OpenOptix ABO Study Guide - Laramy-K Optical

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Cons Does not accept tint Not impact resistant Heavy CR-39 Developed by PPG during WWII, CR-39, also known as plastic or hard resin, serves as a much lighter lens material (approximately 50% lighter) than glass. CR-39, however, is far less scratch resistant and often must be coated to improve its scratch resistant characteristics. Index: 1.498 Pros Lighter than glass Readily tintable Less likely to fog Cons Susceptible to scratching (correctable by coating) Lower index of refraction makes it less suitable for higher powered prescriptions Polycarbonate While its optical characteristics are less than ideal, polycarbonate, the same material used for bullet-proof glass, is the most impact resistant of lens materials. Consequently, polycarbonate is the material of choice for safety and children’s eyewear. With an index of 1.59, polycarbonate also produces thinner, lighter lenses than glass or plastic. These factors along with polycarbonate’s inherent UV protection and pricing make it a popular material. Index: 1.59 This document is licensed under the Creative Commons Attribution 3.0 License. 7/30/2009 32
Pros Thinner and lighter than glass and plastic Highly impact resistant (used for safety glasses) Inherent UV protection Cons Poor optical quality Susceptible to scratching (correctable by coating) Susceptible to stress fractures in drill mounts Does not readily accept tint Hi-Index High index lenses polymers typically refer to products with an index higher than 1.58. High index lenses require flatter curves than their lower index counterparts, resulting in thinner and lighter lenses. Furthermore, aspheric curves come standard in many high index products, particularly 1.66 and 1.70 products, and are available in 1.60. Asphericity reduces spatial distortion, reduces magnification or minification, and further helps maintain a thin and flat lens profile. High index material, however, tends to have a lower Abbe value which could potentially affect patients who are sensitive to chromatic aberration. Also higher index and flatter curves tend to result in more backside and innersurface reflections. AR coatings are usually recommended for high index lenses to eliminate these reflections. Index: 1.60, 1.66, 1.70 Pros Thinner and lighter than glass and plastic Better optical quality than polycarbonate Cons Susceptible to scratching (correctable by coating) Susceptible to backside and inner-surface reflections (correctable with AR) This document is licensed under the Creative Commons Attribution 3.0 License. 7/30/2009 33
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: Reflectance The reflectance of the
Page 35 and 36: Principles of AR Coatings As light
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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