Drive-thru IOP monitoring may yield inaccurate results, overestimate IOP
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Key takeaways:
- More than two-thirds of all drive-thru IOPs were higher than in-clinic measurements, and 21.1% were lower.
- Drive-thru IOP measurements were higher on average by 2.4 mm Hg.
Though “promising” as a low-contact form of IOP monitoring, drive-thru measurement using iCare tonometry may overestimate IOP, and significant changes should be confirmed in a clinic, according to research published in Journal of Glaucoma.
“Telemedicine has played an increasingly prominent role in ophthalmology in recent years, and the COVID-19 pandemic and subsequent limitations on in-person care has provided an unprecedented drive toward virtual health care models,” Lynn W. Sun, MD, PhD, and colleagues at the University of Michigan Kellogg Eye Center, wrote. “At our institution, drive-thru IOP measurement using the handheld iCare rebound tonometer was established early in the pandemic to facilitate safe, minimal-contact monitoring of glaucoma and glaucoma suspect patients.”
Using the Sight Outcomes Research Collaborative data repository, the researchers compared IOP measurements performed with iCare tonometry via drive-thru from April 28 to Oct. 11, 2020, with the closest previous and/or subsequent in-clinic measurements.
The study group included 314 participants and yielded 868 IOP measurements. All participants had previous in-clinic measurements, and 56.8% had subsequent in-clinic measurements.
The researchers found that 68.6% of all drive-thru IOP measurements were higher than in-clinic measurements, while 21.1% were lower. In addition, 25.9% of drive-thru measurements were higher by more than 5 mm Hg, and 3.9% were lower by more than 5 mm Hg.
On average, drive-thru IOP measurements were higher than in-clinic measurements by 2.4 mm Hg.
“Drive-thru tonometry is a promising, low-contact method of safely measuring IOP and will likely remain an important part of teleophthalmology,” Sun and colleagues wrote. “To optimize low-contact IOP monitoring, steps may need to be taken to improve accuracy of such tonometry, whether by modifying measurement protocols, locations or devices.”
They added, “With some changes, reliability and accuracy of measurements can be optimized, and drive-thru IOP checks can become a useful, convenient, high-throughput method of IOP monitoring.”
Perspective
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While applanation tonometry remains the gold standard in IOP measurement, the use of iCare has been an effective screening tool. iCare combines an anesthetic-free procedure with a more comfortable experience than noncontact tonometry.
However, iCare technology is prone to error, due to variation in the angle of the instrument and the distance between the eye and equipment. When the test is performed outdoors, air currents become a factor as well.
During COVID, the idea of drive-thru IOP screening, which is easily operated by a technician, was a timely strategy. While this study shows iCare overestimating IOP by a significant amount, one could argue it is safer than underestimation.
To put the numbers into context, 68.6% of all drive-thru IOP measurements were higher than in-clinic measurements, while 21.1% were lower. Moreover, 25.9% of drive-thru measurements were higher by more than 5 mm Hg, while 3.9% were lower by more than 5 mm Hg. Finally, IOP measurements for drive-thru on average were higher than in-clinic measurements by 2.4 mmHg.
iCare technology has great potential for IOP measurement beyond the clinic and even at home. Indoor measurements may decrease variability, and future models may close the accuracy gap with Goldmann tonometry.
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