OpenOptix ABO Study Guide - Laramy-K Optical

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Trivex Developed in 2001 by PPG, Trivex combines impact resistance of polycarbonate, exceptional optical clarity, and a specific gravity of 1.11 (the lightest available). Trivex’s tensile strength makes it ideal for drill mount frames. Trivex is available from Younger as Trilogy and from Hoya as Phoenix. All Trilogy products are aspheric and guaranteed for life against stress fractures and drill mount cracking. Some Phoenix products are now available with aspheric curves. Index: 1:53 Pros Impact resistance of polycarbonate Better optical quality than polycarbonate Tintable Lightest material on the market Inherent UV protection High tensile strength (ideal for drill mounts) Cons Susceptible to scratching (correctable by coating) Lens Material Properties Summary Lens Material Properties Material Index Specific Transmittance Transmittance Gravity UVA (286 - UVB (320 - (g/cm3) 320 nm) 380 nm) CR-39 1.50 1.32 58 4.0 10.3 0.0 Poly 1.58 1.21 29 5.2 0.0 0.0 1.60 (MR6) 1.60 1.22 42 5.3 0.0 0.0 1.66 (MR7) 1.66 1.35 32 6.2 0.0 0.0 Trivex 1.53 1.11 46 4.4 0.0 0.0 Crown Glass 1.52 2.54 59 4.3 84.3 30.5 1.60 Glass 1.60 2.60 42 5.3 39.1 0.1 1.70 Glass 1.71 3.20 35 6.7 24.6 0.0 1.80 Glass 1.81 3.66 25 8.2 19.5 0.0 This document is licensed under the Creative Commons Attribution 3.0 License. 7/30/2009 34
Principles of AR Coatings As light passes through a lens, it experiences a change in index of refraction. Subsequently, some of the incident light is transmitted through the lens medium and refracted while some of the light is reflected. This reflected light is not only perceived by others as glare, but also represents a loss of light transmitted through to the eye. As the refracted light continues through the lens medium and reaches the back surface of the lens, there is another index change and again refraction and reflection occur. Reflected light here can bounce off the internal surfaces of the lens and be seen by the patient as blurred or ghost images. Others may see internal reflections as multiple rings inside the lens (most prevalent in high minus powers). Blurred or ghost images can become intensified at night around bright lights common in dusk or night time driving conditions, and can significantly impair vision. Also, this backside reflection represents further loss of light transmitted through to the eye. Light incident upon the back surface of a lens will also undergo a certain amount of reflection. Light here can be reflected directly back to the eye. The resulting images can be a distraction to the wearer or can, in certain conditions, impair vision. For example, bright sun light hitting the back surface of a sun lens that is not AR coated, depending on the angle, can either be reflected directly back into the eye or can "fill" the lens with reflected light. Either case can result in significant vision impairment. AR coating can minimize lens surface reflections, significantly reducing or eliminating the problems discussed above, reducing eye strain, while allowing more light to reach the eye, improving contrast and clarity. How AR Works AR coating reduces lens surface reflections by actually generating reflections of its own. The index of refraction of the AR layer is in between that of the lens medium and that of air. Light incident upon an AR coated lens experiences reflection at both the AR layer and the surface of the lens. However, the thickness of the AR layer is such that the light waves reflected from the AR surface are 180° out of phase with light waves reflected from the surface of the lens. Consequently, the reflected light waves undergo destructive interference and effectively cancel each other. The Law of Conservation of Energy states that energy can neither be created nor destroyed. So, what happens to the energy from the cancelled light waves? It is transferred through the lens medium to the patient’s eyes improving contrast and clarity! This document is licensed under the Creative Commons Attribution 3.0 License. 7/30/2009 35
Page 1 and 2: OpenOptix ABO Study Guide Ver. 1.3
Page 3 and 4: DOCUMENT SPONSORS AND CONTRIBUTING
Page 5 and 6: Scratch, UV, and Mirror Coatings...
Page 7 and 8: epithelium and Bowman’s Membrane
Page 9 and 10: Myopia Myopia, also known as near-s
Page 11 and 12: Anisometropia is a condition in whi
Page 13 and 14: Chapter 2: BASIC OPTICAL PRINCIPLES
Page 15 and 16: The straw seems to be broken, due t
Page 17 and 18: images seen by both eyes, so the ey
Page 19 and 20: Chapter 3: LENS FORM Sphere It can
Page 21 and 22: The corrective power of a lens is d
Page 23 and 24: Most prescriptions have some combin
Page 25 and 26: A lens measure has three points of
Page 27 and 28: Curve Eccentricity Circle e = 0 Ell
Page 29 and 30: Transposing Prescriptions Transpose
Page 31 and 32: Reflectance The reflectance of the
Page 33: Pros Thinner and lighter than glass
Page 37 and 38: lenses are finally available for sa
Page 39 and 40: ack surface of the lenses. While po
Page 41 and 42: n = index of the main lens n s = in
Page 43 and 44: To find the optical center of the s
Page 45 and 46: wider and less distorted making it
Page 47 and 48: seen as signatures which continue t
Page 49 and 50: Occupational Lenses In the broadest
Page 51 and 52: Basic impact lenses must: • Have
Page 53 and 54: Calculate a Slab Off Example: OD -5
Page 55 and 56: The first multi-focal lens type we
Page 57 and 58: Effective Diameter (ED) - Twice the
Page 59 and 60: Nose pads: Nose pads are the small
Page 61 and 62: Hinge: The hinge is the point where
Page 63 and 64: Advantages of stainless steel frame
Page 65 and 66: Plastics really have one general ca
Page 67 and 68: We are often asked if the frames on
Page 69 and 70: The last temple type was once calle
Page 71 and 72: NO! This plastic frame makes very l
Page 73 and 74: YES! In this figure the pads are ma
Page 75 and 76: Secondary Frame Fitting Considerati
Page 77 and 78: Frame Misalignment X-ing Skewed out
Page 79 and 80: Temple Fit Ideally, the temples sho
Page 81 and 82: Vertical angle - The angle of the p
Page 83 and 84: Adjusting the endpieces is preferab
Page 85 and 86:
Part Identification 1. Eyepiece 7.
Page 87 and 88:
6. Eyeglass Table - The eyeglass ta
Page 89 and 90:
which should be documented along wi
Page 91 and 92:
Common Handtools for Frame Adjustme
Page 93 and 94:
Other Tools and Instruments Pupilom
Page 95 and 96:
(R2004) ANSI Z80.25 - 1996 (R2002)
Page 97 and 98:
Cylinder Power For Progressives Cyl
Page 99:
DOCUMENT LICENSE This work is licen
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