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Using a lensometer to check glasses (Video)

length: 1:39 minutes

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.

Download this video for powerpoint

download.gifTo download this video, right click on a link below and choose “Save Target As…”

but.giflensometer.wmv (13 meg, Windows video file)
but.giflensometer.mp4 (13 meg, Ipod Video)


Thumbnails (click to enlarge photo)

lensometer1.jpg lensometer2.jpg lensometer3.jpg


Thanks for your help in refreshing my memory…video was very concise and useful…

Comment by Judith Whitehead — July 19, 2008

many thnx4 your help in education plz send education video 4 my e mail

Comment by mah owes — July 22, 2008

I’m glad you liked the video and thank you for commenting. Unfortunately, the video file is just too large in size to e-mail. You can download it directly, however, from the links above.

Comment by admin — July 22, 2008

thank for your help in education pls send education video 4 my email especial in slitlamp technic tk.

Comment by senmeng — September 1, 2008

Thanks for the help. I,m re-entering the job the work force as an optical dispenser. This was the best.

Comment by Cerise — November 10, 2008

Thanks for the help. I,m re-entering the work force as an optical dispenser. This was the best.

Comment by Cerise — November 10, 2008

thx alot 4 ur help in education plz send education video 4 my e mail

Comment by ibrahim — November 28, 2008

thanks a lot for the information. please kindly send me in my E Mail Address all more about lensomater technique in reading the amount of prism induce in the lens. thanks

Comment by sheila beto — March 4, 2009

thanks alot for all the information, it refreshes my memory. please kindly send me some slit lamp information technique. thanks.

Comment by sheila beto — March 4, 2009

Thx so much in education, wld u plz send education video 4 my e mail. Cheers.

Comment by Jacky — March 6, 2009

thanks a lot for the information.plz send some more video for minus number$ compound number on my e mail.

Comment by harshil — March 17, 2009

This flick just corrected 1 niche that i needed for perfection!

Comment by ROB — March 18, 2009

Very nice, thank you.

However, I did hear somwhere that one has to turn the glasses upwards to get the correct result for certain lense???

Comment by B — April 2, 2009

Went back into the wonderful field of optical again and thank-you for the refresher class on the use of the lensometer. Was very helpful. :) :) Just hoping to remember how to check prisms. THANKS AGAIN

Comment by Bonnie — May 6, 2009

thanks for help in education

Comment by daud — June 4, 2009

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


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

Comment by Yassin — November 12, 2009

thanks for this information…how do you check for prism in lenses….

Comment by cesar hernandez — November 13, 2009

Dear Rootatlas.com,

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.

Thank you.

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.
Jake Moore

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.

Comment by Mary — July 6, 2010

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!

Comment by Laura — July 22, 2010

very concise and helpful

Comment by Mohammed — July 24, 2010

Tu informacion esta barbara me ayudo muchisimo a refrescar mi memoria,podrias enviarme, algun ejemplo mas con prisma y si es un multifocal.Muchisimas gracias.

Comment by Laura — July 26, 2010

I appreciate the video that you have about then lensometer. Can you send me some more information about prism and the calculations on a lensometer?

Comment by Michael D. — September 7, 2010

how to check prism amount in lensometer ?

Comment by dhiviya — December 10, 2010

can u pls explain about the compound rx. + and – . Thanks.

Comment by sameer — January 9, 2011

This video is precise, concise and very lucid. It refreshed my memory and answered my questions spot on.
Thanks a lot.

Comment by Orsun Gun — March 5, 2011

Thank you for simplifying the use of the lensmeter. Is it possible for you to demostrate how to read the power of a lens in minus form.

Thank You.

Comment by kensa — March 11, 2011

Need help with prism please e-mail me prism video! Please

Comment by suzanne — March 29, 2011

You got a very good website, Gladiolus I noticed it through yahoo.

Comment by Lucien Cianflone — April 2, 2011

very useful thanks

Comment by krishnamurthy — April 12, 2011

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.

Comment by Trixmeti — July 21, 2011


Comment by khalid jamil — August 24, 2011

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
more power

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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