BLOG: IOL chromophores: What should we filter?
Among the many advancements in IOL platforms recently has been the introduction of selective wavelength filtering.
Most IOLs block harmful ultraviolet (UV) rays, but there has long been debate about which wavelengths of visible light to block. The spectrum of visible light ranges from violet to red, or from about 360 nm to more than 700 nm. The shorter-wavelength, high-energy light at the blue-violet end of the spectrum — and especially light less than 450 nm — creates light scatter, and the violet light from LED lighting has been associated with retinal damage. Our exposure to short-wavelength light in our environment has been increasing due to the proliferation of backlit electronic devices and LED bulbs in everything from lamps to car headlights. In an attempt to avoid the effects of short-wavelength light, blue light-filtering (BLF) IOLs have been in the marketplace for some time.
But blue light also has positive benefits. Daytime exposure to blue light in the 450 nm to 500 nm range is beneficial for sleep, mood and cognitive function. Blue light transmission also helps with image quality in low light, which can make it easier for older adults to safely navigate their environment at night. Unlike light-filtering sunglasses, an IOL can’t be taken off during part of the day, so we might not want to block all the short-wavelength light. Instead, filtering out just the shortest-wavelength violet light could reduce the harmful effects of those wavelengths, while preserving the beneficial effects of longer-wavelength blue light for our patients.
In a clinical study that compared bilateral implantation of violet light-filtering (VLF) IOLs with bilateral implantation of colorless, UV-only filtering lenses in 240 U.S. patients, the VLF lenses reduced LED headlight halo intensity by 29%. Additionally, significantly more patients with the VLF lenses (P = .017) said they experienced no difficulties driving at night compared with the colorless IOLs. Preclinical work, meanwhile, showed that VLF retained more scotopic vision and melanopsin function than BLF.
Our European and Canadian colleagues already have access to VLF technology with the Tecnis Synergy lens (Johnson & Johnson Vision), which combines selective wavelength filtering with chromatic and spherical aberration compensation, high optical quality and extended depth of focus. From my perspective, the potential of VLF lenses to mitigate dysphotopsia is an exciting step forward in the evolution of advanced technology IOLs.
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