Since I am an Optometrist who is practising spectacle dispensing, I was once asked by a close friend of mine, “How effective are the blue block lenses? Do they help if one spends a lot of time on screen?
To understand this, one must have some basic knowledge about light and colour. During our school days, we have been taught that white light consists of seven colours, “VIBGYOR”, of which the violet to blue have higher energy being closer to the UV spectrum.
Understanding the light spectrum
It is important to note that the entire blue spectrum (450 to 500 nanometres) is not hazardous to the eye. It is more of the violet-blue light (415 to 455nm) which is thought to cause damage to the cells at the back of the eye. It is common knowledge that if the radiation’s energy levels are higher than what the tissue can bear, it begins to malfunction and it degenerates sooner than it would with age.
Figure 1: Blue light in the visible spectrum
Photo URL: https://www.shutterstock.com/image-vector/spectrum-blue-light-ray-on-white-1777977224
Science has proved that excess exposure to UV light can cause skin cancer. Studies conducted in the laboratories have shown that high-energy blue light tends to reduce the functioning and alters the structure of the tissues in the eye. This exposure may cause cataract or macular degeneration at the retina earlier than usual.
One important point to note is the closer you get to a source, the stronger the radiation; hence it is essential to maintain a reasonable distance from the source.
Sources of blue light-emitting devices in our daily lives
• Incandescent lights emit a very low amount of blue light
• Fluorescent lights emit about 25% blue light
• Halogen lights emit low levels of blue light
• Cool white lights (LED bulbs, computer screens, tablets and smartphones) are the highest emitters of blue light(35%)
Should you wear blue light protecting lenses?
Yes, I recommend blue block lenses as I believe in the practice that “Prevention is better than cure”. The optical market has a wide range of blue protect products costing between INR 500/- to about INR 4000/-.
Is there a difference between local and branded blue control lenses?
Yes, there is a difference. The economical ones (cheaper ones) are blocking a large portion of the blue light that is required (essential) for the perception of light and colour. In these lenses, the lens material absorbs the blue light whereas the better quality ones (more expensive ones) deflect the specific harmful blue light off from the anti-reflective coated surface of the spectacle lens allowing a better perception of light and colour.
Figure 2: Blue block lens deflecting the blue rays away from the eye
How does one know if the lenses are blocking the Blue light?
From a layman’s view, rays of blue light, when blocked to pass across the lens, induces a bit of a yellowish tinge to the white light or the sheet of paper you are looking at. The more amount of blue light you cut off, the more yellowish the light or the sheet of paper would appear.
There is a simple device (made by Zeiss) at a few optical stores to provide you information about how much percentage of harmful blue light is blocked.
If not glasses, how else can I protect myself from blue light?
A simple tip to protect your eyes in case you do not have blue protect lenses and spend a lot of time on gadgets would be to switch on the “Night mode”. The night mode gives the screen a little yellowish appearance.
Blue light and sleep
There is another interesting fact to note about the blue light affecting an individual’s sleep pattern notably in those who spend a lot of time viewing the screen of computer monitors or smartphones, especially at bedtime. The blue light around the 480nm wavelength affects the secretion of melatonin, a hormone. This hormone induces sleep in a person and is responsible for the sleep-wake biological cycle called the ‘circadian rhythm.’ The blue light confuses the brain by tricking it, saying it is still daytime and hence the melatonin is not secreted. This prevents the person’s body to understand that it is time to rest.
Blue light and eye strain
During this COVID era, where online classes and working from home have become the new norm, I often get patients to my clinic complaining about eye strain and fatigue that is associated with mild redness of the eyes and a mild ache around the eyebrow region. Many of them have pre-set mind that if they wear a blue block lens, these symptoms will be reduced or stopped.
My way of managing such cases where they have already concluded that they will get relief from blue block lenses, I support their decision as there is no harm caused.
Their eye strain is not majorly due to the blue light, but it is due to overworking their delicate muscles of the eye so that they remain in focus for many hours with a reduced blink rate.
I manage these cases by prescribing the proper spectacle correction with blue protect lenses. I also advise them to be conscious of their blinking. It is best to blink at least 15 to 20 times per minute. Besides, it is a good practice to look away beyond 20 feet distance and focus on an object for about 20 seconds once every 15 to 20 minutes while working or during online classes. This will indeed reduce their eye strain.
Figure 3: Eye strain and fatigue are common after long hours of gadget work
Does blue light increase spectacle power?
Parents are often over-cautious of their children being exposed to blue light which is causing a rapid increase in power. To the best of my knowledge, there is no study to prove it. Yet, there is enough proof that excess indoor activities,( majorly through gadgets or reading books) can cause rapid myopia progression.
Every eyecare practitioner is aware today that excess near vision causes an increase in power in children rapidly as compared to the children who spend a lot of time outdoors in the sunlight.
To summarize, the blue-light protection lenses protect the eyes from harmful visible blue light, which may affect the eyes from early cataract changes and early onset of macular degeneration in the retina.
Most often, when they see a slight increase in power, the parents of children say ‘this is due to excess mobile phone usage’, referring to the bright light they are exposing their eyes to.
It is correct because it is a task at a close distance to the eye, which is known to contribute to an increase in refractive power. However, it is also true that the bright light or blue light has nothing to do with the increase in power.