ORIGINAL ARTICLE
Year : 1984 | Volume
: 32 | Issue : 5 | Page : 351--353
Blue light hazard and sunglass phototransmission
S Amrik Pabley, J Francis Sousa, C Eugene Moss
Department of Ophthalmology. University of California, Davi. California, USA
Correspondence Address:
S Amrik Pabley
Department of Ophthalmology, University of California, Davis, California
USA
How to cite this article:
Pabley S A, Sousa J F, Moss C E. Blue light hazard and sunglass phototransmission.Indian J Ophthalmol 1984;32:351-353
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How to cite this URL:
Pabley S A, Sousa J F, Moss C E. Blue light hazard and sunglass phototransmission. Indian J Ophthalmol [serial online] 1984 [cited 2021 Sep 19 ];32:351-353
Available from: https://www.ijo.in/text.asp?1984/32/5/351/27509 |
Full Text
Because of the photochemical toxic effects of blue light on the retina of experimental animals,[1],[2],[3] it is natural to extend the concern to humans.[4] subThis may be important in aphakic eyes as evidenced from the work of S. Lerman5sub shown in [Figure 1]. This figure represents transmission characteristics of normal human crystalline lens from 6 months to 82 years of age. X-axis is the wavelength in nanometers and Y-axis is the percent transmission of light. The human lens provides excellent near ultraviolet and blue light filtration from age 25 onwards. Post-cataract surgery this natural protection is lost and may need to be artificially replaced. Different sunglasses give different protection and there are currently no standards by which to guide ophthalmologists in, advising their patients.
In an attempt to discern how well commercially available sunglasses protect us from blue light, we performed this study.
MATERIALS AND METHODS
Foster Grant is the major United States manufacturer of commercial sunglasses. We used their sunglasses in our study. Approximately 90 percent of the sunglasses sold have plastic lenses, so we limited out study to plastic lenses. We studied seven solid tints and three gradient tints. Gradient tints gave nonreproducible results for phototransmission and were excludea from our results.
The Perkin-Elmer model 330 spectrophotometer was used to measure transmission of these glasses. This model has a measuring wavelength range of 187 to 2,500nm
OBSERVATIONS
A typical spectral transmission curve is shown in [Figure 2]. The X-axis is the wavelength in nanometers and the Y-axis is the percent transmission of light. Blue light transmission is shown with hatch marks. Here, the specimen 4 Gray FG 9110 shows the maximum blue light transmission 19%, maximum visible transmission 37% and the ultraviolet cutoff at approximately 390 rim. Hence, this lens will protect against ultraviolet radiation below 390 nm and will admit a maximum of 19% of the blue light.
Our results are shown in [Table 1]. All of these Foster Grant sunglasses have low blue light transmission, ranging from 9 to 31%. Brown tinted plastic lenses appear to provide better protection from the blue light than do gray or green plastic lenses. The brown lenses also allow good visible light transmission while providing selective blue light protection. Therefore, blue to visible light transmission ratios are lower than those for either the green or gray lenses. We also found that all of these Foster Grant glasses have very good ultraviolet filtration.
DISCUSSION
The blue light hazard refers to the retina's susceptibility to damage from shorter wavelength visible light. This hazard is thought to be significant when the spectrum of an optical source contains a large proportion of blue light. Electromagnetic spectrum includes ultraviolet, visible and infrared radiations. Visible light is generally considered to be from 400 to 700 nanometers. The blue light hazard considered here is primarily concerned with the wavelength between 400nm to 500 nm.
Light energy produces damage to the eye in three ways, photomechanical, thermal and photochemical. Photochemical damage is less well understood. Photomechanical and thermal damage generally tend to be caused by high-intensity, short duration light sources, and is relatively independent of wavelength, but the photochemical damage on the other hand is caused by low-intensity and relatively long duration light exposure and appears to be highly dependent on the wavelength of light.
There have been a few landmark studies in the definition and understanding of photochemical retinal damage and the blue light hazard. In 1973, Theodore Lawwill at the University of Louisville, studied the effects of long exposure low-intensity light on the rabbit retina. However, the blue light hazard was not generally accepted until 1979 when the elegant work of William Ham[2] and associates at the Medical College of Virginia defined the histopathology of the photochemical lesion induced by low-intensity blue light. Their work with rhesus monkeys demonstrated that the photochemical lesion is strongly dependent upon wavelength, such that retinal sensitivity to injury increases sharply at the blue end of the visible spectrum. In 1980, Harold Sperling 3 showed selective damage to rhesus, monkey cones with intermittent blue light exposure which he called blue blindness. This photoreceptor damage with intermittent blue light exposure differs from Ham's findings of pigment epithelial damage with continuous blue light exposure. More recently Calkins 4 has studied light exposure to human retina from various ophthalmic instruments. These instruments emit a significant proportion of their light energy in the blue spectrum and he has suggested that they may be potentially harmful to human retina. Histopathology of the photochemical lesion has been studied at the light microscopic and at the electron microscopic levels in animal.models. Acutely, we see the damage to the retinal pigment epithelium characterized by inflammatory reaction, clumping of melanosomes, machrophage invasion and melanin photocytosis. This is followed by photoreceptor degeneration 2-5 days later. The specific photochemical reactions responsible for this type of injury are not known at the present time.
As the significance of the blue light hazard and photochemical damage becomes better understood, ocular protection may become necessary. Out limited study shows the brown, plastic lenses provide better protection from blue light than gray or green plastic lenses.[5]
References
| 1 | Lawwill T., 1973. Invest. Ophthalmol. vis. sci. 12:4551 |
| 2 | Ham W.T., Mueller HA, Rubbolo H.H. and Clark A.M., 1979. Photochem. Photobiol. 29: 735 |
| 3 | Sperling H.G.,Johnson C. and Harwerth KS., 1980. Vision Research. 20: 1117 |
| 4 | Calkins J.L. and Hochheimer B.F., 1980. Invest. Ophthalmol. Visual Sci. 19: 1009 |
| 5 | Lerman S., 1980. Radiant energy and the eye. New York, MacMillan. p 88 |
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