Published 04 Feb 2019
When it comes time to selecting a new pair of glasses, more often than not, finding the right frame is the easy part! Choosing the right lens on the other hand, is a whole different ball game. Bifocal lenses, progressive lenses, extended focus lenses, transition lenses, polarized lenses, multicoats, UV coatings; the options often seem endless and can be incredibly confusing.
GMHBA Eye Care Optometrist Daniel Strachan addresses some of the common queries we hear when it comes to lens design and options, and in doing so gives you the information you need when it comes to selecting your new glasses.
“I’ve recently turned 40 and I’m noticing I have to hold things further away when reading to make it clear. What’s happening to my vision?”
From the age of about 40, most people will start to lose their ability to focus on things up close. This is called presbyopia. A key sign that you may have reached presbyopia is a need to hold reading material further away in order to improve clarity. Patients may also find themselves squinting and experiencing headaches and eye-strain with close work. While this can often seem quite frustrating and inconvenient for many patients, there are a variety of spectacle and contact lens options to restore and improve near vision.
“What options are there to help me?” Luckily, there lots of options for people to correct presbyopia. As well as contact lenses, there are several lenses to suit your needs.
Single vision lenses
Single vision lenses provide clear vision at one distance and one distance only. If you have single vision reading glasses, these should bring things into focus up close, however looking far into the distance will likely be very blurry. While many people appreciate having a whole spectacle lens dedicated to reading, others can feel inconvenienced by having to take their reading glasses on and off all the time. One minor disadvantage of wearing single vision glasses is that it’s very easy to pop them on your head when you don’t need them, and then find yourself looking everywhere for your glasses later!
Bifocal lenses
These lenses are designed to provide both clear distance and near vision without having to change or remove spectacles. Bifocal lenses have two distinct sections, a top part providing correction for distance vision, and a lower half for near. There is a visible line separating these two sections. While bifocals are generally considered more convenient than single vision readers, patients may still have difficulty with intermediate working distances, such as computer tasks or reading sheet music. Another disadvantage of bifocals is the visual distortion that is created by the line separating the two sections. This can be quite problematic for patients with mobility issues or who are unstable on their feet.
Multi-focal or progressive lenses
The main advantage of multi-focal (sometimes called progressive) lenses over bifocals is that they provide the wearer optimal clarity at multiple viewing distances (distance, intermediate and near), not just one or two. Because they have no line separating the different lens sections, they look like single vision lenses and for this reason are cosmetically more appealing than bifocals. The only minor disadvantage of this lens type is that it can take the eyes and brain some time to get used to, given that they include multiple working distances.
“What is an anti-reflective coating?”
An anti-reflective coating can be applied to the surfaces of your lenses to reduce reflections and unwanted glare. There are numerous types of anti-reflective coatings out in the market, some more advanced than others. Most entry level anti-reflective coatings will block reflections and glare, but this may only be applied to the front surface of the lens, leaving the back surface exposed. Premium anti-reflective coatings on the other hand will often be applied to both front and back surfaces, and can also incorporate filters that block out harmful UV light form the sun, and high-energy blue light from electronic devices.
In order to fully protect your eyes from the sun, we would always recommend a UV filtering anti-reflective coating on both front and back lens surfaces.
“What is the difference between polarized and non-polarized lenses?”
When we are talking about lenses being either polarized or non-polarized, we are generally referring to sunglasses. All good quality sunglasses will prevent unwanted UV exposure to the eye, but the level of glare you experience will depend on whether your sunglasses are polarized or not. Non-polarized lenses are typically just tinted or darkened lenses which reduce brightness. Most types of lenses can be made with a non-polarized tint on them. Polarized lenses on the other hand also reduce brightness but are much more effective at eliminating glare. They work by filtering and blocking out light that is reflected off surfaces. This makes them great for a variety of outdoor activities such as boating, cycling, golfing etc.
While polarized lenses sound terrific in theory, there are some situations where they may be a nuisance or are not advised. For example:
- certain screens e.g. mobile phones, modern car dashboards, cannot be viewed when wearing polarized lenses.
- pilots are forbidden from wearing polarized lenses as it prevents them from being able to see sunlight reflecting off the windscreen of oncoming planes.
- polarized lenses are not recommended for skiing as they may prevent a skier from seeing light reflecting off a hazardous patch of icy snow.
“What is the best way to protect my eyes from the sun?”
Good quality sunglasses are vital when you are outdoors. These can be either polarized or non-polarized. To minimize UV exposure to your eyelids and lashes, a close-fitting wrap around style of sunglasses is encouraged. Ensuring your everyday clear glasses are made with a front and back surface UV filtering anti-reflective coating is another way you can reduce your risk of UV exposure.
“What about the lenses that turn into sunglasses when I go outside?”
Photochromatic lenses, also known as transition lenses or adaptive lenses, are lenses that change colour and darken in response to UV exposure. This means that while you are inside your lenses will be clear, and as soon as you head outside your lenses will darken like magic. This is a convenient lens option as wearers generally don’t have to worry about swapping to and from sunglasses throughout the day. They also won’t activate in the car as windscreens are designed to block out UV light.
We hope this has answered some basic questions regarding lens designs and lens options.
If at any time you feel your eyesight has changed or deteriorated, we encourage you to contact your optometrist or local GMHBA Eye Care practice. Your optometrist or optical dispenser will be able to conduct an eye examination and if needed, advise you on the lens design and lens options that will best suit your needs and lifestyle. The GMHBA Eye Care team have also prepared these helpful hints for picking the right frames for your face.
About the author
Daniel Strachan completed his optometry degree at Deakin University in 2015. Prior to this he obtained a Bachelor of Commerce / Bachelor of Science double degree through Monash University in 2008. Daniel’s decision to become an optometrist was made easier by the fact both his parents are optometrists (so too was his grandfather). Daniel enjoys all aspects of optometry but has a keen interest in contact lenses and kids’ vision.
