp above passes right through the broad breach in the retinal 

protection barrier -- the "retinal vulnerability window".  The caption reads:  "Irradiance from "Deluxe Cool White" fluorescent lamp, retinal protection barrier, and damage- weighted irradiance through the "vulnerability window" in that barrier."
 
Transcriber's Note: Complex graph show 3 overlapping graphs (all 5 use light wavelength as the horizontal axis): first the lamp irradiance, the second shows the retinal protection barrier, the third shows damage-weighted irradiance. This final graph shows a single high peak around the violet light.

The NIOSH data for this table and graph derive mostly from experiments which destroyed the retinae of monkeys, pigs, rats, and a variety of other mammals. The retinal structure of all mammals is virtually the same (49). Clinical experience with victims of welding accidents and accidental exposures to excess laser light confirms that humans are just as vulnerable in the same wavelength region as test animals. There is, thus, no basis for assuming that the developing preemie retina during its period of greatest vulnerability is immune to irradiation in a wavelength which quickly burns the retinae of other mammals. Much of the nursery lamps' energy is concentrated in precisely the wavelength that is known to cause the most damage to the retina.

Yet, the American Academy of Pediatrics prescribes for unprotected preemies weeks and months of continuous irradiation with lamps of extra high output in that most damaging wavelength, and at an intensity which is far in excess of adult tolerance levels. Its Committee on Fetus and Newborn specified in its 1977 Standards and Recommendations for Hospital Care of Newborn Infants that all infant care areas should have 100 foot-candles (ftc) of illumination from "Deluxe Cool White" fluorescent tubes (44). In October 1988 it reduced this intensity to 60 ftc (50).
 
As I will show in the next section, 60 ftc intensive care nursery lightning will expose a preemie's retinae in 15 min or less to the dose of retinal irradiance which NIOSH has established as the occupational danger limit for healthy adult industrial workers.
 

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