Monday, August 31, 2015 12:11 PM
I love manual lensometry. If a fire were to suddenly threaten my boutique, I would grab my favorite vintage specs that belonged to my great-great aunt and my manual lensometer and then I would run for my life.
Tuesday, July 28, 2015 7:35 PM
Frame choice also drives material choice. Usually the patient will select their frames first and then the lenses. This can present a problem with some lens materials. Consider the combination of a plus lens and a grooved semi-rimless frame.
Wednesday, July 15, 2015 10:11 AM
When compared to CR-39 monomer, lenses made with Trivex material are up to 15 to 20 percent thinner and always about a third lighter. An aspheric design will further reduce thickness and weight. While there are other higher index materials that can make lenses even thinner, lightness depends on final lens volume and its specific gravity.
Wednesday, July 1, 2015 10:10 AM
Trivex material’s development has been consistent with the way new technologies build sophistication into products. In the past, a lens material had to be more closely matched with the prescription and the end results wanted. This is no longer the case.
Wednesday, June 10, 2015 10:05 AM
I was fortunate to have access to the NBS 1916 calibration set, from which I was able to make my own secondary set, which I still use today. Since I had confidence in their powers, it has proved especially useful. What does one do if there is a need to assess an instrument but one does not have such a set?
Wednesday, May 27, 2015 1:07 PM
In Part One of this three-part series, I described the history and early use the American Optical (AO) “NBS Truepower lens set” developed in 1916, which was used to assess the calibration of the AO Lensometer when first introduced to the market.
Tuesday, May 12, 2015 3:00 PM
I was recently asked what I thought was the most valuable item in the Optical Heritage Museum collection.
Monday, August 6, 2012 5:18 PM
Quick, what comes to your mind when the patient in front of you hands you this prescription, -13.00D sph O.U.
Monday, November 21, 2011 11:05 PM
The prescription, or lens formula, is the starting point for picking the best lens material, frames, and eye and bridge size.
Wednesday, November 9, 2011 10:48 PM
It starts with the prescription. The prescription (Rx)describes the patient's Refractive Error. Any Prism needed for the eyes to work together and an Add if needed for near vision/reading.
Wednesday, November 2, 2011 4:38 AM
So far we've learned the power at each of the principal meridians, the axis and 90 degrees from the axis. What happens in between?
Wednesday, November 2, 2011 4:03 AM
Here are some quick tips to be sure that the lens is returned from your lab as you expected - the last thing we want is a surprise...