Lens Materials, Tints and Coatings - Student Slides 2024 PDF

OPT505: Clinical Skills and Refractive Management: Lens Materials, Tints and Coatings Claire Wright One Time Code UR-JH-LR  Welcome to the Dispensing part of OPT 505 This part of the module consists of: 6 Lectures 6 Labs – 2 hours each 2 x Formative OSCE’...

OPT505: Clinical Skills and Refractive Management: Lens Materials, Tints and Coatings Claire Wright One Time Code UR-JH-LR  Welcome to the Dispensing part of OPT 505 This part of the module consists of: 6 Lectures 6 Labs – 2 hours each 2 x Formative OSCE’s 1 x Final OSCE weighted at 15% of the Modules mark UR-JH-LR  Welcome to the Dispensing part of OPT 505 1 x Final OSCE weighted at 15% of the Modules mark 1 x Written Dispensing Scenario 1 x Focimetry of Bifocals Both part 20 minutes UR-JH-LR Core competency 4.1.1 Ability to advise on, order and to dispense the most suitable form of optical correction taking into account durability, comfort, cosmetic appearance, age and lifestyle UR-JH-LR Aims of today You should be able to: Explain the properties of different lens materials Compare advantages and disadvantages of the various materials available Discuss the properties associated with an ‘ideal lens’ List the potential undesirable optical or cosmetic effects that can result in the unsuitable choice of lens material Describe different tinting processes Explain the advantages and disadvantages of different tints available List the regulations/laws regarding tints/coatings Discuss additional lens coatings and their uses UR-JH-LR The Ideal Lens Patients Concerns Our Concerns Looks good Lightweight Stable material Aberration free Scratch Reflection free Thin Good vision resistant Abrasion & impact Easily tinted, UV Minimal resistant protection Low cost? glare Available in a range Able to retain a of surface hard and reflection- processes free coat easily Lens Properties Relative Density/ Thickness Index curvature Weight UV Reflectance Abbe No. Aberrations transmission/ absorption Strength/ Impact Durability Tintability Hardness Resistance Processing Ease of Capability Manufacture Key Terms Refractive Index (RI): the ratio of the velocity of light of a given frequency in air to the velocity of the same frequency in the refracting medium V-Value: (also known as the Abbe Number) the measure of the materials dispersion – tells us the optical quality of material. Higher the dispersion (TCA) the lower the Abbe number (a bad thing optically) Relative Curvature: used to indicate the degree of flattening achieved by the use of a higher RI material Lens Materials CR39 Crown glass Trivex Plastic Glass Mid & High Index Polycarbonate glass Tribrid Flint glass* Mid & High Index plastic Classification of Materials Refractive Index Normal Index 1.48 < 1.54 Mid Index 1.54 < 1.64 High Index 1.64 < 1.74 Very High Index 1.74 and above Lens Materials and Properties Product Refractive Index (ne) Abbe number Density (Ve) (g/cm3) Plastic (Hoya) CR39 1.50 58 1.32 PNX (Trivex ) 1.53 43 1.11 Polycarbonate 1.59 31 1.20 Eyas 1.60 42 1.32 Eynoa 1.67 31 1.37 Eyvia 1.74 33 1.46 Glass (Std) 1.5 (crown) 1.523 59 2.54 1.6 1.600 42 2.54 1.7 1.701 39 2.99 1.8 1.802 35 3.47 1.9 1.885 31 3.99 Aspheric Form Aspheric form as an alternative Advantages Disadvantages Thin More distortion than equivalent steep lens Flatter Sensitive to decentration Lighter than an equivalent standard lens Better off-axis vision Less oblique astigmatism Less distortion than an equivalent flat lens Less spectacle magnification Remember: Estimating Refractive Index using Relative Curvature F=n–1 Rc = 1.523 – 1 Rc = FLM r nnew mat – 1 Ffoci When comparing the new lens with Crown Glass n = 1.523 or CR39 n = 1.498 Relative Curvature % thickness Refractive Index Curve variation factor reduction 1.5 1.00 0% 1.6 0.85 15% 1.7 0.75 25% 1.8 0.65 35% 1.9 0.58 42% Choosing which Lens Material The decision on lens materials includes: 1. Plastic vs. Glass 2. Index 3. Lens form 4. Durability Choosing the best lens for Vision Lens materials that produce the best vision Spherical Highest Abbe number Lower refractive index CR39 (Plastic: n = 1.5, V= 59, Spherical) Crown Glass (n = 1.523, v = 59, spherical) Advantages Disadvantages Low distortions Heavy- if Glass Hard surface Easy to break/shatter Highest Abbe no. Thick in high prescriptions Easy to manufacture Common vision problems caused by lens materials – off axis performance Monochromatic aberrations - Oblique Astigmatism - Distortion Warping of the peripheral field of vision Transverse Chromatic Aberration (TCA) - Off axis dispersion of white light into the colour components Dealing with Oblique Astigmatism Making the lens steeper or using a best form lens will reduce/eliminate oblique astigmatism Best form: Point Focal BUT – a steeper lens (and point focal) will be thicker and produce more magnification Aspherics can eliminate oblique astigmatism (more on this later) Best Form Lens “A lens designed to minimise the effects of certain stated defects or aberrations in its image forming properties” Dealing with Distortion Reduce the BVD Use a small lens/frame Use a best form lens e.g. point focal *NB: aspheric lenses will create more distortions than equivalent steep lens but less than equivalent flat lens Transverse Chromatic Aberration (TCA) Otherwise described as Dispersion -Only occurs off axis Visible (white) light is dispersed into it’s components (colours) due to the slight difference in wavelengths- causes a rainbow effect. ( - think of window charms) The further from optical centre, the more dispersion that can occur TCA can be calculated using the two following formulae and is measured in Prism Dioptres P = Prismatic effect TCA= P V = nd - 1 V = V value V nf - nc TCA: Tolerance It is generally accepted that most people will only notice TCA above 0.1 Generally, it affects higher Rx’s (especially Myopes) It causes - poor off axis vision - colour fringing - poor vision in low contrast lighting - poor near vision with some PPLs TCA in different Rx V60 V40 V30 -4.00 0.09 0.13 0.17 -6.00 0.13 0.19 0.26 -8.00 0.18 0.26 0.35 -10.00 0.22 0.33 0.44 -12.00 0.27 0.41 0.54 Dealing with TCA To reduce TCA : - use a lens with as high V value (Abbe number) as possible- may increase thickness - good centration of lens - small vertex distance - adjust pantoscopic tilt - choose a smaller frame High Index: Density and Reflectance Density - increase in density increases the weight of the lens - higher index lenses are generally denser (not always) Reflectance - increases with increasing Index TCA - increases with Rx, Lens Size and Index So which one? What we Side effects want Does the perfect lens exist? Appearance Distortion No! Vision Reflections So…we have to make a compromise Comfort TCA The Compromise (with high index lenses) Density - high index lenses are thinner (less volume) so may not be much heavier - many are willing to compromise on this for good cosmesis - in a small frame, it is less of a problem - plastic is still significantly lighter than glass! Reflectance - Increasing the Refractive Index increases Reflectance - MAR coats can reduce this problem (most high index come with this as standard) TCA - Many people can adapt to TCA and learn to ignore - Given the choice, they prefer a thinner lens Choosing the Best Lens for Cost The lens material that will be cheapest for the patient will be: - easy to manufacture - available in a range of forms and powers - readily available Example: Px wants near vision specs and multiple pairs CR39 (1.5 Plastic) Advantages Disadvantages High abbe no (59) Easily scratched Shatter resistant Thick in high prescriptions Light Easy to manufacture Choosing the Best Lens for Thickness To reduce the thickness of a lens there are a few options including: - higher refractive index - flatter form - aspheric form High Index/Aspherics Advantages Disadvantages Thin Lower Abbe no. Lighter (unless glass) TCA’s Increased reflectance Choosing the Best Lens for UV Protection To provide best protection from damaging UV ray the lens must: - block 100% of UVA and UVB light - This is often described by the ‘UV cut off value’ = Trivex Advantages Disadvantages High UV cut off (400nm) Lower index (1.53) Strong Thick in high prescriptions Moderate Abbe no. (41) Light Choosing the Best Lens for Protection To provide the best overall protection for the eyes, the lens must: - be strong - perform well on the Gardner impact test - be resistant to chemicals Trivex or Polycarbonate Trivex Polycarbonate UV cut off 400nm UV cut off 380nm Strong (Impact Resistant) Bullet-proof (strongest) Moderate Abbe no (41) Low Abbe no (31) 1.11 g/cm3 1.20 g/cm3 Index 1.53 Index 1.59 Resistant to chemicals Opacifies with chemicals Choosing the Best Lens for Comfort For the best comfort, the best lens choice needs to be - lightweight - unreactive (all modern materials fulfil this) Trivex or Hi-Index Trivex Advantages Disadvantages of Both Hi-Index Advantages High UV cut off (400nm) Lower index (Trivex 1.53) Thinner Strong Thicker lenses (Trivex) Lighter Moderate abbe no. (41) Reduced Abbe no (Hi-Index) Different thickness reduction Light Strong *Low density in some materials also comes with a low Abbe no. e.g. polycarbonate We need to be able to advise on the most suitable solutions, along with the advantages and disadvantages of each choice  Prescription Analysis What lenses would you suggest for this Patient? High Index – 1.74 plastic with MAR coating What would you warn the about? TCA, Distortion, Increased reflectance –covered by MAR Prescription Analysis What lenses are best for impact resistance? Trivex or Polycarbonate Summary No such thing as the ‘ideal lens’ We need to compromise between vision, weight and/or thickness Lens design, frame selection and centration are key Work with your patient to find the ‘ideal lens’ for them 4.1.1 Ability to advise on, order and to dispense the moist suitable form of optical correction taking into account durability, comfort, cosmetic appearance, age and lifestyle Tint & Coating Properties Application UV status Conditions Rx Pros Cons considerations The science Suitability behind it  Tinting and Coating Lenses The light absorbency or light blocking, hardness or reflectance of lens types can vary To alter or improve the lens design, coatings and tints can be added Uncoated lens (reflections) Coated lens (no reflections) Tinted lens (increased absorbency) Tints Tints can be added for a number of reasons: 1. Reduction of glare/ increased contrast across the visible spectrum 2. Protect against harmful radiation 3. Cosmetic appearance 4. Treatment for dyslexia and other learning difficulties Solar Radiation and Electromagnetic Spectrum  Solar Radiation and Electromagnetic Spectrum The optical range of solar radiation is 100 to 10,000,00nm Visible light runs from around 380 to 780nm Our eye is most sensitive to 555nm (yellow – green) As an Optometrist, we are concerned about the high energy end of the spectrum – Blue/UV light UV Radiation UV radiation is the high energy end of the spectrum Its range is from 10-380nm It is split into three zones or categories - UVA: 315 – 380nm - UVB: 280 – 315nm - UVC: 10 – 280nm  Longer wavelength penetrates further into the skin and ocular surface  Shorter wavelength can be more damaging as it has more energy UVA (315 – 400nm) Not absorbed by the ozone layer UVA travels furthest into the eye and can cause damage to both the crystalline lens and the retina There are some links to UV damage and cataracts and AMD Behar-Cohen, F., Baillet, G., de Ayguavives, T., Garcia, P. O., Krutmann, J., Peña-García, P., Reme, C. and Wolffsohn, J. S. (2014). "Ultraviolet damage to the eye revisited: eye-sun protection factor (E-SPF®), a new ultraviolet protection label for eyewear." Clinical Ophthalmology (Auckland, N.Z.)8: 87-104. UVB (280 – 315nm) UVB is responsible for sunburn and most skin cancer - it can directly alter DNA Most of UVB is absorbed by the cornea UVB UVA Some radiation (above 295nm) can reach the retina Skin UVC (10 – 280nm) This range of UV light is absorbed by the ozone layer and the atmosphere This is the most active and toxic end of the spectrum When required it can be artificially created - e.g. by mercury or germicidal lamps UV cut off in Lens Materials Lens material specifications include the UV cut off This is the approximate level of solar radiation that is blocked by the material Material Approx. UV cut off CR39 – 1.5 350nm Polycarbonate – 1.59 380nm Trivex 400nm 1.6 395nm 1.67 395nm 1.74 395nm UV Blocking Treatments (Clear) In order to increase the UV protection of a lens, clear treatments can be used applied - e.g. UV400 coating – available everywhere Coatings that protect from a higher level of radiation can result in a yellow or orange colour as short wavelengths in the visible spectrum will be blocked too - e.g. Medical tints Visible Light Visible light is essential for vision Reflected light is particularly problematic An excess of light can cause discomfort = Glare Glare can be due to light being too bright or concentrated  Glare Distracting/Veiling Glare Discomfort Glare Disability Glare Blinding Glare Reduced by clear or Reduced by photochromic Reduced by photochromic, Reduced by polarisation photochromic lenes with or tinted lenses polarised or tinted lenses MAR coat Reducing Visible Light Transmission Tinted Lens – A generally absorptive lens that has a noticeable colour in transmission There are various coatings and tint options available to block out visible light: 1. Tinted lenses - manufactured or coated 2. Photochromic lenses 3. Polarised lenses Tints – Absorption and Transmittance Absorption (Abs): - the more light a lens absorbs, the darker it looks - Described as a % Luminance Transmittance (LT) - the more light a lens allows through, the lighter it is - Described as a % Tints – Absorption and Transmittance Lens tints can be described by either: - Abs = 20% or LT = 80% This is calculated ignoring reflections Spectral Transmittance Spectral Transmittance Factor (STF): The fraction of the original incident light transmitted by the lens for a particular wavelength This is expressed as a decimal or % If STF is plotted for a series of wavelengths (e.g. 300 - 1000nm) then a curve can be produced Most curves are plotted for a 2mm thick lens A spectraphometer can be used to measure this Spectral Transmittance STF plot of the Transmittance Curve Luminance Transmittance Luminance transmission factor (LTF): an overall effect of a filter (tint) on a standard eye viewing a standard light source Standard light source – daylight A single figure for each tint type LTF Transmission Photopic conditions A 100-80% Only in reference to visible light spectrum AB 80-58% B1 58-43% B2 43.2 – 29.1% C 29.1 – 17.8% D 17.8 – 8% Rules and Regulations for use of Tints* BS EN ISO 12312 – 1(2013) Eye and face protection – Sunglasses and related eyewear: Part 1 – Sunglasses for general use BS EN ISO 8980-3 (2013) Ophthalmic optics – Spectacle lenses – Uncut finished spectacle lenses: Part 3 – transmittance specifications and test methods Rule 94 of Highway Code: At night or in poor visibility, do not use tinted glasses, lenses or visors if they restrict your vision *Full list includes: BS EN 169, BS EN 170, BS EN 171, BS EN 174, BS EN 207, BS EN 379, BS EN 1836, BS 7394 (Pt2), BS EN ISO 13666, BS EN ISO 14889 Sun Glare Classification BS EN 1836 : 1997 (*Absorbed by the BS EN ISO 12312 – 1 (2013)) Transmittance LTF % Description Usage Restrictions Filter Category Clear or very light Comfort, indoors, None 100-81 0 tint cosmetic Light Low sunlight Not suitable for night 80-44 1 driving Medium tint Medium sunlight Not suitable for night 43-19 driving 2 Dark tint Bright sunlight Not suitable for night driving, may not be 18-9 3 suitable for any driving Very dark tint Very bright sunlight Not suitable for any 8-3 driving 4 Types of Tints (Filters) Photo Solid chromic Glass Plastic Photo Dip- Coated Solid chromic dyed Glass - Solid Tint The tint is uniformly distributed through the material at the point of manufacture - this results in an uneven colour in higher powers Colour of the tint affects the transmission Old NHS tints were solid Gives Panda Eyes and light patches on skin in higher minus prescription as more tint absorbed in the thicker part of the lens Glass - Solid Tint Colour indicates transmission properties: - Pink/Brown absorbs UV - Green absorbs UV and IR - Grey absorbs UV and gives less colour distortions - Amethyst absorbs yellow and improves contrast - Yellow absorbs blue and improves contrast in hazy conditions Rayban G15 is an example - IR & heat absorbing G15 tint The name refers to a tint specific to Rayban® Developed in the 1950s for pilots Solid tint Abs 85%, LT 15% Green colour offers less colour degradation (more natural) - as optimises vision for 555nm Ferrous oxide used to help colour with IR absorption - useful for tropic climates Glass – Coated tint Reflecting filters will reflect unwanted light Coating is applied in a vacuum to the surface of the lens Even appearance (equi-tint) - edges are clear - can be scratched off Lots of colours available Colour does NOT indicate transmission properties of the lens Glass - Photochromic Darkens and lightens according to levels of ambient UV Activated by silver halide crystals that decompose on exposure to UV light and produces a tint, then reverses as UV removed Classified as a solid tint May hear patients refer to them as Reactolite, Adaptive or Photobrown Extra – these are brands Glass - Photochromic Performance is affected by: - Temperature (better in cold climates than hot) - Type of radiation - Thickness of lens material - Age of lenses - Amount of light Plastic – Solid Tint Casting material is dyed Tint can appear uneven - especially in higher powers Absorbs unwanted light Use for specialist tints E.g. for particular sports etc. Plastic – Dip-dyed A finished (but not coated) lens immersed into photographic dry at 95oC Tint permeates surface (up to 1mm) Even appearance Absorbs unwanted light Colour does not indicate STF/transmission properties Not always successful on lenses other than CR39 Available in lots of colours and gradients Plastic - Photochromic Spiro-oxazines or spiro-pyrans and fulgides added to CR39 lens material Exposure to UV causes a portion of each molecule to rotate Radiation is absorbed in this process Removal of exciters (UV) causes molecules to flip back to original orientation 100% UVA/B protection Plastic - Photochromic Transition® (Essilor) (multiple colours and generations available) Equitint https://www.transitions.com/en-us/why-transitions/the- technology/photochromic-tech/ Sunsensors (Kodak) Solid tint Suntech (Hoya) Spin coating Drivewear (Young Optical) Combination of polarised and transition lenses Plastic - Photochromic https://www.transitions.com/en-us/why-transitions/the-technology/photochromic-tech/  Polaroid at all times Photochromic – reacting to visible light Drivewear Darkens to full depth behind windscreen Available in Rx Not suitable for driving at night! Transitions® Xtra Active Manufactured the same way as Transitions Designed to be darker outdoors 10% LT is the darkest available even at high temperatures Darkens behind a car windscreen between 18-43% LT (not as effective as Drive Wear) Pale tint indoors 83% LT 100% UV protection Also available in specialist sports goggles/visors and lenses Polarising Lenses Polarising lenses are designed to reduce the visual effects reflected from a horizontal surface - wet road, snow, water The polarising effect is most profound when viewing at or near Brewster’s Angle Excellent colour definition and contrast 99% UV absorption from 380nm (to meet CE regulations) Reduction reflected light transmission can decrease glare problems Polarised light – Brewster’s angle Brewster’s angle: the angle at which complete polarisation of light occurs. The reflected and refracted rays of light at 90o from one another Derived from Snell’s law: θ= tan-1 n2/n1 Light that reflects off a horizontal surface is partially polarised - Most of the light vibrates along the horizontal plane Plastic – Polarised Light The largely horizontal vibrations create glare The vertical vibrating light is useful A polarised filter, blocks the horizontal vibrating light only Plastic - Laminated A different method to tinting a lens A plastic sandwich of clear and tinted lens material - Chemically bonded together Polarised lenses are formed this way Even tint - Unaffected by prescription Coloured plastic Coloured plastic lens (0.8mm) UV 400 (0.8mm) Vacuum Coating Equi-tint Mirror finishes available Anti-reflective coatings are vacuum coated Variety of colours and semi mirrored finishes available Coatings Hard coat (scratch- Hydrophobic resistance) Anti-reflection Multipurpose Hardcoat Plastic lenses are all relatively soft and easily scratched The ‘hardcoat’ is added to toughen the surface Normally applied by dip coating or spin casting There are a myriad of different types available with little standardisation - varies with manufacture - materials such as quartz are used Anti-reflection Coatings Vacuum coated Works on destructive interference Double layer coatings more effective than single coatings Works better with a hard coat Can have additional layers hydrophobic, easy clean, smudge resistance and dust proof THIS IS NOT AN ANTI-GLARE COATING Anti-reflection Coatings When light travels through a refractive material such as a spectacle lenses, a % is lost at each surface to reflection - for normal incidence, in CR39 it is 4% per surface - for normal incidence, in 1.9 glass it is 9% per surface In order for the anti-reflection coating to work, two conditions must be met: The path condition The amplitude condition Uncoated Coated Anti-reflection: destructive interference The Path condition: - two reflected waves of light, one half wavelength apart will cancel each other out - therefore if the anti-reflection coating is ƛ/4 thick then the reflected light is cancelled out - a coating of set thickness is used to alter the path of the reflected light at each surface (a multiple of ¼ wavelength) Anti-reflection Coating Effectivity If both the path and amplitude conditions were met, it would be 100% effective against a specific wavelength of light However, there is a limited range of useful coatings available with limited range in index - CR39 would require n = 1.22 - Crown glass would require n = 1.23 Most use magnesium fluoride n = 1.38 (perfect for 1.9 glass) There will also be variation across the visible spectrum as the wavelengths change Dual Layer AR coatings If more than one coating of ƛ/4 thickness is used of different refractive index the effectivity can be increased e.g. n1 = 1.38 and n2 = 1.70 n1 = 1.38 n2 = 1.70 nlens = 1.49 Multi-layer Anti-reflective (MAR) Coatings Many lenses are now available with MAR coatings that consist of multiple layers of anti-reflection coatings Multiple layers can be used to reduce the reflections across multiple wavelengths They also include many of the following: - Hard coat - Hydrophobic - Oleophobic coating - Adhesive layers - Anti-smudge - Dust-protection Hydrophobic Coating The way water spreads over a lens surface is determined by the wetting angle Wetting angle: the tangent to the edge of the water droplet makes with the surface The larger the wetting angle, the better the hydrophobic properties - a low wetting angle results in the droplet spreading across the surface - a high wetting angle results in the droplet running off the surface as a droplet Specialist Tints & Coatings There are many other specialist tints and coatings available: Cerium Colourimetry Tints - Irlen Syndrome, Visual stress, Migraine Vistamesh/Honeycomb - Visual stress, Occupational, Medical requirements Blue Blocker - Smart phones, tablets, monitors, daylight; reduces blue light by 35% 380- 450nm The evidence for each of these types is conflicting Blue Light Blue light starts and ultra violet ends at 400nm Numbers vary depending on the literature Can 401nm be less harmful than 399nm? Blue emitted by Sun, T.V’s, Computer Screens, Tablets and Smartphones A current popular coating is the blue blocker treatment* *the evidence for this has recently been refuted and there is no definitive proof of this effect O'Hagan, J. B., Khazova, M. and Price, L. L. (2016). "Low-energy light bulbs, computers, tablets and the blue light hazard." Eye (Lond)30(2): 230-233. https://www.abdo.org.uk/regulation-and-policy/advice-and-guidelines/updates/c9-3-1-blue-light-guidance-for-abdo-members/ Identifying Lenses There may be situations where you need to identify an unknown lens, either to replicate it for an order or to identify a likely issue with an unknown pair of spectacles This guide will cover basic methods used to identify different lens properties when examining an unknown lens. This guide will cover: - Single vision and multifocal lenses - Coatings and tints Key characteristics SV or Material Power Cut/uncut Multifocal Edge R or L Tints Coatings finish Material - Glass or Plastic? The main thing to determine, is if the lens is glass or plastic. 1. Feel the temperature – glass tends to feel cold when first picked up, plastic tends to be at room temperature 2. Drop the lens on to a solid surface (from a short height) and listen to the sound – a higher pitched sound indicates glass 3. Tap the surface with metal jewellery, glass watch face or a stone e.g. from a ring – glass will have a higher pitched tap than plastic Cut or uncut? State whether this lens has been cut for a frame or not An uncut lens is called a blank and will be cut for a frame A cut lens has been glazed for a specific frame Uncut/blanks Cut lenses R or L lens Determine whether the lens was glazed for a R or L eye of the frame Look for the side that is shaped for the nose Right Left Power – Negative or Positive? (Hand neutralisation ) Determine if it is a positive or negative lens 1. Magnification or Minification 2. Shape of the lens 3. With or against movement when looking through lens Positive lens Negative lens Power - Astigmatic? Look to see if the lens has a simple spherical prescription or an astigmatic prescription Rotate the lens while looking at a straight line or cross – look for scissoring Astigmatic Look at the scissoring or misalignment of a cross or straight line when rotating the lens Spherical If the lines do not distort or rotate, then the power is equal around the point of rotation and it is spherical Single Vision or Multifocal? Identify lenses as single vision or multifocals (bifocals or progressive power lenses – PPLs) Look at the change in power – usually increase in magnification for reading Look for segments Tints or Coatings Look to see if any tints or coating have been added to the lens Put the lens on a blank white surface to look for tints or colours Use the reflections from the lighting above to look for coatings, coatings will alter the colour of the reflections seen on the lens Tint Anti-reflection coating No tint or coating Edge finish If the lens has been glazed – how have the edges been finished? What type of frame is it destined for? Smooth finish Bevel Mini-Bevel Groove (supra) (Rimless Mount) (Full Frame) Resources Association of British Dispensing Opticians www.abdo.org.uk A.B.D.O. College www.abdocollege.org.uk BlueBocker http://www.essilorpro.co.uk/SiteCollectionDocuments/Crizal%20Prevencia_Simplified%2 08pp%20(1).pdf Corning - SunSensors www.corning.com Drivewear® Lenses www.drivewearlens.com European Hard Resin Institute www.hardresin.com Federation of Manufacturing Opticians www.fmo.co.uk Spectacles by Glyn Walsh (pg. 85 -101) –see moodle Transitions http://www.transitions.com/en-gb/ The Norville Group Limited www.norville.co.uk Worshipful Company of Spectacle Makers www.spectaclemakers.com Younger - Transitions® - NuPolar® www.youngeroptics.com