This video shows the use of a lensometer, a device used to check the prescription in glasses. This device can be tricky for the novice technician to use, as you must align the glasses well and move two dials at the same time to hone in on the prescription.
Here are the steps:
1. Place glasses on platform and secure
2. Turn axis and focus nobs so that the SMALL lines are straight and focused
Write down the number. This is your sphere.
3. Turn the focus nob until the fat lines become focused, and look at the new number on the focus nob. The DIFFERENCE from your prior sphere value is the CYLINDER value. If you changed from +1.00 to +4.00, then your cylinder is +3.00. If you changed from +1.00 to -1.50, then your cylinder is -2.50. In other words, the cylinder can be a positive or negative number, depending upon the direction you have to turn the focus nob.
4. Check the degrees on the axis dial. This is your cylinder axis.
If you want to check the bifocal add:
5. Move the glasses so that the bifocal segment is being read.
6. Turn the focus nob again until the fat lines again become focussed.
The amount of change needed to refocus the fat lines will give you your bifocal power.
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Great video! Are the measurements independent of the lens refractive index?
Comment by John Melaugh — July 9, 2009
Hey people, stop asking for junk to be sent “4 ur Email”. Learn some professionalism. Optical work isn’t done in a back alley you know.
Comment by Hank — July 14, 2009
THE ADD(BIFOCAL) POWER IS PROBALY A 2.25 ON THIS LENS. THE BIFOCAL POWER SHOULD BE CHECKED FROM THE BACK OF THE LENS, IE; FRONT VERTEX POWER FOR THE ADDED PORTION.
Comment by MARLIN — August 25, 2009
thanks for this information. How do you check for prism in lenses.
Comment by sherma — September 11, 2009
These videos are the God’s gift and sure Timothy Root’s gift to ophthalmic Residents. Definitely it is the bible for better eye knowledge. Thank you Timothy Root
I hope that you can make a video illustrating Keratometry Readings for calculation of intraocular lens (Non automatic keratometer) .
Thank you from Russia, Kursk state medical uniVersity
Thank you guys so much for showing me how to use the Lensometer! I just started an optician apprenticeship, and really needed to know how to understand how to use this thing:) You guys made it super simple and easy to understand:) Thanks again!
Comment by Markus — March 24, 2010
The one basic thing missing was telling the student about focusing for either plus or minus cylinder. It would also be nice to show how to measure for prism. Maybe you could do that at some point in time. You really have nice video presentations and I really enjoy your site.
Comment by Susan — May 12, 2010
Hi Tim Root
Congratulations on getting the number 1 google spot for lensometer. Hope all is well and BP doesn’t crush your dream of the beach front gulf coast home in Florida.
Comment by jake — June 25, 2010
That is a great Video! This type of information can be very useful when organizing staff meetings. What a great tool for the new hire.
Great video. I’m linking to it from a new site I just started for optician apprentices. It may be useful to also show what it would look like without a cyl and axis as well as what a prism would look like. Thanks!
Thank you for explaining in video it was very helpful!
Comment by Naomi — April 18, 2011
The add power was read incorrectly. The spectacles should’ve been “turned around” so that the add was read in front vertex power. On the compound hyperopic astigmatic lens you used in your example, you would’ve underestimated the add.
Comment by Arnie Patrick — May 11, 2011
Very simple to understand.thanks.i couldnt download the video though.
love this video,it helped refresh my memory.Thanks a tonne.
Comment by sylvia — September 6, 2011
thanks for your usefull website it really helped me
Comment by maliha — September 27, 2011
tnx alot so usful.
Comment by Noorullah — November 25, 2011
How did you get the video of the lensometer bars? We are trying to find a camera for ours for training purpsoes. Thanks
Comment by Shawn — December 12, 2011
is there one on checking prism in a lensometer
Comment by susan — March 9, 2012
thx a lot for training video,i never forgot this top video.plz mail it f me.thx
Comment by ali rad — March 13, 2012
excelent video!! would you show us how to check prims in rx? thank you very much for your time.
Comment by Nick — March 23, 2012
thank u my dear teacher
Comment by Ali Kareem — May 3, 2012
When reading the add power you always use the three separate lines,not the skinny lines?
Comment by Dean — June 22, 2012
Thank you, useful video for new users……….
Comment by Abid Ali Qureshi — August 11, 2012
nice video but what about the lensometers that require the optician to transpose the two readings? For ex. I have the NIKON OL-7 that the first reading in a miopic astigmatic lens shows -4,75 and the second -5,25 . What sign should i put and what about the ipermetropic astigmatic lenses. they always confuse me with the transposition! PLZ HELP !
Comment by Jimmy Chatzi — September 28, 2012
Don’t you need to read that high plus lens from the back surface to determain the add power? My experience is that the add power will read to strong if you only use the front surface.
Comment by Dana Hill — February 7, 2013
i think when ur reading from the forcemeter always consider your cyl sign 2 b negative e.g for positive sph take the more positive subtract it from the less positive to be able to get a minus cyl
Comment by monicah — March 9, 2013
hie? can you please send me videos of how to use a lensometer via my e-mail
Comment by alexx t chigona — September 5, 2013
Alexx, the video is too big to email, but the download link is above. Just RIGHT-MOUSE click on the link, and choose “Save Target …” to save the video to your computer. Good luck.
Comment by Tim Root — September 5, 2013
Comment by AQSASHOAIB — October 27, 2013
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