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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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!
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.
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!
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 Abid Ali Qureshi — August 11, 2012 @ 8:08 am
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 @ 5:12 am
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.