The Effect of Blue Light on AMD after Cataract Surgery
Controversies about cataract surgery and the contribution of blue light to AMD
There is controversy regarding whether people who have had cataracts removed surgically and artificial lenses implanted have an increased susceptibility to AMD. The controversy is fed by contradictory studies promoted by manufacturers of artificial lenses. The discussion revolves around whether the normal yellowing of the natural lens, which can block up to 80% of incident blue light from reaching the retina, is protective of AMD and that the implanted lens should therefore block blue light to provide the same protection from blue light as a normal aged lens. Some lens manufacturers argue that the evidence for this is weak and studies indicate that the incidence of AMD of people who have clear lenses implanted is quite low, and no higher than those with tinted, blue blocking artificial lenses.
Manufacturers of yellow tinted blue blocking lenses argued that this argument appeared to be resolved by a study in Ophthalmology in 2012 claiming;
These data strongly support the past findings of an association of cataract surgery with late AMD ...and suggest the importance of considering these findings when counseling patients regarding cataract surgery.1
However, another study later that year in the same journal was unable to demonstrate a benefit within 3 years of cataract surgery.2
Some studies supported the premise that increased exposure to blue light that results from cataract surgery contributes to the development of AMD. The authors of the paper Prevention of Increased Abnormal Fundus Autofluorescence with Blue Light-Filtering Intraocular Lenses. J Cataract Refract Surg. 2015 Oct 12.3 concluded that their study demonstrated that after 2 years
"The incidence of AMD was lower in eyes with a yellow-tinted [blue-light blocking] IOL.
The controversy originated primarily from the publication of a paper in JAMA Ophthalmology in 2009 which concluded
The low incidence rate of neovascular AMD development between 1 week and 1 year after cataract surgery did not support the hypothesis that cataract surgery increases the risk of AMD progression4.
Some researchers who had previously claimed that blue light exposure does not contribute to the development of of AMD seized on the JAMA Ophthalmology paper to support their proposition. However, the results and implications of this study were controversial from the outset, as expressed in an editorial published in that same issue Is the Risk of Incidence or Progression of Age-Related Macular Degeneration Increased After Cataract Surgery?5
Additionally, many earlier studies, such as the paper Age-Related Maculopathy and the Impact of Blue Light Hazard, by Algarve et al. found increased progression of AMD after cataract surgery6. Some subsequent studies, including Ocular Risk Factors for Age-Related Macular Degeneration also determined that cataract surgery increases susceptibility to AMD from blue light exposure. These authors concluded
Cross-sectional associations of ocular factors such as cataract, cataract surgery, and refractive errors with early AMD lesions found in Latinos are consistent with those in non-Hispanic Whites. Additionally, prior cataract surgery was associated with advanced AMD.7
This subject was discussed at the 1st World Congress on Controversies in Ophthalmology (COPHy) in Prague, Czech Republic March 4-7, 2010. A. Pollack, of the Kaplan Medical Center at the Hebrew University in Israel, presented data from 6 studies they performed which concluded
These studies describe an acceleration of the course of dry AMD progression after cataract surgery. ... The most substantial difference was seen in patients converting to wet AMD within 2 years of cataract surgery in study Six.8
S. Bressler, a co-author of the Dong et al paper in the JAMA Ophthalmology paper cited above, also spoke at the COPHy Conference and acknowledged "inconsistent findings" in the literature. He stated that
Both cataract and macular degeneration are common age-related diseases. Many individuals simultaneously manifest both conditions. The literature contains inconsistent findings describing adverse relationships between performance of cataract surgery and development and progression of AMD. 8a
There appears to be is a growing consensus that the best choice is to use blue blocking lenses to protect against blindness from AMD after cataract surgery, as indicated by the paper Ultraviolet or Blue-Filtering Intraocular Lenses: What is the Evidence?[10] which stated:
"With the arrival of blue-filtering intraocular lenses (BFIOLs) in 1990's, a further debate was ignited as to their safety and potential disadvantages. ... The potential disadvantages raised in the literature over the last 25 years since their introduction, regarding compromise of visual function and disruption of the circadian system, have been largely dispelled. The clear benefits of protecting the retina from short-wavelength light make [blue-filtering intraocular lenses] BFIOLs a sensible choice"9
While there is extensive supporting evidence that blue light exposure will accelerate the development of AMD in people who have had cataract surgery, to date the evidence is not sufficient to establish this as proven. As the authors below note, it is unlikely that valid studies will yield definitive results regarding the relative importance of blue light exposure to advancing the development of AMD in people after cataract surgery. From a discussion of Blue-light-filtering IOLs and phototoxicity.
Oxidative stress refers to tissue damage by unstable molecules known as reactive oxygen intermediates (ROIs). These compounds include free radicals, hydrogen peroxide, and singlet oxygen. The retina is especially susceptible to oxidative stress as it has the highest oxygen metabolism in the mammalian world, and because it is exposed to irradiation (ie, visible light), which is known to increase production of ROIs. Of the visible spectrum, high-energy short-wavelength visible light is the most injurious in terms of ROI production. Further, the retina is particularly vulnerable to damage by ROIs because of the high concentration of poly-unsaturated fatty acids (PUFAs) in the outer segment membranes of the photoreceptors, as PUFAs contain readily accessible electrons in their double bonds. As a consequence, it has been hypothesized that oxidative stress and cumulative lifetime exposure to visible light are important factors in the pathogenesis of AMD, and this hypothesis is consistent with the proven benefits of antioxidant supplements in terms of retardation of disease progression.
Valid studies designed to investigate the relative importance of retinal exposure to short-wavelength visible (blue) light following cataract surgery are unlikely to yield definitive results, as it would be impossible to control for the cumulative exposure to such visible wavelengths before surgery, which would be dependent on a plethora of variables including the age of the patient at the time of surgery, the duration and extent of the yellowing of the lens opacity, MPOD, amongst other factors. In other words, the hypothesized photoprotective benefits of implanting blue-light-filtering IOLs at the time of cataract surgery is unlikely to be either proven or refuted. ...Of note, implantation of UV-only filtering IOLs at the time of cataract surgery in 1167 of 4577 AREDS participants with intermediate age-related macular degeneration (AMD)... was not associated with progression to advanced AMD10
Users of bright light therapy or blue light therapy should determine whether its worth the increasing the risk of an earlier onset of blindness from AMD by continuing to use those products, or whether they should convert to a safe and comfortable Lo-LIGHT therapy lamp with low-intensity GreenLIGHT technology that does not risk retinal damage.
REFERENCES
1)
The Relationship of Cataract and Cataract Extraction to Age-related Macular
Degeneration: The Beaver Dam Eye Study Ophthalmology. 2012 Aug; 119(8):1628–1633.
Barbara E. K. Klein, et al.
2)
Risk of Age-related Macular Degeneration 3 Years after Cataract Surgery:
Paired Eye Comparisons. Ophthalmology. 2012 Nov; 119(11):2298-303.
J.J. Wang et al.
3)
Prevention of Increased Abnormal Fundus Autofluorescence with Blue Light–Filtering Intraocular
Lenses J Cataract Refract Surg. 2015 Oct 12.
H. Nagai et al.
4)
Progression of Age-Related Macular Degeneration After Cataract Surgery
Arch Ophthalmol. 2009;127(11):1412-1419.
)
L.M. Dong et al.
5)
Is the Risk of Incidence or Progression of Age-Related Macular Degeneration Increased After
Cataract Surgery? Arch Ophthalmol. 2009;127(11):1528-1529
Barbara E. K. Klein.
6)
Age-Related Maculopathy and the Impact of Blue Light Hazard
Acta Ophthalmology 2006 84(1):4-15
P.V. Algvere
7)
Ocular Risk Factors for Age-Related Macular Degeneration: The Los Angeles Latino Eye Study
Am J Ophthalmol. 2010 May; 149(5): 735–740.
S. Fraser-Bell
8)
The Course of Maculopathy after Cataract Surgery in Patients with Early Dry Amd
A. Pollack
8a)
The Effect of Cataract on Macular Degeneration
S. Bressler
9)
Ultraviolet or Blue-Filtering Intraocular Lenses: What is the Evidence? Eye Feb 2016; 30:215–221.
S. M. Downes
10)
The Evidence Informing the Surgeon’s Selection of Intraocular Lens on the basis of Light
Transmittance Properties Eye Feb 2017; 31:258–272
X Li, D Kelly, J M Nolan, J L Dennison & S Beatty
