Blue-light Filtering Intraocular Lenses Sally Blackmore-Wright 1 and Frank Eperjesi 2 1. Senior Optometrist, Optometry Department, University Hospitals Coventry and Warwickshire, UK; 2. Head of Optometry, Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, UK Abstract Blue-light filtering intraocular lenses are purported to reduce the incidence of potentially damaging UV and blue light on the retina. This article reviews their background, the proposed benefits on long-term eye health and the possible disadvantages on circadian rhythm, scotopic vision and colour vision. Keywords Age-related macular degeneration, blue-light filtering, circadian rhythm, intraocular lenses, light hazard, retina, ultraviolet Disclosure: The authors have no conflicts of interest to declare. Received: 9 February 2012 Accepted: 16 March 2012 Citation: European Ophthalmic Review, 2012;6(2):104–7 Correspondence: Sally Blackmore-Wright, Optometry Department, University Hospitals Coventry and Warwickshire, Coventry, CV2 2DX, UK. E: sally.blackmore@uhcw.nhs.uk Cataract surgery is a commonly performed surgical procedure. The ageing population and the bilateral nature of the condition correlate with the increasing number of extractions. For example, in 2009, 345,000 cataract operations were performed in England. This is a substantial increase on the 230,000 procedures that were undertaken in 2000. 1 In the early days of cataract surgery, intraocular lenses (IOLs) transmitted all incident radiation. Although the cornea prevented wavelengths less than 300nm from entering the eye, 2 all other radiation was transmitted to the posterior ocular structures. The incidence of ultraviolet (UV) light on the retina gave rise to symptoms of erythropsia, with images having a red-tinged appearance. 3 To reduce erythropsia, from the early 1980s onwards, UV filters were incorporated into the intraocular lens (IOL) material. 4,5 This gave benefits of preventing potentially damaging radiation from reaching the posterior eye and improving image quality without removing longer wavelengths used in vision and other biochemical process. 6,7 The manufacturers of IOLs have now extended the concept of filtering radiation to include short-wavelength blue light (400–500 nm) from the visible spectrum. Blue-light filtering IOLs attenuate wavelengths up to 500 nm. They are readily available to surgeons but at a higher cost compared to standard UV-only blocking lenses. However, there has been controversy as to the extent of any benefit these IOLs provide and there are suggestions that they may have a detrimental effect on vision and the circadian rhythm. Light Hazard With high oxygen levels and constant absorption of radiation in the form of light during waking hours, photo-oxidative reactions occur within the retina and choroid. UV and visible wavelengths up to 600 nm are capable of photochemically damaging the retina, with short-wavelength radiation being more damaging than long-wavelengths. 2,3,8–10 Photo-oxidative reactions are risk factors for age-related macular degeneration (AMD), choroidal melanomas 11 and other posterior pole pathologies. The eye attempts to limit the effects of phototoxicity by shedding photoreceptor outer segments, synthesising antioxidants such as lutein and zeaxanthin within the retina and producing light absorbing pigments such as melanin within the retinal pigment epithelium (RPE) and choroid. 12 The ageing eye is less likely to be able to sustain these protective mechanisms leaving the eye prone to phototoxic damage. 2 Lipofuscin is a phototoxic pigment, which naturally accumulates within the retina as the eye ages. It has a peak absorption at 430 nm. 13 Photons absorbed by lipofuscin molecules are raised to an excited state and this results in the production of reactive oxygen species such as singlet oxygen and superoxides as well as free-radicals. Reactive species damage ocular tissue at a cellular level and this reduces the ability of the RPE cells to regulate photoreceptor cell turnover. Eventually the photoreceptors undergo permanent and atrophic damage. 2,7 The crystalline lens provides some protection against phototoxicity. In the first three years of life the lens is clear, gradually becoming yellow over time. Pigments comprised of 3-hydroxyl kynurnine are deposited in the lens, particularly in the lens nucleus where UVA (315–400 nm) and UVB (280–315 nm) are absorbed. 2 These pigments, often referred to as chromophores, absorb light wavelengths between 300 and 400 nm preventing UVA, most UVB and some blue-light from reaching the retina. A 53-year-old healthy crystalline lens will allow 75 % of 470 nm blue light to be transmitted, whilst a 70 year old allows only 25 %. 14 Studies have shown that transmission of blue light through the crystalline lens decreases by 0.7–0.8 % per year because of chromophore deposition. 15 If the crystalline lens is removed this protective filter is lost. In an attempt to mimic the protective yellow pigments of the crystalline lens, some manufacturers include chromophores within the plastic polymer of the IOL. These yellow IOLs are marketed as imitating the ageing eyes’ natural defence against short-wavelength light. Anterior Segment Intraocular Lenses/Presbyopia © TOUCH BRIEFINGS 2012 104 DOI: 10.17925/EOR.2012.06.02.104