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Say ‘no’ to crummy tonometry
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To the Editor:
After reading comments from Derek MacDonald, OD, FAAO, on the corneal biomechanics/tonometry study (“Corneal biomechanics explain variability in results with different tonometers,” June 2018, page 19) and debating about writing a response, I gave in to my instincts.
When I worked with Ziemer, we had an expression written by my old friend and colleague, Tony Wirthlin, PhD, who passed away a few years ago: “Since IOP is the only modifiable variable, why not try to measure it as accurately as possible?”
Your comments would have some merit in a perfect world where patients stay with the same doctor for many years, where baseline optic nerve OCTs and threshold fields are always on board to allow us to reliably monitor nerve fiber loss. In that world, accurate IOP measurement might not matter as much.
Consider this: 3 million Americans have glaucoma; only half of them know it; 15 million Americans have had LASIK, and only dynamic contour tonometry (DCT, Pascale, Ziemer) and Ocular Response Analyzer (ORA, Reichert) work reliably on them; false negative IOP measurements during a routine exam delays a glaucoma work-up, hence, IOP risk-related glaucoma remains undiscovered; and failure to diagnose glaucoma is the No. 1 cause for optometric malpractice.
We need the very best tools available to screen for suspects. With more precise IOP screening, suspects are more likely to receive a baseline work-up. If a patient with 27 mm Hg IOP is perceived to have only 17 mm Hg, their work-up is most likely to be delayed. Our ability to diagnose and manage promptly will improve with better tonometry. The science is out there. There are tonometers capable of reading 17 mm Hg with real IOP being over 27 mm Hg. Goldmann tonometry was brilliant in 1952. Today, it is outdated and highly outclassed by DCT and ORA.
This study was significant because it has reiterated our previous scientific understanding that individual variability in corneal properties helps explain the flaws in most tonometers. It begs for the common sense that the ophthalmic industry owes both us and those we serve precise tonometry. It would make an important difference, and it is about time that we stop kicking this important can down the road. When we casually accept inferior and outdated technology in our profession, we abandon our mission to seek a higher standard for our patients. Please, just say “no” to crummy tonometry!
Elliot M. Kirstein OD, FAAO
Director, Harper’s Point Eye Associates, Ohio
Disclosure: Kirstein reports he is on the speakers’ alliance for Alcon, Haag-Streit, Optovue and Reichert. He has served as a consultant for Paradigm Medical Industries and Ziemer Ophthalmology.
Let me begin by thanking Dr. Kirstein for, and confirming my agreement with, his insightful comments regarding the importance (and current absence) of accurate and repeatable IOP measurement.
Goldmann applanation tonometry, akin to Snellen acuity, remains the reference standard in clinical practice largely by virtue of longevity, not superiority. Alternatives with definite advantages exist but, for a number of reasons, have yet to gain widespread traction in the trenches.
In my utopian world of lifelong doctor-patient relationships, a better understanding of corneal biomechanics would be an invaluable support to clinical decision-making. In the real world — where such relationships are the exception to the rule – the ability to share or transfer care with a more objective understanding of IOP (and while we’re at it, of retinal nerve fiber layer and ganglion cell thickness, given segmentation algorithm variability between instruments) would be equally invaluable.
Inarguably, glaucoma is underdiagnosed. Part of that problem arises from asymptomatic individuals not seeking eye care; however, a failure to recognize risk factors (elevated IOP being one among many) or signs of early manifest disease in those who do is also a significant concern.
To these ends, improving our ability to diagnose and individually and collaboratively manage patients with glaucoma is of paramount importance. It’s also eminently achievable but will require the reconciliation of technological advancement with fiscal reality and, critically, a commitment to stay vigilant and continually upgrade the ultimate clinical decision-maker: the person reading these words.
Derek MacDonald, OD, FAAO
Private practitioner, Waterloo, Canada
Member, Optometric Glaucoma Society
Disclosure: MacDonald reports no relevant financial disclosures.