by Seamus Flynn, Optometrist
We have all experienced that annoying glare that comes from a computer screen or oncoming headlights when driving at night. But what causes it and how can we avoid it?
Glare occurs when you experience a discomfort or reduction in visual performance when the eye is exposed to an intensity of light that it has not adapted to. In other words when light is reflected into the eye at an angle and level that it is not ready for.
For glasses wearers it can be worse as the glare also occurs when light is reflected off the surface of the glasses lens and back into the eye.
This can be debilitating and even dangerous in some situations such as when driving.
BENEFITS OF ANTI GLARE GLASSES
The most obvious benefit of anti glare glasses (also called anti-reflective lenses) are that they reduce glare from all light sources and give much more comfortable vision without the associated side effects of eyestrain and headaches in some cases. It allows you to work for longer and more productively when using digital devices such as computer screens and has a safety element when driving at night by reducing the sometimes debilitating glare of oncoming headlights
Anti glare glasses also results in sharper vision as it allows more light to be transmitted through the lens rather than getting reflected and the more light that gets through the sharper the vision and the contrast sensitivity and the better the visual performance.
There is also a cosmetic benefit as you don't get an unsightly glare off your lenses when someone is looking at you or in photographs. Instead of seeing glare on the lenses if you hold them at an angle you will see a very slight cosmetically pleasing green or blue hue.
The coating can also extend the life of the lens by preventing it from scratching and preventing smudges from appearing on the lenses so that they have to be replaced less often.
When combined with blue light lenses they also block blue light which reduces digital eye strain and prevents tired eyes, headaches and eyestrain as well as helping regulate sleep patterns by preventing the blue light from suppressing the production of melatonin (a sleep hormone)
When driving at night anti reflective lenses are important to help reduce debilitating glare from oncoming headlights and are important for safety.
HOW DO ANTI GLARE LENSES WORK?
Anti glare glasses contain lenses that have multiple thin layers embedded in it with each layer having a different refractive index (i.e. bending light by different amounts) These layers cause the wavelengths of the glare to neutralise each other and result in more light being transmitted through the lens with only a very small percentage being reflected. This neutralisation in the glare wavelengths result in a much more comfortable visual experience and a cosmetically pleasing hue from the lens rather than unsightly glare.
HOW TO PREVENT GLARE?
The best way to prevent glare is to use anti glare glasses if you are a glasses wearer, or non-prescription anti blue light lenses with anti glare, if you don't use prescription glasses but do use digital devices regularly.
Other practical steps you can take are:
ADJUST YOUR SCREEN
If you are using a laptop or PC you can adjust the position of your screen to minimise glare. If the screen is facing an unshaded window or if the light from outside the window is shining directly on the screen then these are conditions where the user is highly likely to experience glare. Adjust your screen to alter the angle of the reflections away from your eyes. Most monitors allow adjustment of brightness so its best to align the screen brightness to the same level of brightness in the room as discrepancies here can also result in glare.
FOLLOW THE 20-20-20 RULE
This is a great guide to improve your "visual hygiene"
The 20-20-20 rule states that you should try to take a break from screen use every 20 minutes and to look away from the screen and into the distance for 20 seconds and focus on an object 20 feet away.
Making a conscious effort to blink regularly is also very important when using screens. This is because when we are doing prolonged close concentrated our eyes converge and don't blink as much as they would if we were looking further in the distance and not doing concentrated work. Because we don't tend to blink as much in these situations our eyes dry out and become strained and uncomfortable. Making a conscious to blink helps rehydrate the eyes and keep the eyes refreshed.
POSITIONING OF INTERNAL LIGHTS
The positioning of internal lights are an important factor to consider when looking to reduce glare from screens.
Artificial lights should be placed at right angles to the screen to avoid glare. The monitor can be altered for overhead lighting and desk lamps should be adjusted to create this angle also. Adjustable lights which can be dimmed and increased are also a good idea so that they can be adjusted to suit the conditions to keep glare to a minimum.
Make sure that your desk has a dull or matt finish rather than a shiny surface that will reflect light and cause glare. If possible its a good idea to alter the colours of the walls and surrounding areas to prevent glare.
GLARE AND DIGITAL EYE STRAIN
Glare, along with blue light is a major cause of digital eye strain or computer vision syndrome. Glare from the computer screen causes the pupils to constrict and rapid eye movements which are highly correlative with glare discomfort. Repeated exposure to glare can cause a stress on the visual system causing eyestrain and tired eyes. Those with cataracts in their crystalline lens suffer even more from glare from computer screens because rather than doing through the lens unimpeded, light from the screen enters the lens and is reflected off the cataract causing more glare. When using digital devices using glasses with anti blue light lenses and anti glare lenses is a great idea to reduce digital eye strain and improve visual comfort.
Anti-Glare Glasses and Road Safety
The most important situation to use anti glare glasses is whilst driving, especially if driving at night. At night we are exposed to a number of light sources such as street lighting, headlights of cars and even the internal lights in the car itself. All these light sources can cause glare which can be dangerous if it distracts the driver and affects the drivers vision. At night time our pupils dilate to adapt to the low light levels. This means what when light is shone towards the eyes more light gets in and the eyes have to adapt quickly to the increased light levels. When we get older this reflex of constricting the pupil to incoming light slows down which increases the debilitating effect of the glare. Wearing tinted lenses when driving at night is not a good solution to protect from glare as it also decreases the overall amount of light entering the eyes which will reduce the sharpness of vision. Using anti glare glasses is a much better idea as it will reflect the oncoming light away from the eyes whilst maintaining the overall clarity of vision making driving at night much safer.
Medically reviewed by Dr. Dearbhaile Collins