Module 19 
 

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Module 19:

Clinical Optics:

Part 3
 

 

Measurements, Calculations,

Adjustments, and Formulae
 

 
 

OVERVIEW
 

 
 

Estimated study time:  One hour.

 

Program Level:  Intermediate and Advanced 

 

Target Audience:  OMPs wanting to understand useful mathematical concepts relating to clinical optics.  OMPs studying for the COT and COMT exams.

 

Pre-requisites:  A knowledge of basic algebra is helpful.

 

Date of original release:  March 7, 2003
 

 
   
 

Description of content:  This module discusses measurements, calculations, adjustments, and formulae common to clinical optics.  Examples are given and applications are discussed.  Included are:

  • PD measurement

  • frame PD and lens decentration

  • spherical equivalent

  • transposition

  • axis cross and power cross

  • lens power at 180 and 90

  • vertex distance

  • focal distance and diopter power

  • focal distance for non-parallel light

  • prism diopter

  • induced prism

  • converting K readings to cylinder correction

  • radius of curvature and diopters

  • base curve and ocular curve

 

Instructional  objectives:  Upon completion of  this section,  the student should be able to:

  • describe the procedure for measuring the PD

  • compute total lens decentration from frame measurements and PD

  • compute the spherical equivalent of a prescription

  • transpose a prescription

  • construct a power cross and an axis cross

  • describe what the power cross and the axis cross can be used for

  • compute the power of a lens in the 90 degree meridian

  • compute the lens power for a change in vertex distance

  • describe how to do a vertex power computation for a sphero-cylinder

  • compute the focal length of a lens for infinity and other distances

  • compute light deviation from a prism

  • convert K readings to a cylindrical correction

  • compute diopter power from radius of curvature

  • compute base curve and ocular curve
   
 

About the Author: Gary Gallimore is a certified ophthalmic technologist who assists with research at the Eye Foundation of Kansas City and works for a large multi-specialty ophthalmology practice in the metro area of Kansas City.   He has taught CE courses for many years on all subjects of ophthalmic technology. 

 
   
 

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