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Myths about UV and Blue Light Filtering IOLs

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Dr. Anurag Shrivastava
D.O.,M.S. F.C.L.I

BLUE-LIGHT filtering IOLs have been unnecessarily given importance for their colour and scotopic visual performance. The role of these IOLs in protection against effects of ultraviolet-blue retinal photo toxicity is yet to be proven.

Dr Anurag Shrivastava, Eye Care & Lasik Centre, Indore has an analysis

“There is currently no study in the published scientific literature that proves any relationship between blue light and retinal damage. However, blue light definitely affects colour vision and scotopic vision, which are not attributes that we want to give up without more convincing evidence”

Introduction

As we all know that the UV light can be divided into

  • UV-A (400-320 nm)
  • UV-B (320-286 nm)
  • UV-C (200-286 nm)

Out of this UV-B has a potential risk factor in a wide range of ocular pathologies such as lid cancer, pterygia, climatic droplet keratopathy and cortical cataracts. It is also known to accelerate the inflammatory pathway in diseases such as cystoid macular oedema, uveitis and vasculitis. It is a surprising fact that,

  • UV-blocking lens cuts out 99 per cent of the UV light
  • Only one per cent of the UV gets into the eye

The cellular damage arising from UV exposure is :

First

  • Chronic low-dose damage as a result of Sun exposure over the course of lifetime;

Second

  • Acute high-dose damage from abnormally high levels of UV in particular environments such as a welder, or a surgeon, working under an operating microscope, person exposed to snow in mountains etc.

Most of the UV-B is absorbed by the cornea and lens of the eye; therefore it can cause damage to these tissues but will not normally damage the retina, because it hardly reaches retina.

ARMD AND BLUE LIGHT

One will be surprised to know that, primary drivers in the pathogenesis of ARMD are

  • Genetics
  • Smoking
  • Diet

Out of 63 studies conducted on ARMD, to show an association between blue light and macular degeneration, none of study has ever proven a relationship between two.

In fact, two studies (Rotterdam study and New South Wales, Australia study) have actually ended up showing the reverse, that blue light reduced the risk of macular degeneration.

Of those 63 studies, about one-third of them did show a connection between ARMD and visible light. “If we have a genetic predisposition for macular degeneration, then chronic low-dose exposures to light over the course of lifetime may accelerate ARMD because it makes the photoreceptors turn over faster and wears them out.

So we should protect our self from bright light levels. Therefore it is not a question of blue light, but of all light levels being responsible.

YELLOW IOLS AND COLOUR VISION

A big myth is that a yellow intraocular lens designed to filter out blue light does not affect colour vision. The fact is that the lens would not look yellow if it didn't affect colour vision. It's just like a pair of yellow sunglasses, which has to affect colour vision. The lens should be clear if it has no effect on colour vision.

Yellow lens mimics yellow crystalline lens of a 55-year-old person. But Studies have also shown that the best performance of the human eye in colour perception is around age of 19 years and as age advances it gets worse because of yellowing of the crystalline lens. So by the time we approach 55yrs, we have lost 35 per cent of our colour vision in the blue range.

A study by Greg Jackson MD and Randy Olson MD found a decrease in scotopic vision with blue-blocking lenses, because scotopic sensitivity (dim light, rods) is more dependent on violet and blue wavelengths than the photopic sensitivity (bright light, cones).

The lens has to be clear if we want no effect on colour vision.

DIFFERENT COLOUR FOR DIFFERENT VISION

Gray is the traditional aviator's choice, as dictated by the military specification for pilots, because it offers the least color distortion.

Brown filters out some of the blue portion of the spectrum but makes greens and reds appear brighter. Tests show that brown is also good for increasing contrast sensitivity while leaving colors true.

Green is said to have characteristics similar to that of the natural color sensitivity of the eye. They maintain contrast and supply clarity, reducing visible light but not interfering with color vision.

Yellow is good for sunny conditions & will make things seem brighter and clearer and increase depth perception when it's overcast. They are often used for "shooter's glasses" for this increased depth perception in bright light.

Red / pink provides glare reduction, eliminating blue light haze while brightening and enhancing vision

CONCLUSION

  • UV-blocking lens cuts out 99 per cent of the UV light one per cent of the UV still gets into the eye.
  • Most of the UV-B is absorbed by the cornea and lens of the eye; therefore it can cause damage to these tissues but will not normally damage the retina, because it hardly reaches retina.
  • A yellow intraocular lens designed to filter out blue light does affect colour vision.
  • The yellowing of crystalline lens is a bad side effect of exposure to light over lifetime, not a protective phenomenon.

There is currently no evidence to support claims that blue-light filtering IOLs can help in the prevention of age-related macular degeneration (ARMD) and other retinal pathologies.