Optometric Management Tip # 132 - Wednesday, July 28, 2004
Non-contact tonometers... they get no respect
There are a few topics that optometrists are pretty divided on, even passionate about, and air puff tonometry is one of
those. Lots of ODs use non-contact tonometers (NCT) on a daily basis in practice, but a huge segment thinks the devices
are not worthy. I’m in the camp that thinks they have a lot of value, so much so that I’ll present the topic as a tip
worth considering to colleagues who don’t have one. I think NCTs have received an undeserved bad rap in many circles.
I’ve heard them referred to as boat anchors. I say take another look at them.
First, let me acknowledge that Goldmann applanation is the standard that all tonometers are compared with, and it is the
preferred instrument to diagnose and treat glaucoma with. All my exam rooms are equipped with applanation tonometers on
the slit lamp, and we perform the test many times per day. But there is a big advantage to delegating routine tonometry
to qualified technicians as a pre-test, and NCT is the easiest way to do that. NCTs are not intended to replace Goldmann
in a practice, but to be used with Goldmann.
Here are some common myths about air puff tonometers. See if you believed any of these, and see if I can change your mind.
- The NCT is just a screener. We can call it a screener if you like, but in my experience, it’s a very accurate one.
And for many patients, that’s all I need. Many patients are in for routine exams, and we’ve been seeing them for years.
Many have small cups, low IOPs and perfect visual field screenings. Many are contact lens wearers under age 30. While we
obviously need to check IOP at every exam, NCT vs Goldmann doesn’t matter in these patients. If a patient has risk factors,
such as a large C/D ratio or family history, you can always do Goldmann, and then you have two measurements for more data.
- The NCT is not accurate. I’ve actually found them to be quite accurate, especially the newer models. I’ve had 4 NCTs
over the years. Two that I’d call “first generation” and my two present identical machines, used in our two pre-test rooms.
I’ve compared IOP measurements from these NCTs with Goldmann readings on thousands of patients, and they are consistently
within 1-2 mms. If the NCT reads high, I know we have a problem that demands further testing. Even my old NCTs were
accurate and repeatable… if anything, they read a few mms higher than Goldmann, which only caused me to re-test with
applantation more often. As a side note, I also have a Tonopen, which we like and find very useful, but it has much more
inconsistency and does not relate to Goldmann as well as NCT. Yet, Tonopen seems to enjoy more respect than NCT.
- Patients hate the dreaded air puff. Well, they used to, and many still think they do because they’ve only had the early
version of the instrument. But today’s NCTs are very different. For several years now, NCT instruments from several
manufacturers have had very gentle, soft puffs of air. My patients are delighted with it, and we have a good laugh about
how strong the old puffs used to be and how much better the new generation is. Newer NCTs are also much quieter -- the
loud clunk noise was half the problem before. My staff performs air puff easily on three year olds (compare that to
Goldmann). We reassure nervous patients that the new puff machines are vastly better, and they always end up happily
agreeing after they’ve had it – they easily sit for two or three readings on each eye. Have NCT done on your own eye at
the next convention – there is nothing to it anymore. We should acknowledge that Goldmann tonometry is not universally
loved by the public either; many patients are not thrilled with the drops and the sticky orange dye, and some are sensitive
to being touched with the instrument.
- It doesn’t take that long to just do Goldmann. True, but it does take a few minutes (drops and all), and if you see 15
patients per day, that can add up to over an hour per day. If that extra time would let me see two or three more patients
per day… well, you do the math. Also, fluorescein/benoxinate gets messy with soft contacts, and no disinfection of the
tonometer tip is needed.
- Techs can be trained to do Goldmann. True, and some of my technicians do Goldmann in my practice. But, with multiple
staff, varying skill levels and staff turnover, NCT is the easiest, safest and most reliable for most techs to perform,
because it is automated and computer-verified. Our NCT instruments actually seek and find the corneal reflex
automatically – they are self-aligning and then fire automatically! Just get it in the general area and push the go button.
- NCTs are expensive, and I already have a Goldmann. NCTs are sort of middle of the road, as cost goes – not cheap, but
not that expensive. The important point is the efficiency that arises from delegation is a very valuable thing. You’ll
make up the cost in no time.
Best wishes for continued success,
Neil B. Gailmard, OD, MBA, FAAO
Chief Optometric Editor, Optometric Management