Weighing the Evidence for UV Filters in IOLs

Dermot McGrath reports from the French Society of Ophthalmology Annual Meeting

Although intraocular lenses have incorporated filters to block harmful ultraviolet (UV) rays since the 1980s, the debate about exactly which wavelengths of visible light should be blocked continues to animate the scientific community.

Speaking at the virtual annual meeting, Professor Corinne Dot MD, PhD, FEBO, said that while all modern IOL platforms block harmful UV light, there are major differences in the ultraviolet transmission characteristics of the wide range of lenses currently on the market.

“We know there are key differences between the implants thanks to studies such as that by Dr Carmen Garcia-Domene [Optom Vis Sci. 2018 Dec; 95(12): 1129–1134], which looked at eight different IOLs with UV blockers. The real question is whether the differences in the filtering capacity of the lenses are clinically significant,” she said.

Reviewing the history of UV filters in IOL technology, Prof Dot said the goal of the filter on the implant is to essentially reproduce the natural filtering characteristics of the crystalline lens.

“In the 2000s, it was demonstrated that certain parts of the blue light spectrum were more toxic for the retina compared to other blue light wavelengths, which are important for biorhythms and sleep patterns. This gave rise to yellow implants that block blue light in the spectrum of 400 to 430 nm, which is supposedly the most toxic to the retina,” she said.

Prof Dot identified three main types of filters in current use: ultraviolet filters (white IOLs) available since 1985 that block all UV from 300 nm to 400 nm; yellow implants that block all UV and part of the blue light spectrum, available since 2003; and the more recent violet light-filtering IOLs that block violet light in the range 300 to 400 nm and part of the blue light spectrum.

Prof Dot said pooled findings from the Beaver Dam and Blue Mountains Eye studies showed the AMD risk increased by a factor of 5.7 after five years for aphakic patients who received cataract surgery compared to those with implants incorporating a UV filter.

“It clearly shows the interest of having UV blockers, even after a certain age,” Prof Dot said.

The picture is more complicated when it comes to establishing the utility of using yellow blue-light filters in IOLs for macular protection.

“A 2018 Cochrane review [Downie et al, Cochrane Database Syst Rev. 2018;5] which included 57 randomised control trials from 17 countries and more than 5,000 eyes, concluded macular protection was not clearly established for using a blue-light filter, nor was its influence on the development of AMD or its progression,” she said.

However, a subsequent publication by the same authors pointed out that most of the trials included in the initial review had a very short follow-up of fewer than three months, and drawing conclusions about AMD risk was therefore impossible.

“Companies have no real commercial interest to conduct long-term investigations, hence register or institutional studies might represent the best avenue to shed light on these important questions. We also need to bear in mind that AMD is a complex multifactorial disease, with tobacco, genetic factors, diet, and other environmental factors all playing a potential role,” she said.

Prof Dot cited a recent single-centre retrospective study in Finland of more than 11,000 eyes which looked at two groups of patients with either yellow blue-filtering or standard white IOLs implanted after cataract surgery from 2007 to 2018 with an average age of 75.4 years (Achiron et al, Ophthalmology, 2021 Mar; 128(3): 410–416).

“No benefit was found in yellow blue-filter IOLs versus standard white IOLs for the incidence of AMD after surgery—or on the outcome of patients already being treated for AMD in terms of number and interval of intravitreal injections or on the evolution of AMD. However, Finland is not a sunny country, so there is a real interest in conducting similar studies further south,” she observed.

For potential toxicity from LED lights, Prof Dot said there was no present evidence that they pose a risk to the retina. “LED may be uncomfortable for some but are not considered dangerous at this point, so there is no real interest in extending LED filters to IOLs,” she explained.

In terms of sleep quality, a recent meta-analysis showed it improves significantly after cataract surgery irrespective of whether a blue-light or UV filter is used (Zheng et al, Int J Ophthalmol. 2017 Nov 18; 10(11): 1734–1741).

Summing up, Prof Dot said the standard UV filter has proven its utility and is available on all implants on the market. For yellow IOLs with a blue-light filter, she said their utility is hypothesis-based rather than evidence-based. Violet filters have very few studies, as they are a recent addition to the market, but they offer an intermediate profile between UV filters and blue-light filters that may serve as a fitting compromise for those sceptical of yellow IOLs.

“We know there are key differences between the implants thanks to studies such as that by Prof Carmen Garcia-Domene.”

Corinne Dot MD, PhD, FEBO is Professor of Ophthalmology, Val de Grâce, Paris and head of the department of ophthalmology, Desgenettes Hospital, Lyon corinnedot.pro@hotmail.fr. or Corinne.dot@hotmail.fr EUROTIMES | OCTOBER 2021