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A Rose By Any Other Name
Karlen McLean, ABOC, NCLC
As with many things in the optical business, the names of systems and products can be confusing. A singular system or product can have multiple names.
A topic of lively debate at The Vision Council's Optical Forum, the industry is still trying to land on one definition for free-form/digital. Is it a process, a surface, a lens, or something else?
This isn't the first multi-name game. When I was a new dispenser learning the nuances of true opticianry, I struggled with trying to determine the proper name for one piece of equipment we use in our practices each and every day. In the past I called it lensometer, but there are at least six names associated with this tabletop device that ECPs use to read the dioptric power of Rx lenses.
PHAKOMETER: Introduced in 1876 by Hermann Snellen, it measured power and located the optical center of only convex lenses.
DIOPTRESCOPE: A trade name used by Keeler in the late 1940s; production ended in the early 1950s.
VERTOMETER: The trade name of Bausch & Lomb and Reichert Ophthalmic Instruments. Neither is in production today.
LENSOMETER: The name of American Optical's instrument, also no longer made.
AO Lensometer from 1921; courtesy of the Optical Heritage Museum
FOCIMETER: Typically a British term for lensmeter, it is used by the College of Optometrists in London.
LENSMETER: The worldwide general term for the instrument used to measure and verify Rx lenses. While there is no right or wrong term, I've decided to make the choice for one particular term.
Unless I'm speaking directly about the out-of-production vertometer or lensometer—and not using British vocabulary—my pick is the general term ‘lensmeter' as the best overall descriptive name. EB
| DID YOU KNOW |
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| You probably know that lensmeters can be automatic or manually operated. But did you know: |
| 1 There are two types of lensmeter targets: a dot target (circle of dots) and a line target (crossed lines). 2 The first lensmeter that passed light through a lens was introduced in 1912. Prior to this, lenses were hand neutralized, a lens measure (a lens clock or spherometer), or phakometer, was used. 3 American Optical introduced the AO Lensometer in 1921. 4 Green filters were added in the early 1900s to help reduce the amount of chromatic aberration. 5 Projection lensmeters were introduced to the market but never became a widely used technology. 6 Gas/oxygen permeable contact lens powers can be verified using a lensmeter. Place the contact lens concave side on the stop and focus until clear; read power. |
| Senior editor Karlen McLean has been in the optical industry for 35 years. She has spent half of that time in the dispensary. In this monthly column, Karlen shares her own experiences, and hopes you'll share yours. Contact her via email at Karlen.McLean@WoltersKluwer. com or online at Facebook.com/eyecarebusiness. |
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