I have never implanted a coloured IOL. My basic philosophy is that coloured IOLs aren't any good, and could in fact be damaging rather than beneficial. I would certainly never have one implanted in my own eye. Claiming that blue light is harmful and should be blocked is nothing more than a marketing ploy backed by absurd arguments, which have no basis in scientific fact.

In the last 30 or 40 years, there have been over 60 epidemiologic studies researching light energy and its effect on the eye. Although these studies implicate a harmful role of light, such as macular degeneration or vitreous detachments, the harm is always caused by the total amount of light exposure. Not a single one of those studies has been able to prove a relationship to blue light, only to total light exposure: when you look closely at the articles, the correlation with blue light is always just an unproven supposition from the author. There are, however, two studies showing that blue light benefits the eye.^1,2

Blue blockers do not reduce macular degeneration risk

A correlation between total light exposure and macular degeneration exists, but even then, only in those who are genetically predisposed to developing macular degeneration: those whose retinal pigment epithelium (RPE) is programmed to wear out and stop functioning before death. In this subset of genetically-predisposed people, light exposure can hasten this process — just as certain pale-skinned patients are more likely than dark-skinned patients to develop skin cancer if they spend a lot of time in the sun — but there is absolutely nothing to prove that normal, environmental levels of blue light are any more damaging to the retina than any other kind of light.

If a blue blocking lens has been implanted, macular degeneration will nevertheless continue to accelerate, because it's the total amount of light exposure that's harmful, and blue blocking lenses do nothing to protect against the full spectrum of light. The best protective device is simply to wear sunglasses and/or a baseball cap to protect the eyes from bright sunshine. Antioxidants, such as selenium and vitamin C, have also been implicated in retinal protection; taking these is an effective supplement to reducing light exposure to decelerate retinal degeneration. Once these two measures have been taken, there's nothing else to be done, other than to minimize total light exposure.

Patients are more prone to injury

In addition to not providing adequate protection to the eyes, patients implanted with blue-blocking lenses are in fact more vulnerable to injury from falling, such as hip fracture, in low-threshold light (for instance, at night-time) when blue light is more prevalent than other kinds of light. At night, wearing blue-blocking lenses is akin to wearing sunglasses, with the exception that they can't be removed — patients who have had these lenses implanted are less able to distinguish shapes in the dark and are therefore more prone to falls.

The lab studies that appear to demonstrate the harmful effects of blue light instead show something else: that blue light is higher energy than red light, but we already knew that. Exposing RPE cells to 100 times the amount of light you'd get from looking at the sun for three minutes, without the mediation of the cornea or any other barrier, shows that blue light is more damaging than red light, but that's simply because blue photons have more energy than red photons, which we already knew. What they have been unable to demonstrate is that environmental levels of blue light cause substantial damage to the retina.

A yellow lens is an aged lens

Another often-advanced argument in favour of blue blocking lenses is that, as the crystalline lens ages, it begins to yellow. This change is frequently interpreted as a protective mechanism, but this is no truer than that the wrinkling of the skin or the thinning of the bones is a protective change: it's just ageing.

What's really happening as the lens yellows is this: the RPE, which is a terminal cell and therefore cannot regenerate or replace itself, is like the garbage collector of the retina. When the lamellae slough off the photoreceptor cells, the RPE disposes of them. In patients with macular degeneration, it is not the photoreceptor cells that fail but the old, worn-out RPE that starts to lose its ability to dispose of these lamellae. These then begin to build up in the form of, for example, lipofuscin, causing yellowing, which is an indication that the RPE cells are failing, and leading to retinal deterioration.

The fact of the matter is that human beings reach their physical peak at about 19 years of age, in every organ of the body. If a lens replacement is necessary, it makes sense to put in a lens that mimics the lens of a 19-year-old, which is a clear lens, rather than the yellowing lens of a 55-year-old, which blocks blue light. You wouldn't put an old heart in a transplant patient if a younger one was available, and you wouldn't perform a skin graft with wrinkled skin, so why would you implant a lens that effectively mimics a mild cataract?