Vision to Educate. The Basics of optics. 10 essential pages

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Liliana Washington
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1 Vision to Educate 10 essential pages Edition 2014

2 Introduction Edito If it is impossible to summarize the professionofopticianinabookletof12pages,wehave tried in this paper to provide enough information to allow the formation of employees in a store. The philosophy of such a document is to bring you an ever more concrete than verbal explanations support and remain a benchmark in store. Itis notintendedtoreplaceatraining. The profession of optician is multifaceted, both technician, paramedical actor and businessman. It must always be remembered that its mission is to enable its customers to see well by providing an appropriate response to their needs and comfort. Summary 1. Basics 2. Anatomy of the Eye 3. Ametropias 4. Unifocallens and centering 5. Organic vs. Mineral 6. Spherical vs. aspheric coatings 7. Photochromism and tintings 8. How thin glass? 9. Compensation of presbyopia 10. The progressive lens 11. Adaptation rules The basics of optics

3 1. Basics Convergence function vs divergence function Direction of propagation of light Direction of propagation of light Convergent Lenses concave convex Divergent Lenses concave The diopter(δ or dt) is the unit of measurement of the power of a glass. A glass can have a positive power (converging lens) or a negative power (diverging lens). A glass with a power of means it is converging rays from infinity to 1m behind the lens (if the power was dt, this would mean that the rays converge 50 cm). +1,00 d 1 meter F

4 2. Anatomy of the Eye What you can see. The eye is about 24mm in diameter The eye focuses like a lens-it has a power of about 60 Dioptres! Pupil What you can t see. Iris Pupil Cornea Iris Cornea Sclera Retina Macular Lens Pupil- where light enters the eye Iris-the coloured part of the eye-works like an aperture Cornea-Very thin membrane that bows over the iris-it is a powerful Plus lens (about +40D) Sclera-the white part of the eye that maintains shape Retina-the light sensitive tissue that lines the inside of the eye Macula-the region of the retina that provides the best vision-if you are reading this you are using the macular region. It is about the size of this o. Lens-The lens sits behind the pupil-it is a powerful plus lens (about +20D) Sclera The basics of optics

3. Ametropias Emmetropia Myopia Hypermetropia Astigmatism I see clear at every distance without

I see better away than closed, my eyes are quickly tired. I have a vague vision at every distance.

The myopic eye: the image is formed before the retina.

5 3. Ametropias Emmetropia Myopia Hypermetropia Astigmatism I see clear at every distance without effort. I see blur away but clear at near distance. I see better away than closed, my eyes are quickly tired. I have a vague vision at every distance. I confuse letters. The emmetropic eye: the image is formed on the retina. The myopic eye: the image is formed before the retina. The hypermetropiceye: the image is formed after the retina. The astigmatic eye: the curvature of the cornea is slightly oval. The image is distorted. Concave lens Convex lens Astigmatic lens R r R Spheric lens Toric lens R

6 4. Unifocal lens and centering The essential Unifocallens= lenswithone power only The power : itdependson what? S n R C The toric lens: the transposition +1, ,00 D = power (diopter) n = index of refraction R = radius of curvature SC (m) (-2,50) (+2,50) D = +1,50 n - 1 R 30-1,00 It depends on The index of the lens The radius of curvature Lens witha power from-1,00 to 30 and +1,50 to 120 In cylinder ,00 (+2,50) 30 In cylinder- +1,50 (-2,50) 120 sphere cylinder axis The centering Boxing vs datum B B A A D D Measurement of ½ pupillary distance Optician Pd Pd h h Settings of FV, IV, NV Settings of RE and LE reticles DATUM system Traditional norm Measuring the height witha ruler BOXING system Manufacturer lenses norm. By default standard on automatic edgers.

7 5. Organic vs mineral Mineral Organic In organic: Name Index Drill ability Compulsory AR ORMA 1,5 ORMEX 1,56 AIRWEAR (polycarbonate) 1,59 Advisable Todaya CrizalForte organiclensisas resistantas an anti-reflective mineral lens. Polycarbonate, an ultra shock resistant lens. In mineral: ORMIX 1,6 Advisable STYLIS 1,67 Yes LINEIS 1,74 Yes Name Index Drill ability Compulsory AR STIGMAL 15 1,5 STIGMAL 16 1,6 Advisable STIGMAL 17 1,7 Yes STIGMAL 18 1,8 Yes STIGMAL 19 1,9 Yes

6. Aspheric lenses Coatings Design primarily to be optically better.

providing the same power whatever the wearer intends to look.

spherical glass where the measured power is the same over the entire surface while the

Hard coating Purpose: to fightagainstscratches How?

organic glass Spherical lens Aspherical lens Spherical lens A specific centering Aspherical

ahead: we can then measure the mounting height.

8 6. Aspheric lenses Coatings Design primarily to be optically better. Make an aspheric design is primarily intended to provide a better vision to the wearer by providing the same power whatever the wearer intends to look. This means that the lens power (measured power) varies according to the eccentricity unlike a spherical glass where the measured power is the same over the entire surface while the perceived power varies. Design to have a flatter and thinner glass. Hard coating Purpose: to fightagainstscratches How? Depositing a layer of nano-composite varnish for increasing the scratch resistance of the organic glass Spherical lens Aspherical lens Spherical lens A specific centering Aspherical lens The wearer leans back so that the surface of the lens is vertical while looking straight ahead: we can then measure the mounting height. Anti-reflective lenses Purpose : Fight against unwanted reflections, unsightly and penalizing. How? Depositing a layer of nano-composite varnish for increasing the scratch resistance of the organic glass The optical center of the lens must be 1 mm below the pupil every 2 degrees of pantoscopic angle.

7. Photochromism and tintings The photochromic treatment Purpose: Provide visual comfort by offering glass tinting variably depending on

in the material in the case of mineral lenses (focus in the case of high power, the aesthetic result is not good because of the differences

Attention: Deposition of a colored layer reducing the transmission of visible light.

harmful than nothing to wear. Polarized lens Know : - The lower the temperature, the higher the treatment reacts.

9 7. Photochromism and tintings The photochromic treatment Purpose: Provide visual comfort by offering glass tinting variably depending on ambient brightness. How? By integrating the ophthalmic lens UV reactive molecule. in the material in the case of mineral lenses (focus in the case of high power, the aesthetic result is not good because of the differences in thickness). depositing a specific layer on the surface in the case of organic glasses Tints Purpose: Fight against glare How? Attention: Deposition of a colored layer reducing the transmission of visible light. Tinted glass does not mean good solar protection, the material must also filter out 100% of UV, if this is not the case, the color is more harmful than nothing to wear. Polarized lens Know : - The lower the temperature, the higher the treatment reacts. - Working with UV treatment is less effective behind a car windshield. Purpose: Fight against glare and provide additional comfort by eliminating reflected light on surfaces (water, snow, sand, windshield...) How? Polarizing filter sandwiched in the glass (be carreful with the nylor mounting )

8. How thin a lens? prerequisite: the size and shape of the former have a major impact Material (index) How doesitwork? Withequalpower the higherthe index the thinner the lens n=1,5 +4.

convex lenses if chooses a small frame and therefore a small diameter the lens will be thinner at the center and therefore on the edges Precal For convex lenses the best result is obtained

10 8. How thin a lens? prerequisite: the size and shape of the former have a major impact Material (index) How doesitwork? Withequalpower the higherthe index the thinner the lens n=1, D Diam : 65 n=1,6 5,4 mm 4,8 mm Design (asphericalvs spherical) With equal power and material the aspherical lens is thinner and flatter than the spherical lens n=1,6 4,6 mm Diameter For convex lenses if chooses a small frame and therefore a small diameter the lens will be thinner at the center and therefore on the edges Precal For convex lenses the best result is obtained by ordering a lens specifying the design and the centering. The supplier optimizes then the thickness with equivalent material and design Standard lens Ø70 Precal lens plano (+2.00) 0 plano (+2.00) 0

9. Compensation of presbyopia Presbyopia: loss of accommodative power : With the best FV correction NV

retina Different solutions for compensating presbyopia: Unifocal lenses Degressive lenses Progressive lenses FV

lenses as soon as you want to see beyond 50 cm.

11 9. Compensation of presbyopia Presbyopia: loss of accommodative power : With the best FV correction NV Inadequate accommodation Perceived blurred image NV Inadequate accommodation Adding convex Sharp image on the retina Different solutions for compensating presbyopia: Unifocal lenses Degressive lenses Progressive lenses FV IV NV Practical FV IV NV Practical VFV IV NV Practical Only a vision for near vision, necessary to withdraw your lenses as soon as you want to see beyond 50 cm. A lens with near vision with a decrease in power at the top to allow comfortable intermediate vision. A clear vision at all distances, to wear them permanently or not according to your needs.

10. The progressive lens Whatisa progressive lens?

Far vision Intermediatevision Vertex= 12mm Pantoscopic angle = 8 Wrap angle= 7 Nearvision This power variation causes aberrations, needing a training period.

lens : I keep my head straight and lean my eyes The adjustment of the frame is key to get closer to its maximum value and provide optimal vision.

12 10. The progressive lens Whatisa progressive lens? A glass designed for precise position before the eye : It is a lens with a variation of progressive power enabling presbyopic to have whatever distance it looks clear vision. Far vision Intermediatevision Vertex= 12mm Pantoscopic angle = 8 Wrap angle= 7 Nearvision This power variation causes aberrations, needing a training period. To see far vision (landscape) look straight ahead If I need to watch on the sides : I turn the head If I look on the ground : I lean my head To see near ( read) Look on the bottom of the lens : I keep my head straight and lean my eyes The adjustment of the frame is key to get closer to its maximum value and provide optimal vision. What is the meaning of gouache and micro-prints? Distance Reference Circle Fitting Cross Prism Reference Point Micro-etching To use the intermediate vision (computer) I adjust my head carriage The centering Interpupillary distance FV and full pupil height (watch boxing vs Micro-etching Temporal Add Power Material Nasal datum) and of course frame preajusted. Near Reference Circle Right Eye Lens Logo

11. Adaptation rules Discover The customer Whatdidthe wearerwear? Whatare hisvisualneeds?

Preajustement of the frame Measurementof the ½ interpupillarydistance (pupillometer) Measurements of pupillary

13 11. Adaptation rules Discover The customer Whatdidthe wearerwear? Whatare hisvisualneeds? Analyse the prescription The choice of a right frame Take measures Achieve mounting Did the prescription change much? Doesthe addition correspond to hisage? A frame respectingthe Far Vision An adjustable frame allowing a good pantoscopic angle (between 8 and 12 degrees) Preajustement of the frame Measurementof the ½ interpupillarydistance (pupillometer) Measurements of pupillary heights(ruler, careful : datum measure) Boxingor datum Centering full pupil Mounting Deliver the equipment Monitor adaptation Ajustment Check up of the centeringand the vision Advise, explain, demonstrate Recall the client to know if it is satisfied after a few weeks

14 Vision to Educate

PART 3: LENS FORM AND ANALYSIS PRACTICE TEST

PART 3: LENS FORM AND ANALYSIS PRACTICE TEST 1. 2. To determine the power of a thin lens in air, it is necessary to consider: a. front curve and index of refraction b. back curve and index of refraction