Inventions seldom proceed smoothly and may arise from research directed
to other ends or unexpected observations. Teflon, for example, was discovered
as a residue of chemical reactions designed to produce something else and
was only "noticed" because it was a waste product hard to remove.
Nor is the law of unexpected consequences shy to raise its head. For
example, the original optometry acts contained medication bans not at the
request of medicine, but at the request of our forefathers. This was because
Prentice, in New York, who triggered the issue, had been accused of practicing
medicine without a license only after he began to charge for his examinations
and his defense was characterized by the "A Lens Is Not A Pill" pin that
early optometrists began to wear and hand out to politicians. Thus, when
the first licensing acts were written it was optometry that insisted they
exclude medications while organized medicine insisted they not be required
to hold an optometry license to refract.
And much of history is unrecorded. Have you ever wondered why the first
optometry licensing law was enacted in Minnesota in 1901 when the action
seemed to be around Prentice in New York? Last year I happened to sit next
to two officers of the Minnesota Optometry Association at lunch and I asked
them about this. They said they had wondered themselves but had been unable
to secure the early records due to a fire but, they hoped to one day solve
this puzzle.
In the late 1950's, Bernard Grolman, O.D., a member of the Research
and Development Group at the American Optical Corporation in South Bridge,
Massachusetts felt insulted while driving to work after hearing a radio
"public service" announcement proclaiming only medical doctors were able
to protect the public from the danger of glaucoma. This "public service"
ad had been paid for by the Massachusetts Society of Ophthalmologists and
Bernie once told me that "personal annoyance… really anger, led me to consider
diverse non-contact means of IOP measurement". At that time no state allowed
optometrists to use medications and it wouldn't be until the early 70's
that the first licensing law was changed to include diagnostic agents.
Thus optometrists could not use the Goldmann tonometer and this radio ad
used this instrument as a marketing tool. This radio ad however, led to
unexpected consequences.
In those days optometrists were mainly limited to using the McKay-Marg
tonometer that, in principle, didn't require corneal anesthesia but wasn't
easy to use and required tapping a small sensor probe (covered by a thin,
rubber boot) against the cornea and interpreting an inked graph the sensor
produced. Using the MaKay-Marg was difficult and, because it was then still
widely believed that only those over 40 needed tonometry (a court had yet
to rule tonometry ought be performed on everyone), many optometrists did
not measure IOP.
As a result of that radio ad, Bernie Grolman, a quiet, polite and precise
man, spent most of his next 10 years designing and painstakingly testing
a new tonometer that would change our professional lives and become widely
used throughout the world.
He graduated from the Brooklyn Polytechnic Institute in 1942 and had
worked for GE as a draftsman before serving as a Navy radarman from 1944
to 1946. After discharge he apprenticed as a diamond setter but began to
experience visual problems and consulted an optometrist who solved his
vision problems and interested him in optometry. Grolman entered Hofstra
College under the GI Bill as a pre-optometry student and in 1952 graduated
from Columbia University's optometry program with a B.Sc. and M.Sc in optometry
and became licensed to practice.
Ironically, due to professional politics, Columbia's optometry program
(a part of the physics department) was later forced to close but this led
to the founding of the Optometric Institute of New York which became the
SUNY State College of Optometry; due primarily to Dr. Norman Haffner's
untiring efforts over a 30 year period. Like Grolman, Haffner only works
harder when told something can't be done. And prejudice by one profession
against another is anathema to both men.
By the time he completed his optometry degrees Grolman "was confronted
with serious doubts about my ability or desire to service the public" and
was attracted, instead, to optical engineering and became a development
engineer at the Burroughs Business Machines Corporation designing and testing
optical, telescopic missile tracking systems from 1952 to 1955. While this
work was "interesting and challenging" it had little to do with the eye
so when given an opportunity to join American Optical he "jumped at the
chance".
After hearing the radio spot, Grolman wondered how he might measure
IOP without "touching" the eye and came to believe that the eye, a fluid
filled globe, should have a resonant frequency of mechanical vibration
that would depend upon the IOP--- eyes with higher IOP would resonant at
higher frequencies. Every object has a resonant frequency of vibration,
a frequency at which it most easily vibrates. Bells, tuning forks and piano
strings for example, but also other objects, even buildings and bridges.
Most people have owned a car with a resonant vibration frequency at a certain
speed---go faster, or slower, and the vibration is less. And buildings
that collapse during an earthquake may have resonant frequencies close
to those of the earth tremors.
Grolman reasoned that the eye's natural resonant frequency of vibration
should, like a piano string, vary with its tautness and eyes with higher
IOPs would have higher resonant frequencies. He thought that if he could
develop a table of ocular resonant frequencies Vs IOPs an instrument that
measured an eye's resonant frequency could be used, with this table, to
determine IOP. Just as a Schiotz tonometer reading was converted into IOP
using a table.
His work then was to learn how to induce, and measure, resonant eye
vibrations and document how they varied with IOP and devise a non-contact
clinical instrument that could measure any eye's resonant frequency.
The first step was to get an eye to vibrate at its resonant frequency
and now the unexpected occurred. Grolman had begun by directing sinusoidal
sound waves of increasing pitch from a loud speaker to an eye on which
a high-speed camera was focused to record any vibrations. He found he could
produce an almost step function corneal "displacement" using a noisy discharge
from an automobile spark plug to drive the speakers.
To his surprise he found the high-speed film frames (5,000 frames/second)
showed these air pulses striking the cornea were flattening its apex but
not exciting ocular vibrations. He had failed to induce vibrations but
had found a pulse of air could applanate the cornea.
After years of further empirical study and seemingly countless designs, Grolman produced a single stroke, solenoid-activated air pump that, connected to a tube of certain dimensions, produced an air pulse of increasing (ramp-like) pressure that lasted but a few milliseconds yet applanated the corneal apex like a Goldmann tonometer's tip. The applanation was reproducible and grew in size as the air pressure grew with time and, since the air pulse's pressure increased linearly with time, he could determine the pulse pressure required to produce a standard amount of applanation by measuring the time it took to do this. If he knew the time he knew, indirectly, the IOP.
After many studies using first artificial eyes, then rabbit eyes and
finally human eyes, Grolman had documented that the longer the air jet
was allowed to build up, the larger the area of corneal applanation. Since
he knew how the air pressure increased with time he could use time taken
to reach a standard degree of applanation as a "correlate" to IOP. To do
that however, required much data gathering with his instrument and a Goldmann
on human subjects to develop a table to convert time required to reach
applanation into measurements of IOP. Later, the final instrument would
make this conversion electrically and display the IOP in an illuminated,
digital readout display.
Other advantages to this method then became apparent. Unlike a Goldmann
tonometer that contacts the cornea for several seconds (and moves while
in contact) the air pulse lasted only 3-5 milliseconds so if a patient
began to blink at the sound of the instrument "firing', the measurement
was done before the eye lid could descend.
Only air "touched" the eye which removed the risk of ocular infection
possible with mechanical tonometry and studies found the brief air applanation
was so non-traumatic an eye could be measured a hundred times without detectable
aqueous message (lowering of successive IOP readings) or the significant
corneal staining often produced by Goldmann.
Since no corneal anesthetic was needed this technique would be Grolman's
response to those radio spots and open the door for rapid, routine and
accurate IOP measurements by optometrists. Or anyone else for that matter
since it took but minutes of training to use the prototype.
What remained for Grolman was to determine the time it took for the
air pulse to applanate the cornea and correlate those times with IOPs.
Grolman fitted the prototype with a narrow infrared (IR) beam angled
that reflected off the corneal and was sensed by an IR detector on the
opposite side of the cornea. When the corneal apex was spherical it scattered
the IR beam in all directions but, as the air pulse flattened the apex,
it increasingly reflected more of the IR beam into the detector. The more
applanation, the higher the IR detector read and Grolman had a way to determine
the degree of applanation with the time taken by the air pulse to produce
that applanation and had the key pieces in place.
He next discovered that beyond a certain time the corneal apex began
to become concave, causing the intensity of the reflected IR beam to decreased
rapidly while after the air pulse ended the cornea recovered another peak
of reflected IR light was detected at a second applanation with the cornea
rebounding. The time when the IR detector first read maximum was then correlated
with IOP.
Grolman had devised an air pulse that:
o Increased in a known, repeatable manner.
o Flattened the corneal and caused the reflected IR beam to peak at applanation.
This meant applanation occurred when the reflected IR beam reached maximum
so his technique measured not air pressure at applanation but time taken
to reach applanation. Grolman had a correlate of IOP ---time taken to reach
applanation--- different from the one used by Goldmann---force used to
reach applanation---so Grolman had only to calibrated time to applanation
vs IOP just as Goldmann had calibrated force used to reach applanation
vs IOP.
Much work remained to produce a practical instrument of course. Grolman
had to devise an optical alignment system to accurately place the air nozzle
on the corneal axis a set distance away, a patient fixation target and
develop measuring circuits to detect the time taken to reach applanation.
Then measure many subjects with Goldmann and the prototype NCT over a wide
range of IOPs to develop the time v IOP correlation, document if the air
pulse harmed the cornea (glass particles bounced harmlessly off rabbit
corneas) and whether corneal astigmatism affected the instrument.
It was after about 10 years that the new tonometer--a non-contact tonometer
(NCT)--- was introduced late in 1971 at the Annual meeting of the American
Academy of Optometry in Toronto and later at the World Optical Fair in
the spring of 1972.
Early in 1973, the AO Non-Contact tonometer appeared in our clinic.
Seeing it operate was a revelation. After a few minutes training anyone
could measure IOP in both eyes, several times, in under a minute. No anesthetic
was needed and there was no risk of infection or trauma to the cornea.
A faculty member, Dr. Witenberg, conducted a study that found the optimal
technique was to use the median of three successive readings.
The AO NCT was rapidly accepted and flourished although AO changed ownership
several times and the instrument is now in its 4th generation.
The first version was followed by the NCT II (revised electronics) and
then the Reichert and Lecia Xpert tonometer series. The most recent Xpert
version does not require a chin rest, automatically aligns to the patient's
cornea, and has a less powerful and quieter air pulse whose pressure and
all models of the NCT are found through out the world.
But inter-professional politics affected how the NCT was initially viewed
in some quarters and would not have occurred had the instrument been introduced
today.
The NCT came out while the first efforts were being made by optometry
to update obsolete optometry laws. Those ophthalmologists opposed to these
changes viewed Goldmann tonometry as one thing that distanced them from
optometrists--- the radio spots Grolman heard were one example and, human
nature being what it is, some ophthalmologists questioned whether the NCT
was accurate.
Soon a German ophthalmologist published an early review that incorrectly
alleged the NCT was less accurate than a Goldmann (at higher pressures)
and this was believed by some ophthalmologists and optometrists.
That sole claim was refuted by many studies over the last 30 years but
is still occasionally believed, I regret to say, by some although all NCT
models meet the ISO tonometer requirements.
As accurate as the Goldmann, the NCT however:
o Does not depend upon operator skill or subjective criteria.
o Poses no risk of infection.
o Automatically checks calibration at start-up.
o Provides a printed record of IOP.
o Activates a "low confidence" light when internal parameters are non-optimal.
o Lends itself to rapid, mass IOP screenings
But even today if an NCT reads a high pressure a repeat measurement
with the Goldmann is sometimes done to "verify" the NCT reading when, in
truth, the NCT can, as logically, "verify" a Goldmann reading since there
are more factors that can adversely affect a Goldmann than an NCT.
This is not to denigrate the Goldmann. It remains, an excellent instrument
and was a great improvement on the Schiotz, an instrument requiring even
more skill and even more open to cornea trauma and spread of infection.
And today most clinicians have NCT and Goldman tonometers and use both.
Dr. Grolman held 45 US patents and developed other ophthalmic instruments
besides the NCT and served as Chief Scientist at his company for 18 years
before "retiring" in 1985 but remained an active consultant and was awarded
honorary doctoral degrees by the Illinois College of Optometry and the
New England College of Optometry and, in 1990, the William Feinbloom Award
from the American Academy of Optometry.
Dr. Grolman was in Buffalo, NY last month when he was stuck and killed
by a car. He had been working that day with his colleague Dr. David Luce
on forthcoming clinical trials of a new NCT. He was preceded in death by
his loving wife and is survived by 5 children and multiple grandchildren
who mourn his passing.
I knew Bernie for 30 years and will remember his inventive genius, kindness
and "old school" manners. No one who knew him failed to respect and like
him.
And for all of us who use NCTs in our daily practice…Thank You Dr. Grolman.