OpenOptix ABO Study Guide - Laramy-K Optical

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Since a spherical curve is the same in all meridians, if a -2.00 D spherical curve is combined with a +4.00 D cylinder at 45º, we end up with a compound lens described by the power cross below. These curves on the lens surface can easily be measured with an instrument called a lens measure or lens clock. This document is licensed under the Creative Commons Attribution 3.0 License. 7/30/2009 24
A lens measure has three points of contact which are placed on the lens surface to measure its curve. The outer two points are stationary while the inner point moves in or out to measure the sagittal depth of the lens. From the sagittal depth the instrument indicator displays the curve in diopters, with plus (+) curves shown in one direction and minus (-) curves in the other. The lens measure can also be used to determine whether a lens surface is spherical or toric by placing the lens measure on the optical center of a lens and rotating the instrument about the center. If the indicator does not move while rotating, the surface is spherical. If the indicator changes when the lens measure is rotated, the lens surface is toric, with the minimum and maximum readings corresponding to the meridians of power. When using a lens measure, keep in mind the instrument is calibrated to read powers of lens materials with a refractive index of 1.53, therefore higher index materials will have a true power greater than the indicated measurement. With a lens measure, the power cross, and the total power equation (F 1 + F 2 = F Total ) it is possible to determine the nominal power of spherical and toric lenses. For example, if we use the lens measure to find the curve on the front surface of a lens to be +4.00 D in all meridians and the curve on the back surface of the same lens to be -2.00 D in all meridians, we know the curves are spherical and can determine the total power of the lens as follows: This document is licensed under the Creative Commons Attribution 3.0 License. 7/30/2009 25
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: Most prescriptions have some combin
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 and 34: Pros Thinner and lighter than glass
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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