69654 EXE MODULE 3_v3

LENS INDICES, COATINGS, DESIGNS, TINTS. KMFL TRAINING ACADEMY

“I formerly had two pair of spectacles, which I shifted occasionally, as in travelling I sometimes read, and often wanted to regard the prospects. Finding this change troublesome, and not always sufficiently ready, I had the glasses cut, and half of each kind associated in the same circle. … By this means, as I wear my spectacles constantly, I have only to move my eyes up or down, as I want to see distinctly far or near, the proper glasses being always ready.” Benjamin Franklin In this Module 1.  Lens Indices 2.  Plus and Minus Lenses 3.  Aspheric Lenses 4.  Lenses for Kids 5.  Lens Coatings 6.  Lens Designs 7.  Lens Tints

Lens At Execuspecs, we recognise each Indices person’s uniqueness and every lens and every frame must be carefully designed and fitted. As someone working in the eye care and eyewear industry, knowledge of lens coatings, designs and tints is imperative. Lens index refers to an optical property of the lens material. The higher the lens index, the thinner and lighter the lens will be. A higher index lens is generally a more expensive lens. The Optom will make recommendations according to the patient’s prescription, but the price of lenses will be a factor for some patients. mm Plus (+) Power Index Minus (-) Power mm 5.5 +4.00 -4.00 5.0 4.5 1.499 6.3 3.8 1.56 5.2 2.7 1.61 4.7 1.67 4.2 1.74 3.7 Example of lens indexes from 1.49 to 1.74 for a +4.00 and a -4.00 prescription

Plus and Minus Lenses Plus Lenses Minus Lenses The lens magnifies or enlarges an image The lens reduces an image size The lens produces a focal point on the opposite side The lens will not produce a focal point on the opposite to the image source side to the image source The centre of the lens is thicker than the edge The edge of the lens is thicker than the centre of the lens of the lens Prescribed for farsightedness / hypermetropia Prescribed for shortsightedness / myopia

Aspheric Lenses Normal Lens Aspheric Lens For the image conscious, , aspheric lenses (flatter high index lenses with edge-to-edge clarity) can make corrections without making the eyes look unnaturally large or small.

Lenses for Kids Children are playful by nature and generally active and sporty. It is recommended that children be given plastic lenses. Polycarbonate lenses, which are resistant to breaking, are the safest choice for children to withstand the rumble and tumble of a child’s activities. Scratch protection should be recommended for children.

Lens Coatings Hard-Coat / Anti-Scratch Coating This protective coating makes the lenses scratch-resistant NOT scratch-proof. All customer’s invoices will indicate this coating as a line item and a charge, but the Hard-Coat is a standard treatment for all lenses. UV Coating This protection blocks dangerous UV rays. It is like having a SPF (Sun Protection Factor) for our skin. Anti-Reflective Coating (ARC) / Anti-Glare This coating reduces eye strain and provides comfort when looking at screens, improves night driving by lessening the glare of oncoming headlights and enhances the cosmesis of the wearer versus uncoated lenses.

Blue Control Blue Control provides all the functions of ARC lenses with an added feature that they block out all harmful blue light. High energy Blue light is emitted from light sources including the sun, computer screens, smartphone screens and some lightbulbs especially LEDs. Polarised Polarised lenses in sunglasses keep out all reflected glare and are popular with those who participate in regular outdoor activities especially water sports. Polarised lenses are banned in fishing competitions as after the glare is removed, a wearer will be able to see the fish! Polarised lenses are the gold standard in sunglasses. None Polarised Polarised

Lens Designs Single vision (SV) Single vision lenses are prescribed to correct vision errors for one particular distance. The lenses have a single purpose and single focus which is either a spherical or astigmatic correction. SV lenses can be either plus or minus lenses, directly corresponding to the written prescription in power. Plus lenses are prescribed to correct farsightedness /hypermetropia, whereas Minus lenses are prescribed to correct correct short-sightedness / myopia. Bifocal (BF) The word ‘Bi’ means two and refers to the fact that bifocal lenses serve two purposes. They are designed to correct distance and near vision. The near portion is known as the addition or reading add or bifocal segment. Three designs of bifocal lenses are used: . Flat top (most common) . Executive (seldom used) . Round / fused (seldom used)

Flat tops are the most popular design as they are available in every kind of lens material and offer the bifocal portion in a variety of widths (28 / 35 mm), according to the patient’s needs. Bifocal lenses are ordered according to the following: . Power of distance . Add . PD at distance and near . Lens material . Size and diameter (in MM) . Size and design of reading addition . Tint . Additional coatings distance distance distance distance OR intermediate near near near near Single Vision Bifocal Vision Progressive Lens Lens Trifocal Vision Lens Lens Multifocal (MF) / Varifocal / Progressive Multifocal lenses enable much better vision than bifocal lenses, providing the same correction for distance and near sight but without the bifocal segment. This is achieved by using a blended design, without any ‘lines’, to give a transition from distance to reading. The multifocal lens is cosmetically appealing as there are no lines or visible reading segments. The design allows for a gradual increase in power to the near segment, which gives clear vision at the intermediate distances of vision (arm’s length) between, what may be focused on at a distance and what may be focused on close-up.

Accommodative Support Lenses These lenses are like multifocals, but have a lower strength for the reading segment These are recommended for a pre-presbyope who may be suffering with eye strain. Office Multifocal Lenses These lenses are like multifocals, but have no distance segment i.e. they have 2 distances with the intermediate at the top and the near at the bottom. These are recommended for those who spend most of their time working indoors without the frequent need for distance vision as one would when one is driving. Trifocal (TF) Trifocals are very seldom recommended or requested and are even difficult to source these days!

Lens Tints Both glass and plastic lenses may be tinted. The process of tinting differs in that glass lenses may be manufactured with a “solid” tint or lenses can be “coated” after surfacing and edging. Plastic lenses are manufactured in “white” and then immersed in a dye bath to result in the required tint. Tints may be: • Fixed i.e. lenses that are permanently one colour. • Gradient i.e. lenses that are permanently coloured but have a gradient from dark to light. • Photochromic i.e. automatically change darkness depending on surrounding UV light conditions.