Phoropter

In 1909, Nathan Shigon of New York City invented[3] a monocular optometer with a range of +0.25 to +6.00 diopters, consisting of a mechanism where a disc of low-powered lenses advanced a second disc of higher power lenses automatically with each rotation, as in a modern phoropter.

There is no evidence this was ever manufactured, but in 1915 he filed for a patent for a binocular version of this same optometer,[4] and called it the Ski-Optometer, so named for its usefulness in doing skiascopy . This was manufactured by Wm. F. Reimold of Philadelphia. It included a Stevens Phorometer for measuring phorias, and a disc of auxiliary spherical lenses on the back, giving it a range of -12.00 to +12.00. To extend the range, there were clips on the front of each eye hole for the insertion of hand held sphere or cylinder trial lenses, with a mechanism to rotate the axis with the thumb. It weighed 2 lb. 3 oz.

Around 1916 Michael Woolf, also of New York City, bought him out and added his own invention,[5] an innovative battery of cylinder lenses, ranging from 0.25 to 2.00 D to the device, as well as Risley prisms for each eye. Maddox rods were optional. It was also called the Ski-Optometer, and it weighed 3 lb. 13 oz.

Around 1924 the patents and rights were transferred to General Optical Company of Mount Vernon, NY, which had been making a much larger, heavier and more solidly encased instrument, called the Genothalmic Refractor, since around 1920, using Woolf's 1917 patent number, and with a user's manual dated 1921. This instrument had a range of +17.75 to - 22.50 sphere, and up to 3.75 cylinder, Maddox rods, Risley prisms, and a Steven's phorometer. It weighed 7 pounds 5 ounces, and unlike all earlier devices of this kind, it hung from a horizontal mounting bar instead of being supported from the bottom. Like the Woolf, it had no Jackson cross-cylinders (JCC) at first, so a separate hand-held one was required. Late models of the Genothalmic were fitted with JCCs.

General Optical sold out to Shuron Optical of Geneva, New York, in 1927, which sold the refractor until the late 1930s.[2] A refined and improved version of the Genothalmic Refractor was manufactured in London starting around 1932, and sold in the UK by S. R. Stearman, S. Pulzer & Son Ltd., and others, as the British Refracting Unit (B.R.U.).

The early DeZeng/AO lineage. Top row: Model No. 570, 1917 or earlier, No. 584, 1922. Bottom row: No. 589, 1934, No. 590, 1948.

Also in 1909, Henry DeZeng got a patent for what looks remarkably like a modern phoropter,[6] but the patent illustrations look nothing like the manufactured product, which was introduced around 1915—the DeZeng Phoro-Optometer model 570. This was a device produced in Camden, New Jersey, which contained a battery of convex lenses for each eye, a battery of concave lenses for each eye, and auxiliary lenses which gave it a total power range of +15.75 to -19.75, as well as a Maddox rod and Risley prism for each eye, and a Steven's phorometer.

There were no cylindrical lenses, so testing for astigmatism required the use of manual trial-lenses, for which there were rotating holders on the front of each eye hole, and there were stationary ones on the backs as well. Cross-cylinders were optional, but they did not flip like a Jackson cross cylinder, they rotated in the same plane, so they were probably meant for the near point cross-cylinder test for reading.[7] It weighed 3 lb. 2 oz. Around 1920 an improved model, No. 574, was introduced, reduced in size but with the same range (lenses reduced from 1 inch to 3⁄4 inch). The forehead rest was removed, and the rear trial lens clips were replaced with rubber eye guards. It weighed 2 lbs. 12 oz.

In 1922, DeZeng replaced No. 574 with No. 584, and shortened the name to Phoroptor. This device became so popular that its name became genericized, though often spelled phoropter. The Phoroptor was smaller (lenses reduced again, to 9/16 inch diameter), with a similar power range, and the front clips for hand-held trial lenses were removed and replaced with batteries of cylinder lenses ranging from 0.25 D to 4.75 D. The Steven's phorometer was dropped, and there were no Jackson cross cylinders. It weighed 2 lb. 8 oz.

In 1925, American Optical bought DeZeng, and in 1927 introduced No. 588, the AO Wellsworth DeZeng Phoroptor, which was slightly larger; the lenses were increased to 11/16 inch and it weighed 3 lb. 2 oz. This was the first in the DeZeng/AO line to hang from a horizontal mounting bar, the earlier ones were supported from a bar below it. This phoroptor was unique in that it was calibrated in 1/8 diopter steps throughout its whole range.

In 1934, AO introduced No. 589, the Additive Effective Power Phoroptor, once again enlarged and improved. The lenses were increased to 3⁄4 inch diameter, the permanent size, and the unit was much more massive, with a weight of 7 lb. 9 oz., and with a range of +16.87 to -19.12 sphere and 6.00 cylinder, with auxiliary lenses to increase these to +18.87/-21.12 sphere and 8.00 cylinder. All these models resembled the original DeZeng model in design, but No. 590 of 1948 was a completely re-designed device, much larger and heavier, and more modern. It weighed 10 lbs. 7 oz. This was followed by another complete re-design in 1956, the RxMaster,[2] which became the prototype of all modern phoropters, and was updated to the Ultramatic RxMaster in 1967, which is the current model.

AO sold their phoroptor division to Reichert in 1982, who still make the Ultramatic.

What was available in 1934. Top left, the Genothalmic Refractor; top right, the AO 589 Phoroptor; bottom, the B&L Greens' Refractor, still much in use today.

In the early 20th century, ophthalmologists A. S. Green, L. D. Green, and M. I. Green, of San Francisco, CA, designed an optometer,[8] which they developed slowly over many years. The Greens teamed up with inventor Clyde L. Hunsicker of San Francisco, who applied for a patent on October 25, 1926. The title of their invention was simply an "optometrist instrument", and the text described it as an optometer. Patent 1,804,690 was granted to the Greens and Hunsicker in 1931, and sold to Bausch & Lomb (B&L), which had them redesign it (patent 1,873,356, granted 1932).

B&L trademarked it as "Greens' Refractor" and introduced it in 1934. It was far more advanced than the competition in many ways. The power could be read right off the dial without having to do mental calculations, the range was far higher, from +19.75 to -28.00 and with cylinders up to 7.50, the battery of cylinders was much more intuitive and easy to use, and it was the first to have Jackson cross cylinders affixed, (the first AO Phoroptors with JCC's were late models of the Additive, and very late Genothalmic Refractors also had them). It weighed 13 lbs. 1 oz. The Greens' Refractor soon became the gold standard among eyecare professionals. It helped put the Shigon/Woolf/Genothalmic line out of the market and forced AO to completely redesign their phoroptor from scratch, not once, but twice, (the 590 failed to compete).

The Greens' Refractor remained unchanged for over four decades, but sales slipped when AO introduced the Ultramatic RxMaster with its revolutionary yoked JCC in 1967, and production of the Greens' Refractor finally ended in the mid-1970s. In 1978, B&L introduced the Greens II refractor, also called the Bausch and Lomb Refractor, or the Greens' Mark II Refractor.[9] It included yoked JCC, but AO had already patented the yoking of the JCC, and production of the Greens' II was halted. Very few were made, and they are a rarity. It weighed 11 pounds 13 ounces. As for the original Greens' Refractor, in spite of the fact that production stopped decades ago, many are still being used today, as they are virtually indestructible, and have a devoted rank who still swear by them.[2]

Starting in the mid-20th century, companies in Europe and Asia have made phoropters of their own design, as well as copied American models. The Moeller Wedel Visutest of Germany, the Magnon RT 500 of France, and the Nikon Optester and Takagi MT3, both of Japan, are all of original design. The Topcon VT S of Japan is of original design, but Topcon has also made knock-offs of the Greens' Refractor and the AO Ultramatic. Rodenstock in Germany has developed many of their own models, as well as copied the Ultramatic with their Phorovist 200. The Marco RT-300 of Japan is an original design which borrows heavily from the Ultramatic. In the 1930s, Stearman in the UK and Ellis Optical Co., also in the UK, both made an improved version of the Genothalmic Refractor called the British Refracting Unit, and Stearman also made a knockoff of the Greens Refractor. China makes numerous unbranded knockoffs of the Ultramatic.