Reliability of Intraocular Pressure Measurements in a Low-Contact Drive-Through Setting

Précis: Drive-through intraocular pressure (IOP) measurement using iCare tonometry is a promising method of low-contact, high-throughput IOP monitoring. However, owing to its vulnerability to variable measurement technique and local air currents, the iCare may overestimate IOPs. Purpose: During the COVID-19 pandemic, a drive-through IOP measurement protocol using the iCare tonometer was established to facilitate low-contact monitoring of select glaucoma patients. As the iCare may be prone to error due to variable measurement technique and local air currents, we endeavored to assess the reliability of drive-through IOP measurements by comparing them with recent measurements taken in clinic settings. Methods: Inclusion criteria were patients with drive-through IOP measurements performed from April 28 to October 11, 2020; exclusion criteria were pre-drive-through IOPs >21 mmHg. Drive-through IOP measurements were compared with the closest previous and/or subsequent in-clinic IOP measurements. Data were gathered using the Sight Outcomes Research Collaborative (SOURCE) data repository. Results: The post-exclusion study group consisted of 314 patients receiving a total of 868 drive-through IOP measurements, all of whom had prior in-clinic measurements, and 56.8% of whom had subsequent in-clinic measurements. Drive-through IOPs were, on average, +2.4 mmHg (+14.5%; SD 4.9) higher than in-clinic IOPs. Further sub-analysis of the data showed a difference of +2.1 mmHg OD and +2.6 mmHg OS. Compared with the closest previous in-clinic visit, the difference was +2.4 mmHg OU (+2.1 mmHg OD, +2.7 mmHg OS); compared with the closest subsequent in-clinic visit, the difference was +2.3 mmHg OU (+2.1 mmHg OD, +2.5 mmHg OS). 68.6% of all drive-through IOPs were higher than corresponding in-clinic IOPs; 21.1% were lower. 25.9% of drive-through IOPs were higher by more than 5 mmHg, whereas 3.9% of drive-through IOPs were lower by more than 5 mmHg. Discussion: As teleophthalmology becomes an ever more important tool in glaucoma patient care, drive-through or walk-through IOP monitoring methods are likely to play an increasing role. However, our data reveals potential inaccuracies in drive-through iCare IOP measurements which tended to overestimate IOP. It is advisable to confirm large changes in IOP with in-clinic measurement before making management decisions. Conclusion: With better optimization of accuracy and reliability of measurements, drive-through tonometry is a promising, high-throughput, low-contact method of measuring IOP.