If you’ve been diagnosed with cataract, you may be wondering if all treatment surgery is the same. The answer is no. Outcomes depend on several factors including the experience and expertise of the surgeon. One factor that is often overlooked is the role of the intraocular lens itself in protecting the eye from disease of your macula.
What do IOLs do?
The natural crystalline lens in your eye does two things; first, it focuses light onto your retina. Second, it yellows gradually with age, providing increasing protection from UV and, particularly, blue light, which can harm the retina and macula at the back of your eye. Cataract surgery involves the removal from your eye of the cloudy natural lens (itself damaged from years of exposure to UV light among other things) and its replacement with a tiny artificial lens called an intraocular lens or IOL.
The role of the IOL therefore is two-fold: to focus light onto your retina and to simultaneously protect the retina from the harmful effects of UV light and blue light. IOLs block UV light but many do not block visible blue light.
So when your natural lens is replaced with an IOL, straight away there is a significant increase in blue light exposure to your macula.
Is a good or bad thing?
Blue light and your macula
Most people are familiar with the effects of UV light on the eye. Prolonged exposure to UV light can cause damage to your sclera (white of your eye) by causing pterygium, and to your crystalline lens – by causing cataract. (This is why we should wear sunglasses). The wavelength of UV light is short and cannot penetrate deeply into the eye, thus causing its damage near the surface. Visible blue light sits next to UV light on the spectrum. It has longer wavelengths than UV and can penetrate more deeply into the eye, impacting the retina. Blue light is present inall visible light and in particularly high levels in the light emitted from the LED screens of modern TVs and digital screens.
While the exact mechanisms of blue light toxicity to the macula are not clearly understood, studies over decades have shown that damage is caused to retinal and macular cells by short, high-intensity light exposure.
Does blue light do any good things? Visible blue light is important in the circadian rhythms of your body – how you wake up and fall asleep. But studies have failed to show any difference in sleep pattern between patients with blue-blocking IOLs and those without blue-blocking. A recent study summarised the results of 56 clinical studies and concluded that while the exact benefits of blue-blocking IOLs remain unclear, they do not cause any problems with vision or sleep.
Why are blue-blocking IOLs important?
Your macula is the most critically important part of your retina. It provides your central vision, for recognising faces and reading print etc. The health of your macula deteriorates normally with age, but for 1 in 7 people over the age of 50, age-related macular degeneration (ARMD) can occur.
Some people are more at risk of ARMD than others, and your optometrist is a good person to talk to about your particular risk. Many of the risk factors, you cannot do anything about – such as age, race and family history. But other factors, such as smoking and diet can be influenced by your choices.
One of these risk factors is your exposure to UV and blue light. By having a blue-blocking IOL replace your natural lens during cataract surgery, you eliminate the risk of blue-light exposure contributing to the development of ARMD in your eyes.
What can you do?
A landmark study in Nature concluded that blue-blocking IOLs should be used routinely in cataract surgery. Talk to your surgeon about the type of IOL they plan to use for your procedure. Blue-blocking IOLs are widely available and can mean increased protection against ARMD, especially if you are in a high-risk category.