Buying a pair of glasses can be a daunting experience. There are so many styles of frame to choose from and all too often little consideration is given to the lenses. Remember when buying new glasses, your choice of lens can have a major impact on your quality of vision and the overall look of your glasses. Here we explain some of the different lens options available.
Single Vision - One Lens for one function
Single vision means that you have a prescription in your glasses that is correcting for one distance, for example, for reading or long distance.
For many this is all that is required until over 40 years old when age plays a part in the eyes depth of focus abilities. These lenses can then have limitations, as sometimes more than one pair of glasses is needed.
This could cause difficulties, an example of such would be having just a set of reading lenses in a lecture or meeting environment. This is when a bifocal, varifocal or occupational lens may be considered.
The picture shows a single vision distance lens as may be experienced by someone over the age of 40 years old. Notice how the closer detail on the mobile phone is out of focus.
Bifocal - One Lens two functions, distance and near
A bifocal is used when 2 prescriptions are needed, usually for long distance and near vision ie: close reading.
Both prescriptions are put on to the same lens, with a visible line separating them.
This is a more convenient option, as there is no need for 2 single pairs of glasses.
Although, these can cause some problems with mid distance tasks such as a computer, so depending on the person’s age and tasks required, a middle distance/reading bifocal can be used.
The picture shows a bifocal lens. Notice how the closer detail on the mobile phone is in focus, and the window is in focus in the background, but the flowers in the mid distance are still out of focus. A varifocal lens would help you focus on objects at all distances.
Varifocal - One lens for all functions - the closest to natural vision
The picture above shows a varifocal lens. Notice how the varifocal lenses help you focus on objects at all distances.
A varifocal gives you all the benefits that a bifocal does, but without the visible line separating the prescriptions. It also has the added benefit of an intermediate correction in the same lens, this would be suitable for computer use. The lens starts with distance at the top, graduating down to intermediate and then reading at the bottom. Varifocals have a slight element of soft focus at the edges of the lens which is usually adapted to relatively quickly by the wearer.
At Onlookers we offer different categories of varifocals to suit the visual demands and the budget of the patients, due to newer technology, these lenses now offer wider fields of vision, more easily accessible reading areas and quicker adaptation periods than previous generations of varifocals. Our qualified Dispensing Opticians will be glad to help you decide which type of varifocal is suitable for you.
Onlookers are a Varilux Consultant Optician, and a Nikon lenswear consultant.
Basic Varifocal
(Red lines for illustration purposes only)
Varifocals have a slight element of soft focus at the edges of the lens.
Better varifocals offer wider fields of vision, more easily accessible reading areas and quicker adaptation periods than more basic varifocals.
Better Varifocal
(Red lines for illustration purposes only)
Occupational Lenses
These lenses are commonly used when a correction for near work is needed. A single vision reading lens wearer would find that anything beyond this distance would be blurred, therefore either the wearer would need to remove the glasses or switch to another pair of glasses to view mid distance. Mid distance could be anything from using a computer to eating a meal.
Occupational lenses allow you to view at mid range and near distance, in the same pair of glasses, making everyday tasks easier and more comfortable for the wearer. These can be used as an additional pair to your main pair of spectacles, particularly useful for long periods of wear on a computer. Some models even offer a semi-distance area for walking around the office or house, but they do not offer a long distance correction, so are not suitable for driving.
We would also recommend an Anti-reflection coating on these lenses. Our qualified Dispensing Opticians will be glad to give you advice on these lenses.
Single Vision Lens
(Close work in focus Only)
Occupational lenses give an increased working distance at the upper portion of the lens.
The addition of an Anti-reflection coating will help to reduce eye fatigue and reduce reflections from computer screens.
Occupational Lens
(Objects on table in focus as well)
Anti-reflection coatings
Anti reflection coatings are designed to reduce the light lost by reflection off the front and rear surfaces of the spectacle lens, the higher the index of lens, the more light lost in reflection. This results in an improvement in vision of approximately 8-12% (dependent on material), this is due to the amount of extra light your eyes receive through the lenses.
Other benefits are:
- Improved cosmetic appearance as other peoples attention is taken away from unsightly reflections in the wearers lenses.
- Lenses look thinner as are less obvious.
- Safer and more comfortable Vision due to a reduction in distracting reflections.
- Also they are advantageous whilst driving at night time as they reduce dazzle from car headlights and street lighting.
- When reading, contrast is improved, and the annoying glare off the back of the lenses is reduced, which can be one of the main reasons for eye fatigue.
- Anti-reflection coating is also available on the rear surface of sunglass lenses, so light is not reflected back into the wearers eyes.
No Coatings
(Reflections in the lenses are seen)
The two images compare the cosmetic appearance of an Uncoated lens and that of a lens with an Anti-Reflection coating.
Anti-Reflection Coating
(Lenses have no reflections)
No Coatings
(Reflection and light scatter from headlights)
The two images demonstrate the visual differences between an Uncoated lens and that of a lens with an Anti-Reflection coating.
Anti-Reflection Coating
(Reduced ight scatter from headlights)
Thinner & Lighter Lenses
There are many different types of thin and light lenses (High Index). High index lenses are thinner and lighter than traditional glass or plastic and are geared towards those with moderate to high prescriptions, which can make wearing glasses more comfortable and enjoyable to wear, as they are cosmetically more appealing, this can restore confidence.
High index materials can loose approximately 15-20% of light off the surfaces of the lens, therefore the majority of thinner lenses at Onlookers come with an anti-reflection coating which allows nearly 100% of light through the lens, resulting in sharper vision. Some high index lenses can be manufactured up to 50% thinner and 40% lighter than standard plastic lenses, so gone are the days of thick heavy lenses. Plastic lenses are also a lot safer than heavy, brittle glass lenses.
Other benefits are:
- Thinner - Improved cosmetic appearance.
- Lighter - More comfortable.
- Stronger lenses - Less likely to chip, important for half rim frames.
- Stronger lenses - Less likely to break, important for rimless frames.
- Compliments lightweight frames.
- 100% UV protection.
Standard Lenses
(Thicker & heavier)
The two images compare the cosmetic appearance of standard lenses and that of a Hi-index thin & light lens.
Thinner Lenses
(Improved cosmesis & Feel comfier)
Transitions Lenses
Clear Indoors
At home, in the office or in a restaurant, Transitions lenses are as clear as ordinary lenses, indoors and at night.
Adapts Quickly
Whether cycling, walking the dog or going out shopping, they provide comfort by conveniently darkening outdoors to reduce glare and tired eyes.
Dark Outdoors Rushing between meetings, at school sports day or out in the garden, they protect your eyes by blocking 100% UV rays, 100% of the time.
Transitions® adaptive lenses are designed to be worn every day
Transitions and the swirl are registered trademarks of Transitions Optical, Inc. © 2011 Transitions Optical, Inc.
Transitions are fast acting photochromic lenses which give you automatic protection from the sun and are the ideal everyday choice for healthy sight.
They are available in most lens designs, Single Vision, Bifocal and Varifocal. They are clear indoors and at night. Outdoors, they automatically darken as light conditions change.
They provide visual comfort and enhance visual quality, helping you to see better today. And like sunblock protects your skin, Transitions lenses block 100% of harmful UVA and UVB rays helping to protect the health and wellness of your eyes so you can see better tomorrow too.
Combine Transitions lenses with an Anti-reflection coating for ultimate performance. As well as actually increasing the speed of fade back, the lenses stay much cleaner for much longer. Transitions are available in either Grey or Brown.
Transition lenses react to UV light, and as this can be blocked out by a modern car windscreen, Transitions may not darken behind your car windscreen.
To combat this Transitions have now launched “Transitions Xtractive” which will darken to approxiamately 50% behind a car windscreen. 