Optical History

AO (American Optical) Trial Set – 40 Years Of Research

January 20, 2016

You will soon know that we are obsessed, not only with the history and design of vintage eyewear, but also the history of refraction; when and how it began.  With technology now days, walking into your Optometrist’s office, you are least likely to see one of these, a trial set.

AO trial set - Colorado 1

AO Tillyer Trial Set from the 1920’s, most likely 1926 – we found this treasure at an Antique Market in Fort Collins, Colorado.

Nothing is more important to a refractionist than his trial set.  It is his means of providing his patients with accurate Rx lenses.  A trial set is a refractionist’s “court of final appeal” in eye examination work.  The American Optical Company had long recognized the importance of trial lenses and had been experimenting for more than half a century on trial sets.  Up to 1890, American made trial sets were not considered to be of great importance in refraction.  The professional men prided themselves on their “imported” sets.

George W. Wells, late president of the American Optical Company, engaged Dr. Charles F. Prentice, a noted optical scientist, to make a special study of trial lenses.  Thus, before 1899, AOCo. in collaboration with Dr. Prentice, developed a trial set with bi-concave and bi-convex lenses which exactly neutralized each other.  Although made over thirty years ago at this point, the spheres in these sets were effective power!  Sometime later, the need for establishing a better fixed standard for trial lenses became apparent.  The American Optical Company made three master trial sets with a lens range of .12D to .20D, one of which was measured and certified, and there after became the AO primary standard set used as the basis for all AO measurements of lens power.

In 1926, American Optical Company introduced its foremost advance in trial sets – The Tillyer Trial Set, the result of twelve years of continuous research by Dr. Edgar D. Tillyer, Chief of the AO Research Division.  The outstanding advantage of the Tillyer set is its additive accuracy which permits final Rx readings which are exact and final.  The difference between the Tillyer trial set and ordinary trial sets is that the Tillyer reads exact effective power even though sphere and cylinder lenses are used in combination.  In other words, it eliminates so-called allowances.  Thus, through these improvements and during a period of forty years at this time, AO had led in the development and distribution of trial sets that had helped give patients the most comfortable correction for their eyes.

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