Essilor Lenses: lenses for prescription glasses.
Essilor lenses with UV Protection · fog resistance · blue light protection · smudge resistance · scratch resistance · clear vision · close up vision · distance vision · Lenses for extreme conditions · Lenses for indoor and outdoor
The Varilux X lens is the result of continuous refinement since 1959 of the first version of the progressive lens (also called multifocals) to correct presbyopia now with more than 50 patents for cutting-edge progressive lens technology as a world leader.
Despite poor medicare rebates and some poor rebates from some private health insurers,and the plethora of advertising (lower cost products claiming to be the complete solution for all) that concentrates on price,many patients come to find investing in more complex and quality eyewear is worthwhile.
Often the in-store experience in the low cost advertising store that attracts some people,is one where alternative premium offerings are generally recommended way beyond the advertised claims and furthermore then are generally in line with independents as far as price is concerned. The adage compare apples with apples applies as not all lenses and frames are the same.
We can help also in choosing frames and the right lenses and to learn all about lenses,your vision and what activities need special vision for the stages of your life.
Their vision institute has enabled multifocal lenses to be more readily adopted than bifocal lenses.
The Silmo d’Or ( Salon Mondial de l’Optique 2017 (SILMO) ) award winning Varilux X series progressive lenses meet the visual needs of todays highly connected generation X presbyopes. Customisation levels :
Level 1 Tilt,wrap,BVD
Level 2 adding dominant eye,optional progressionlength
Level 3 adding centre of rotation,reading distance
Level 4 adding near vision behaviour
Varilux range
The VisiOffice system precisely measures many aspects of your eyeglasses in an as worn position that can influence the success of your prescription.
Visual performance can suffer greatly due to inaccurate centration. Wearer studies means much Essilor can gather statistical information to refine and improve the lens designs.
Our standard Rx will give us about 75% of the clarity we should have from our vision
The challenge for optical designers is correcting for higher order aberrations (including Coma,Spherical aberration and trefoil)
Spherical aberration is increased after myopic LASIK surface ablation as well as from the bigger pupil of night vision. It results in halos around point images.
Pupil size can vary eg between day and night
HOA’s could account for 20% of clarity of our vision – with 5% influence due to the tear film constantly shifting
Aberrometers have evolved and measure HOA’s in one direction of gaze but the eye will rotate behind the lens surface so centre of rotation needs to be measured for the particular eye.
The most advanced optical labs work with designs based on the wavefront exiting eg on the back surface of a progressive lens (using adaptive optics calculations) involving a pupil map – measuring the size of the pupil according to Rx, age (add), near distance and light conditions with the pupil sizes being plotted across the lens surface.
Using the Visioffice we know the position of the COR and with position of the corneal Purkinje images calculations such as the far point sphere (FPS) for the patient’s eyes so develpoped optical designs can then be recalculated according to the FPS of the patient’s eye and other wearer parameters
This can manifest paticularly with contrast sensitivity function for the wearer and larger clearer optical zones. For the customised lenses all measurements for both eyes are required even if only one lens was to be replaced as the lenses take into account binocular vision to ensure the lenses are balanced correctly.
The spectacle frame has to be tailored to fit the individual.
- Correct Frame front alignment including:
- Horizontal alignment the frame must sit level on the face
- Bridge fit needs to sit comfortably sharing the weight evenly across the nose.
- Face form angle to ensure each rim is equidistant from the eyes.
- Correct Pantoscopic angle for the face
- Avoid the rims touching brows and cheeks
- Correct Side width
- Avoid touching the sides of face/head until just in front of ears. The frame sides should not touch or rest and never press against the side of the head.
- Correct Side bow
- Sides should have a slight bow near the ears following the contour of the head at this point.
- Correct Length to bend
- Side’s turn down (hockey bend) about 2 mm behind the root of the ear.
- Correct Anatomical bend
- This needs to have the appropriate turn into the side of the head behind the ears (to create friction NOT pressure) and the temple end should follow the contour of the mastoid area to allow it rest gently there distributing the weight evenly over these undulations.
Often inferior designs and poor centrations are often at the root of poor optical performance.
Frame size depth and width and bridge design will all involve different centrations ie positioning of the lens to the eye. All spectacle frames must be custom fitted to the wearer to accommodate their facial and head requirements.
Most eyes should be situated in the top third of the frame for aesthetic balance and usability. This also allows for the lens optical centre and the centre of rotation of the eyes to be close. Very few people are perfectly symmetrical.
The correctly adjusted fitted frame will sit comfortably and should never create pressure. It should only create friction which will stop it from slipping and sliding forward so fitting lens or frame measurements can be reliably taken.
Peripheral vision is compromised with a variety of lens forms which is improved by better lenses. Optimised progressive lenses use default measurements that consider how the frame might sit on the patient’s face.
Personalised lenses incorporate specific measurements such as facial dimensions, back vertex distance, pantoscopic tilt and facial wrap of the frames,this changes the effect of the prescription by adapting the lens design and matching the prescription from its written form to the as-worn position on the face.
Computer Numerical Control (CNC) technology in the manufacturing process has been the key to producing highly accurate lens designs, known as digital or freeform surfaced progressive lenses.
Traditionally, lenses were designed with the power of progression on the front of the lens, however the advent of digital and freeform surfacing has allowed this to also be done on the back.
This has advantages of a wider field of view.Some lens companies have got 1000 or more individual value points on a lens, which is essentially like 1000 individual tiny lenses in the one lens.
Essilor’s Varilux range of lenses, spearheaded by the Varilux X Series, encompass more than 50 patents, with each individual lens incorporating up to 30 patents alone.In the traditional surfacing process, the back of the lens was cut using two curves to produce the sphere, cylinder and axis of the prescription. Once completed, the rough surface was “fined” and “polished” using a metal tool to match the two curves. Specific pads on the tools removed the roughness before making the lens transparent.
Today’s more advanced digital surfacing process,allows the back of the lens to take any form, such as an aspheric design or progressive surface. Manufacturers can also use this complex surface to overcome the shortcomings of the base curve, regardless of whether it is a simple or more complex front surface.
The surface is cut with a precision diamond tool. The design is a computer file and is generated for each lens via complex calculation software which can take into account new parameters such as the frame tilt, wrap and back vertex distance and other information that will be added into the calculations.
The surface is cut so finely that the only additional process is called ‘soft polishing’ – a gentle polishing that removes just enough material to make the lens transparent without impacting the complex surface that has just been cut.
Quality depends on
• The machinery involved to manufacture highly accurate lens surfaces.
• The process, including the operating procedures, software system, calculation engine, consumables, experience and quality control.
• The design, capturing the latest innovation in the science of sight, the source of the optical benefits to the wearer.
Some Varilux products were worn by manty thousands of people around the world in clinical trials before it went to market.
Reducing swim effects and broadening the field of vision are the most common issues optical engineers have been attempting to overcome
for decades. Essilor elevates its premium progressives, such as its top of the range Varilux Xclusiv, to the level of personalisation with the use of an iPad app that simulates the way people read without using text.It involves the patient tracking a blue dot across the screen, while the iPad camera measures the down gaze, offset from centre and the reading distance.It also factors in the patient’s visual behaviour. At one extreme keeping their eyes still and tracking with their head or, at the other, keeping their head still and tracking with their eyes – and all the combinations in between.
From this personal data the design of the lens is modified to shift their volume of vision to exactly match their parameters.
All the below progressives are Digitally surfaced aspheric / atoric back surface and the moulds for any semi-finished, therefore the front surface, are digitally surfaced aspheric
• some out of range are done with conventional surfacing otherwise
• Back surface digital surfacing with both the Rx and the progressive surface on the back is done for Varilux Comfort
• Dual Surface – i.e. part of the progressive design is on the front and part is on the back – Vx Physio and Vx X series – a specific aspheric on the front and aspheric / atoric on the back.
Xclusive allows for a min fitting height of 14 mm and a max corridor length of 17mm in 0.1mm steps.
The heights and frame parameters are measured with natural posture adopted by the Visoffice2 technology. Then the length of progression and the inset are tailored in line with the prescription, the frame measurements and the fitting parameters.
| Lens Design | Centration | Heights | Tilt and Wrap | Back Vertex distance | Head cape | Notes |
| XCLUSIVE | ERCD PD’s | ERCD Heights | √ | √ | √ | Custom PAL Length,Dominant Eye, Near Vision Behaviour Nano Optics, Synchron Eyes and Xtend Technology |
| X FIT | ERCD PD’s | ERCD Heights | √ | √ | √ | Optional length Nano Optics, Synchron Eyes and Xtend Technology |
| PHYSIO 3.0 FIT | ERCD PD’s | ERCD Heights | √ | √ | Binocular Booster Technology to prevent Image Jump and minimize Visual Distortion | |
| PHYSIO 3.0 | Monocular | Monocular | ||||
| PHYSIO F 360 NE | √ | √ | Allows for More Customization – Wrap, Tilt and BVD of the pioneer technology | |||
| PHYSIO NE | Improved Vision in Low Light design | |||||
| COMFORT 3.0 | W.A.V.E front Aberration Control | |||||
| STYLISTIC | Monocular | Monocular | √ | √ with frame base curve | W.A.V.E front Aberration Control | |
| COMFORT NE | Monocular | Monocular |
Varilux progressive lenses have continuously been improved since first introduced in 1959. Seven generations followed including
Varilux 2 (1973) to Varilux Comfort (1993), Varilux Panamic (2000),
Varilux Physio (2006) and the Varilux S series (2012).
The 8th generation X series 2018 is a breakthrough as it has an expanded field of near vision that includes “arm’s-length” vision, and the ability to customize the lens progression based on the wearer’s actual real life near-vision behaviour. In this as worn position the fitting parameters are linked so the optimised lens design can minimise some of lens aberrations that may impact on the wearer.
VARILUX X SERIES
The Varilux X series was found to benefit arm’s length vision or intermediate vision.
Also the so called volume of vision offers user friendly optical ranges allowing not just reading but multiple tasks in a near-intermediate distance between 40 and 70 cm as well as clear vision beyond those regions.
The newest Varilux X technology enables more wearer customization by Nano Optics, Synchron Eyes and Xtend Technology which address limitations due to measurement error with these accurate 3-dimensional measurements such as Pupillary Distances (Mono/Total), Fitting Heights, Natural Head Position (Head Cape), Eye Rotation Center, frame width,height, Pantoscopic Tilt, Wrap Angle,Vertex Distance, Leading Dominant Eye, Head/Eye Movement Ratio, Stability Coefficient Reading Distance.
Prescription lenes can be more advanced and personalised than ever. A frame must be properly adjusted to meet standards parameters for digitally surfaced lenses
Spectacle designs can be
1. Back surface spherical (and/or toric).
2. Front Surface Aspheric Standard fare (flatter FC for plus lenses).
3. Back Surface Aspheric Benefits atoric designs where the cylinder is on the back
4. Dual Surface Freeform High end designs where the add can be shared between both surfaces allowing them to create wider channels and reading areas
Most progressive powered lenses (PPL) have aspheric front curves,sometimes spherical
Basic and older PPL designs have conventional back curves (using spherical or toric curves) with aspheric FC. Some older designs have been rejuvenated by having the back surface digitally surfaced.
Ultra near vision & screen distance personalisation enables more comfortable digital screen use.
• People whose head/body posture is causing them discomfort while using computers and digital devices.
• People whose hobbies and leisure activities require specific correction.
Do you experience back or neck discomfort when spending prolonged time on your digital devices?
Varilux Digitime is personalised to ensure your head and neck are comfortable throughout the day.
Average distance to smartphone is 33 cm but can vary compared to standard reading distance of 40 cm whereas average distance to computer is 63 cm
Of the Varilux Digitime the Mid design is the most commonly prescribed. However the specific design chosen will be determined on the individuals needs.
Screen distance personalisation has an impact on the minimum depths of field. If the parameter is not measured, the average value (63cm) will be used to calculate the design.
The most advanced optical labs work with designs based on the wavefront exiting eg on the back surface of a progressive lens (using adaptive optics calculations) involving a pupil map – measuring the size of the pupil according to Rx, age (add), near distance and light conditions with the pupil sizes being plotted across the lens surface.
The effective power changes take place over:
- Nikon Soltes 19mm
- Nikon Home & Office 22mm
- Varilux Digitime is more compressed by comaprison over 12mm from near to intermediate / working distance power (for direct comparison with Soltes and Home and Office) and 24 mm including the Ultra near power (+0.50D for the Near and +0.25D for the Mid version +0.12D for the Room version)
Personalisation options
- Screen distance
- Mono distance PDs
- Mono height
- Wrap angle
- Pantoscopic angle
- Vertex distance
- Eye rotation centre distance
- Head cape
The newer ‘as worn’ lens designs can be optimised for the position of wear and have newer surfacing techniques including atoric designs.Older PPL designs are still available and can be provided as a budget alternative.
• Varilux Comfort – released 1992; Varilux Comfort NE released 2011; Varilux 3.0 released 2018
• Varilux Physio – released 2006; Physio NE – released 2015; Physio 3.0 released 2018
Recent low cost non varilux lenses include Quadro,Assent and Accord (though there a myriad of digitised and non digitised options) as examples of simple back surface designs and don’t offer customisation.
Digital devices eg smart phones are changing our visual needs and ranges. The typical working distances are being modified by the growing use of digital devices. Today more and more time is spent on digital devices hence the evolution of specfic lens designs.
90% of 45-65 year olds use one digital device daily and accordingly changed their visual/ postural behaviour, creating discomfort,
tired eyes and often associated neck and shoulder pain.
Near vision tasks, especially reading, are becoming even more challenging as characters are becoming smaller and digital devices are being held closer.
Digital technology usage means newer optical standards such as reading distances and eye declination have evolved.
While almost all wearers increasingly use their screens at close distance, conventional single vision lenses are optimized for far vision only. This means when wearers look at close-distance objects through the bottom of their lenses, they experience some optical aberrations.
• Eye-Device distance• Head declination• Eye declination• Head Roll (rotation of the head around an antero- posterior axis were recorded as are important in Computer Vision Syndrome (CVS). CVS has been defined by the American Optometric Association (AOA) as a combination of eye and vision-related problems due to prolonged use of computers. The combination of too much screen time and vision issues such as myopia, hyperopia and astigmatism can put extra strain on the eye. Fatigue can set in as the eyes strain to correct for vision issues while focusing on complex digital content (Vision Council 2016)
Varilux digitime near is similar to Type 1 Nikon soltes
Varilux digitime mid is similar to Type 2 Nikon soltes
Varilux Digitime Can be substituted for Soltes but not Nikon H&O. Has other benefits that Nikon do not such as power booster for smartphones.
| Lens Name | Lens Type | Fit Parameters | Height Measurements | Shifts Available | Power At Pupil | Notes |
| EyeZen | Modified Single Vision | Monocular PD’s heights, Distance Rx | Pupil heights, Min ht 15mm | 0.40,0.60 or 0.85D over 15mm | Distance Rx | For the relief of symptoms of visual fatigue brought on by long periods of close work specifically on hand-held or portable digital devices. Suitable for all people with accommodation / binocular vision issues |
| Varilux Digitime | Extended Focus | Monocular PD’s height, Full Rx | Pupil height as per Progressive lens. Min ht 18mm with some boost,24mm for entire boost | Three styles: Near = e.g. computer + mobile phone; Mid = computer + desk; Room = computer + around the office. | Customised to the wearers screen/working distance.EG for Add+2.00,screen distance 50cm.Power will be set for 50+15cm=65cm Power =2.00-0.46=1.54D at pupil | Ideal for variety of occupational needs from computers to mechanics etc. |
| Essilor Interview | Extended Focus | Monocular PD’s height, Near Rx | Top of lower lid approx 6mm below pupil centre) | 0.80D (Interview Low) 1.30D (Interview High) | Reading Add-shift E.g Add +2.00 with low shift. 2.00-0.80=1.20D at pupil | Full add 10mm below pupil.Suitable for near to intermediate screen distances. Ideal replacement for SV near. |
EYEZEN Start
Introducing two reference points in far and near vision for the lens calculation means the whole lens surface is optimised for both far and near vision to improve acuity and reduce deviation from the prescription according to object location.
Power error corresponds to a deviation from the prescribed mean sphere value. Power error either generates blur (for a positive power error) or induces accommodation effort (for a negative power error). For example, a level of power error of 0.18 D causes an acuity loss of approximately 0.05 logMAR, which corresponds to a half-line on a logMAR acuity chart (Fauquier et al., 1995).
Unwanted astigmatism corresponds to a deviation from the prescribed cylinder value and/or axis, reducing the sharpness of vision. Fauquier showed a level of unwanted astigmatism of 0.25 D causes an acuity loss of approximately 0.05 logMAR, which again corresponds to a half-line on a logMAR acuity chart.
Maintaining power error under 0.18 D and unwanted astigmatism under 0.25 D guarantees maximum visual acuity.
Effects of astigmatism and high-order aberrations of progressive-power lenses on visual acuity are always subject of research and development.
The actual power and astigmatism of a lens depend on the gaze direction, but also on the object distance. Usually when a lens is designed, it is assumed that all objects are located at infinite. In reality, they are not. That’s why the lens power and astigmatism are incorrect.
Cones of gaze directions are calculated, where power deviation is lower than 0.18 D, and astigmatism deviation is lower than 0.25 D. These threshold values are chosen because beyond them wearers will suffer an acuity loss equal or greater to one half- line on a logMAR acuity chart.
On comparison the performance factor Eyezen Start lenses to standard single vision lenses is 49% larger than standard lenses.
The prescription is considered maintained when the following is true:
• Unwanted astigmatism < 0.25 D or
• Power errors < 0.18 D
A factor of 100% means the prescription is maintained for all gaze directions in the usage zone. Eyezen Start lenses are also the only single vision lenses that take into account convergence, which happens when the wearer looks at objects at close distances. Indeed, the vergence angle increases. This is why Eyezen Start lenses are asymmetrical lenses by design.
Lens calculation now takes into consideration the gaze direction and the object distance at each point of the lens. This calculation ensures the optical power for the wearer remains unchanged from the prescription values. The wearer benefits from the same wearer power and low unwanted astigmatism in the whole lens.
| Product Features | Standard Single Vision Distance Lens | Eyezen Start Optimised Single Vision Lens (Ordered with distance vision prescription checked at the distance checking circle, monocular PD’s and fitting heights. |
| Far Vision | √ | √ |
| Near Vision | — | Prescription maintained (no boost), Enhances acuity |
| Lens Type | Spherical/Aspherical | Digitally Optimised |
| Blue Light Protection | Optional | Standard |
| Blue Light Protection Options | Smart Blue Filter and/or Crizal Prevencia | Blue UV Capture or Smart Blue Filter |
| Reducing Visual Fatigue | — | √√ |
| Better Comfort and Clarity | — | √√ |
| Better Contrast | — | √√√ |
| Age Guide | 8-40 years | 8-40 years |
In the Eyezen Start lens, a near vision point is used as a second reference point so the power of the lens is adapted to an object’s distance in near vision tasks. This near vision point is determined according to wearer’s prescription, lowering gaze direction and vergence angle. For the wearer, the mean power and astigmatism at this near vision point will be the same as the mean power and astigmatism at the far vision point. This ensures maximum acuity in far and near vision zones.The Eyezen Start lens is locally modified to provide the right prescription to the wearer according to an object’s location, no matter which part of the lens he is looking through.
Eyezen DualOptim technology, takes into consideration the gaze direction and object distance at each point of the lens. This ensures to maintain the purest wearer’s prescription throughout the whole lens. This has been verified by subjects being equipped with a helmet on which optical markers were placed,including their torsos to record trunk movements. While using a smartphone, tablet and eBook reader, data were recorded in three different postures: standing, sitting on a couch and lying on a bed. The eye declination with electronic devices(as they are held closer) is higher than when interacting with paper.
UV light passing through the lens (=Transmission) and UV reflected by the rear lens surface (=Reflection)
Clear lenses with protection factor E-SPF 25 are the highest level of protection available for everyday protection against the cumulative effects of exposure to UV rays. and means your eye is 25 times better protected than without a lens.
Reflected UV for lenses generally decreases as incidence angle increases, from an average of 28.6% (range 8.2-54.4%) at 8 deg to 20.0% (range 6.2-35.2%) at 45 deg; by comparison, non-AR lenses (scratch-coat only) reflect about 5%.
Based on reflectance and transmittance results ESPF can range in theory from 10 to 61. Changes in lens size, curvature, vertex distance, and tilt can change the amount of UV that will reach the eye, either directly or due to reflectance.
E-SPF is an index rating the overall UV protection of a lens. E-SPF was developed by Essilor International and endorsed by third party experts.
The E-SPF index relates to lens performance only and excludes direct eye exposure that depends on external factors (wearer’s morphology, frame shape, position of wear).
They offer the essential level of protection when conditions demand the wearing of tinted sun lenses (strong sunlight, altitude, beach, etc) lenses or Xperio polarizing lenses.
In today’s optical market, 56% of Australian’s require visual correction solutions.Out of those, only 5% use a prescription sun lens.
Regardless of the tint or polarised colour protection of Crizal Sun UV (up to E-SPF 50) is available and the option of a fashionable mirror coating.
“SolarFlair Sun UV” lens treatment, if being used with a tinted or polarised lens (this treatment is not able to be applied to mirror coated lenses – as the lens will come with a generic multi-coat).
Essilor Suntinted lenses
Stylistic wrap lenses
Essilor/Nikon mirror coatings and tints
There is no such thing as a scratch proof coating,rather scratch resistance is achieved by hard coating in the mould,or by spin or dip methods. TD2 is a two layer dip coating on both sides as opposed to a front side hard coat only.
Spin and dip are methods of applying hard coat varnish – spin being that the lenses are spun and the varnish is dripped onto them.
Dip coating is a much more intensive and consistent process using two different layers and different curing processes – it gives a much more even hard coat.
TD2 provides the scratch resistance almost that of glass in the airwear material as the flexibility of polycarbonate (Airwear) is very similar to the material used in the construction of the TD2 coating, hence the lens substrate and the coating flex together as the lens heats or cools, or is knocked or bumped.
Up to 50% of UV radiation penetrating the eyes is reflected off the back surface of the prescription glasses.UV from front and back surfaces is absorbed
Ensure you have the ideal drivewear and sunwear to enjoy the beautiful Sapphire coast. On a 1.5 index lens transmission of UV or blue light is not blocked by any multi-coat
Blue-Violet Light (380nm – 455nm) is important :
• Penetrates deep into the eye and is harmful
• May cause damage in retina (AMD)
While the amount of exposure to harmful blue light from these sources is that of a lower intensity than what is experienced from the sun it is important to reduce exposure from all sources of harmful blue light because the potential effects it has on your eyes are cumulative over a lifetime which is the subject of much research
Any material >1.5 index blocks UV 100% up to 380nm from being transmitted through the lens;
any index >1.6 will block a bit of blue light which is why they are a little yellow compared to 1.5 or polycarbonate
The Crizal UV coating on the back surface of the lens blocks 96% of UV that can reflect from the back surface of a spectacle lens
Prevencia coating does block 20% of the visible blue violet light by reflecting it away from the front surface.
Any material >1.5 index blocks UV 100% up to 380nm transmitted through the lens
The Crizal Prevencia has the same UV properties on the back surface as Crizal UV
On any index material Transitions blocks 100% of UV even when clear
To block reflected UV from the back surface it requires a Crizal UV coating so the back surface will block 96% of UV that can reflect from the back surface of the lens
The Transitions dyes when clear block 20% of the visible blue violet light by absorption in the lens material which is why they are a little yellow compared to 1.5 or polycarbonate
In the darkened state Transitions blocks at least 85% of blue light by absorption in the material
On a 1.5 index lens transmission of UV is not blocked by the SBF material
Any material >1.5 index blocks UV 100% up to 380nm from being transmitted through the lens
The SBF material blocks 20% of the visible blue violet light by absorption in the lens material however, they it contains a colour corrector which is why they are a little grey compared to 1.5 or polycarbonate
To block reflected UV from the back surface it requires a Crizal UV coating so the back surface will block 96% of UV that can reflect from the back surface of the lens
HOW DO COATINGS VARY ON LENSES.
Testing Scratch Resistant and AR Lenses
Abrasion resistance is actually a combination of different factors—adhesion, hardness, flexibility and impact resistance and often test can be misleading.
Bayer Abrasion: The Bayer test is one of the most often cited test methods for abrasion resistance involving abrasion from oscillating alumina zirconia sand. The ratio of haze gain of the uncoated lens to the coated lens is the Bayer Ratio.
Crizal UV forte,crizal saphire and prevencia have Bayer grades of 10, Crizal Easy 7 – same hard coating but a different Antireflection stack of layers. Poorer coatings may have rating of 1 or 2
Steel Wool Abrasion: Uses steel wool of known fiber size and quality under a specified weight for a specified number of cycles.
Adhesion: Poor adhesion results in delamination or peeling of the coating. Adhesion is measured by a Cross Hatch test. A cross hatch pattern is cut into the surface of the lens.A piece of tape of a specific grade is then pressed against these lines. The tape is quickly lifted off. This is typically repeated three times. The cross hatch is then examined for delamination.
Coating Thickness: Coating thickness is typically measured by a UV/VIS spectrophotometer to reduce risk of abrasion and delamination.
Tintability is measured by subjecting the coated lens to a tint bath and its effect .
As liquid coatings age, the viscosity and other features may change. This will result in changes to adhesion, abrasion resistance, tintability and coating thickness. Processing variables such as temperature and humidity also impact these features. It is important to have a clean and controlled process to achieve a coating with optimized optical properties and mechanical performance.
crizal type by brand |
glare |
scratch |
dust |
water |
smudge |
uv |
blue light |
sapphire |
*****^ |
*****^ |
***** |
*****^ |
*****^ |
*****^ |
n/a |
prevencia |
***** |
*****^ |
***** |
*****^ |
*****^ |
***** |
***** |
easy |
***** |
***** |
n/a |
***** |
***** |
***** |
n/a |
Crizal coatings ^ best in class
Coatings and heat
Beware of excessive heat eg the summer heat on a car dashboard, as the issue is simply down to expansion and contraction of materials so it depends on a number of factors such as the thickness of lenses, tension, and flexibility of the frame.
Bead or air blowers can even quickly destroy a lens coating.
Each pair of spectacles will be susceptible to heat just varying consequences depending on Rx, frame, temperature ranges and speed of temp change as well as repetitions of high heat change. However the rule of thumb >55 degrees coatings reform after cooling >70 the coating will likely be truly damaged.
We are exposed to harmful blue light from the sun that is more than 100 times more intense than the harmful blue light we are exposed to indoors from electronic devices and modern lighting. Exposure indoors though is likely to increase as people convert from incandescent to modern LED lighting including contained in digital devices such as tablets, mobile phones, and personal computers emitting high energy visible (HEV) light.
HEV blue light, particularly at the 450nm level that digital devices produce, penetrates to the retina. Blue light between 380 and 470nm can cause cumulative damage to the retina, cataracts, and is linked to sleep disorders.
The hormone melatonin is involved in regulating a wide range of circadian functions, including sleep. The synthesis and release of melatonin from the pineal gland are heavily influenced by light stimulation of the retina.
Computer eyestrain is the main office health-related complaint -computer vision syndrome or digital eye strain, dry eyes, eye irritation, blurred vision, and double vision.
The short wavelengths of blue light scatter easily to produce discomforting glare and reduce contrast. This has significance when using digital devices and also driving in low light conditions and at night.
Blue light unlike candlelight of yesteryear stimulates the pituitary and pineal glands which suppresses melatonin production which is required to fall asleep
Anti-Reflection Coatings tints to reduce blue light, and the lens material itself can influence the amount of blue light transmitted.
A study conducted in 2014 by the Ipsos institute on four thousand people in France, the United States, Brazil, and China revealed over one out of two people are bothered by the strong brightness of their screens. It showed the level of discomfort varies depending on the user’s age, and for younger users, the main discomfort is screen brightness.Health agencies are now taking an interest in risks related to new sources of artificial light. Cool white LEDs, in particular, present an emission peak in the harmful blue-violet band and have a more elevated luminance/brightness than traditional sources. Despite these LEDs are now present in most modern lighting systems and in a large number of screens, especially in computers, tablets, and smartphones.
Essilor has developed technologies to protect the eyes against the potential dangers of blue-violet light by at least 20% of harmful blue-violet light up to 455 nm. Furthermore, some of these technologies can be combined to further reinforce the protection against potentially harmful blue-violet light up to 35%Blue-Turquoise Light (465nm – 495nm)
• Essential light / Beneficial
• Contributes to well-being
The beneficial Blue Light however is the blue turquoise wave length between 465 and 495 nanometres on the light spectrum.
Research shows that exposure to this light plays an important role in regulation of the circadian rhythm (sleep-wake cycle ) by stimulating melanopsin-containing retinal ganglion cells
Blue light protection ( harmful blue versus beneficial blue)
The blue violet light between 415 to 455 nanometres on the light spectrum is believed most toxic to retinal cells and for long-term vision issues such as age related macular degeneration^
^Transmission of light to the aging human retina: possible implications for age related macular degeneration Experimental Eye Research, 79(6), 753-759, 2004
The blue light hazard and the sleep / wake cycle.
The most popular clear spectacle lens materials do not completely block the most plentiful source of UVR – the solar spectrum between 350 and 400nm.
Blue light filters benefit users for screens due to the improvement in contrast. There is a need for a large well controlled study encompassing and controlling for more factors in for symptomatic and asymptomatic patients. Anti reflection coating will ensure visual comfort for screen users as it will cut down on internal reflections and back surface reflections from the spectacle lens and so reduce distracting and discomforting glare. Quality of coatings can vary markedly.Blue wavelengths are the shortest in the visible light spectrum and most likely to scatter. Blue light may interfere with the body’s circadian rhythm, so that blue light exposure in the evening may interfere with the ability to sleep.
More research is needed as to how much blue light would need to be removed to reduce any symptoms. More people are now aware of the need for blue light protection glasses despite their limitations due to natural abundance of sunlight. Examples of company awareness of the issue are attested by developments such as GE Align,Apple Night shift,Phillips Hue,Microsoft Night light, Samsung Galaxy Blue light filter and software such as F-lux which reduces the artificial blue light fro the screen.
Like all visible light, blue-turquoise light helps you perceive colours and shapes. Blue-turquoise light helps regulate your everyday sleep cycle
Still need to avoid reflections so Crizal Sapphire UV ESPF 35 is best-in class UV protection, approved by Cancer Council and is recommended.
The latest Sapphire optical lens coating comes with an E-SPF rating of 35 and 25% reduction of those troublesome off centre reflections.
The ‘sapphire colour’ minimal bloom reflects away wavelengths that are the least sensitive for good vision, unlike eg a commonly found green residual bloom on some lens coatings. Excessive light leads to a world full of reflections for spectacles wearers – Back and front surface reflections,optical diffusion and ghost images.
There are two ways to cut blue-violet light: via the substrate or via a Smart Blue filter coating.
Crizal Sapphire UV is not a blue cut coating but it can be combined with embedded blue cut filter or Transitions lens technology
- The blue hazard is from 400 – 455nm; is virtually all from sunlight, there is some question over high output industrial LED lighting but it is still very small compared to sunlight; and is specific for the at risk group of patients – those with a direct family history of AMD, smokers; those who are obese or have poor nutrition; people taking photosensitising medications and those who spend their working life outdoors. These people are at risk from the oxidation processes in the outer retina that have been well documented by many researchers. Crizal Prevencia and SBF both block 20% of the light from 400 – 455nm which in the lab reduces RPE death by 25%. Combining the two together increases filtering to 35% with a corresponding reduction in cell death in lab experiments.
- the sleep / wake cycle – melanopsin is active from 465 – 495nm; blue filters can’t increase the amount of these wavelengths arriving at the retina but they shouldn’t block them as in the case of Gunnar blue blocking lenses.
Crizal Prevencia lenses
Reduces the rate of retinal cell death by 25% due to to the blue-violet light filtering and thereby reducing cumulative risk of AMD , but let’s the essential blue-turquoise and visible light to pass through.
Such selective filtering by crizal prevencia coatings ensures your eyeglasses guide you safely and clearly even in the simplest of single vision lenses. Often advertising claims can confuse eye problems or medical conditions that are requiring attention so we can help with more information.
Vision problems can exist even with sharp vision eg doubling or ghosting which is why lenses that suit your age and your vision are needed together with scheduled eye exams for complete eye care
Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood —can be most disruptive at night which can upset your internal clock that aligns with the environment. Crizal Prevencia is the recommended coating as a protection as it filters out harmful Blue-Violet light.
For protecting against blue light due to family history of medical conditions or advanced eye diseases such as AMD or other risk factors where transitions lenses are declined combining SBF (smart blue filter) and Prevencia allows maximum blue cut in a clear lens that would be worn outdoors by 30%.
So clear lenses also can protect your vision by protecting your eyes and the coating particularly in these cases is intended to constitute medical benefits.
The optometrist vision tests you can expect for complicated or common eye conditions, eye diseases and vision symptoms that occur at different stages of life will serve to reduce your problems that can occur.Glasses or contact lenses may offer special vision protection
Essilor launched in 2013 Crizal Prevencia, in 2016 the smart blue filter and in 2018 widened harmful blue light protection as a specific category in its portfolio of lenses following on from other major cagegory breakthroughs.
Essilor invented the progressive lens category in the 1950’s to correct vision across a visual zone from near to far,beyond the restrictive arm length.
As a world leader in prescription lenses continuous refinements followed.
In 1993 the anti-reflective category of clear and more scratch resistant lenses were developed and all continously improved through R+D.
Percentage of harmful blue violet protection
| Value | |
| Standard lens | 5% |
| Essential Blue Series SBF | 20% |
| Essential Blue Series SBF with Crizal Prevencia | 30% |
| Transitions 7 unactivated | 20% |
| Transitions 7 activated | 85% |
| Transitions Xactive unactivated | 35% |
| Transitions X active activated | 88% |
UV transmission via the lens front surface is cut purely by the nature of the material
UV Cut: Front surface with or without Crizal UV or Crizal Sapphire UV or Crizal Prevencia
all indices > 1.50 = 100% UV cut at 400nm
Transitions all indices = 100% UV cut at 400nm
1.50 = 96% cut at 400nm
Reflected UV via the lens back surface is cut purely by anti reflection coatings
UV Cut: back surface reflected UV without Crizal UV or Crizal Sapphire UV or Crizal Prevencia
all indices / all materials = 0% UV cut at 400nm
UV Cut: back surface reflected UV with Crizal UV or Crizal Prevencia
all indices / all materials = 96% UV cut at 400nm
with Crizal Sapphire UV = 98% UV cut at 400nm
Crizal UV (also known as Crizal Forte UV) – has no blue blocking effect
The front surface – transmits 99.2% of light with a residual bloom in the yellow green range.
Any UV filtering via the front surface of the lens is solely dependent on the monomer of the base lens e.g. CR 39 only takes out 94% of UV while all of the indices above that take out 100% of the UV.
The back surface – blocks 96% of the UV reflected by the back surface of the lens with an incident angle of 135 degrees.
Crizal Sun UV (applied to the back surface of sunlenses ) in this case no multicoat layers on the front.
Re front surface – any UV filtering via the front surface of the lens is solely dependent on the monomer of the base lens e.g. CR 39 only takes out 94% of UV while all of the indices above that take out 100% of the uV
The back surface – blocks 98% of the UV reflected by the back surface of the lens with an incident angle of 135 degrees
Crizal Prevencia: front surface selectively reflects away 20% of the wavelengths between 400 and 455nm with a peak at 435nm, it allows through at least 98% of the wavelengths around 470 – 490nm in the range of the melanopsin receptors
The back surface – as for Crizal UV – the back surface blocks 96% of the UV reflected by the back surface of the lens with an incident angle of 135 degrees
Nikon Seecoat Blue UV The front surface reflects away 5% of the wavelengths between 400 and 500nm with a peak of 10% at 455nm .
Back surface -as for Crizal UV – blocks 96% of the UV reflected by the back surface of the lens with an incident angle of 135 degrees.
Blue Cut: Materials
Smart Blue Filter all indices = 20% between 400 & 500nm
Transitions Grey, Brown and Graphite Green – clear state indoors = 20% between 400 & 500nm
Transitions Grey, Brown and Graphite Green – dark state outdoors = min 85% between 400 & 500nm
All other materials regardless of index = minimum blue cut so technically = 0% between 400 & 500nm
Blue Cut Coating:
Crizal Prevencia = 20% between 400 & 500nm
No other Essilor coating cuts blue
Blue cut combining blue cut material and coating:
Smart Blue Filter all indices + Crizal Prevencia = 30% between 400 & 500nm
Transitions Grey, Brown and Graphite Green – clear state indoors = 30% between 400 & 500nm
Transitions Grey, Brown and Graphite Green – dark state outdoors = unchanged at min 85% between 400 & 500nm
Essilor and Nikon HMC (hard-multicoat) processes don’t use a spin coating. The testing regimes for establishing scratch resistance include.
– Tumble test – the lens is physically rolled around in a barrel with stones and abrasive materials of particular sizes.
– Bayer test is for abrasion and is done with sandy grit again of a particular size and the lens is shaken backward and forwards in a tray of this grit.
– 100 Blows test – an erasure, on the end of a 1kg weight, is wrapped in cotton fabric and moistened with alcohol, it is then rubbed backward and forwards 100 times across the surface of the lens.
– Crosshatch test – for adhesion – five razor blades mounted side by side – is used to make a cross-hatch pattern of 1mm squares on the surface of the lens and then powerful gaffer tape is applied and then ripped off in an attempt to take with it chunks of the coating.
Most manufacturers use a few of these tests or variations of them to verify their hard & HMC coatings – tintable coatings are less resistant. When coated most materials end up with similar scratch resistance.
Returns on HC and HMC lenses low if properly maintained but quality can vary markedly. The vacuum process applies the following layers:
Front surface: bonding layer,anti-reflection layers,topcoat – easy clean layer,the non-slip layer for edging (removable)
Back surface: bonding layer,UV cut layer anti-static,anti-reflection layers,topcoat,easy clean layer,the non-slip layer for edging (removable)
Transmission of UV is blocked by the material and reflection from the back is blocked by Crizal UV or Prevencia
Blue light can be blocked by reflection at the front surface or in the material by absorption for Transitions and SBF.
Physical vapor deposition (PVD) describes a variety of vacuum deposition methods which can be used to produce thin films and coatings often in multicoats of compounds such as silicon dioxide,zirconium dioxide,aluminium oxide in a number of layers where the refractive index and the thickness of each layer can be carefully controlled.
Scratch resistant coatings are thicker than the multicoats and can be a dip or spun process.In a normal lens, about 4 per cent of the light is reflected as it passes through each side of the lens. This means that approximately only 92 per cent of the light reaches the eye. Both ghosting from the front and flare from the back affect the quality of the image that you see.
Anti-reflective coating improves the light transmission through the lens to nearly 99 per cent and therefore can reduce the effects of ghost and flare substantially.
Call to discuss digital eye strain solutions to alleviate postural and eye strain symptoms.
We are more connected digitally than ever before and more dependent on digital screens. More people are presenting with digital eye strain symptoms.
Blurring of vision can be caused by many different ailments or eye defects,to natural deficiencies, illnesses, pre existing medical conditions.
We recognize poor quality lenses and coatings due to poor quality control in manufacture can sometimes be a cause.
Optometrical and medical peak bodies recommend children to those of advanced age seek comprehensive eye care.
Eye problems can occur not only from a vision problem but from a medical condition requiring attention.
No matter the type of vision problem or medical problem or medical condition please consult a qualified professional even if you suspect its due to natural deficiencies.
Our advice and products goes beyond expert tips on how to choose lenses for your eyeglasses to ensure the limitations are not only due to natural deficiencies ( eg as you find out how your age impacts your vision during your life ) but also to what may constitute medical advice for childhood conditions or advanced age related conditions. Rather than internet browsing about eye problems or a possible medical condition requiring attention please for more specific information visit us at Bega or book appointment here.