In the JournalsPerspective

Smartphone tonometer provides reliable preliminary IOP

Calculating preliminary IOP using a smartphone-based tonometer yielded similar results compared with other tonometers, according to findings published in the British Journal of Ophthalmology.

Yue Wu and colleagues compared IOP measurements taken with a prototype smartphone tonometer with other tonometers used in clinical practice.

“As smartphones have become increasingly ubiquitous, a number of software programs and hardware attachments have been developed to allow a smartphone to perform various parts of the eye examination,” Wu, a graduate student at the University of Washington, and colleagues wrote. “Smartphone-based methods for measuring visual acuity have been validated.”

The researchers analyzed data from 92 eyes in 81 academic glaucoma patients. Measurements taken by Goldmann applanation tonometry (GAT) as well as ICare, pneumotonometry and Tono-Pen (Reichert) were compared.

The mean difference in IOP measurements was 0.24 mm Hg for GAT, -1.39 mm Hg for ICare, -3.71 mm Hg for pneumonotomy and -1.30 mm Hg for Tono-Pen, according to the study. The 95% limits of agreement were -4.35 mm Hg to 4.83 mm Hg for GAT, -6.48 mm Hg to 3.70 mm Hg for ICare, -7.66 mm Hg to -0.15 mm Hg for pneumotonometry and -5.72 mm Hg to 3.12 mm Hg for Tono-Pen.

The smartphone tonometer results were most consistent with GAT (R2 = 0.67; P < .001). Of the videos of the 92 eyes, 97.8% were within ±5 mm Hg of GAT, and 63% were within ±2 mm Hg of GAT, the authors wrote.

“A smartphone-based tonometer complements other existing smartphone hardware attachments and apps to facilitate a portable ophthalmological examination, which may improve access to ophthalmological care in resource-poor regions,” Wu and colleagues concluded. – by Earl Holland Jr.

Calculating preliminary IOP using a smartphone-based tonometer yielded similar results compared with other tonometers, according to findings published in the British Journal of Ophthalmology.

Yue Wu and colleagues compared IOP measurements taken with a prototype smartphone tonometer with other tonometers used in clinical practice.

“As smartphones have become increasingly ubiquitous, a number of software programs and hardware attachments have been developed to allow a smartphone to perform various parts of the eye examination,” Wu, a graduate student at the University of Washington, and colleagues wrote. “Smartphone-based methods for measuring visual acuity have been validated.”

The researchers analyzed data from 92 eyes in 81 academic glaucoma patients. Measurements taken by Goldmann applanation tonometry (GAT) as well as ICare, pneumotonometry and Tono-Pen (Reichert) were compared.

The mean difference in IOP measurements was 0.24 mm Hg for GAT, -1.39 mm Hg for ICare, -3.71 mm Hg for pneumonotomy and -1.30 mm Hg for Tono-Pen, according to the study. The 95% limits of agreement were -4.35 mm Hg to 4.83 mm Hg for GAT, -6.48 mm Hg to 3.70 mm Hg for ICare, -7.66 mm Hg to -0.15 mm Hg for pneumotonometry and -5.72 mm Hg to 3.12 mm Hg for Tono-Pen.

The smartphone tonometer results were most consistent with GAT (R2 = 0.67; P < .001). Of the videos of the 92 eyes, 97.8% were within ±5 mm Hg of GAT, and 63% were within ±2 mm Hg of GAT, the authors wrote.

“A smartphone-based tonometer complements other existing smartphone hardware attachments and apps to facilitate a portable ophthalmological examination, which may improve access to ophthalmological care in resource-poor regions,” Wu and colleagues concluded. – by Earl Holland Jr.

    Perspective
    Brad Sutton

    Brad Sutton

    As if there are not enough uses for smartphones already, how about adding measuring IOP to the list? This proof-of-concept study set out to determine if it would be feasible to create a prototype smartphone-based device with a machine learning computer algorithm capable of measuring IOP. After reading the report, I think the jury is definitely still out. The IOP obtained by the device did correlate well with Goldman IOP, differing by only + 0.24 mm Hg on average, but this comes with many caveats.

    The instrument applanates the cornea after the patient has been supine for 5 minutes, then analyzes video of this applanation to calculate IOP. Out of 162 eyes on which videos were obtained, there were only 92 eyes with acceptable data that allowed IOP calculation (56.8%). Clearly, that would need to drastically improve. In addition, supine IOP is known to be higher than seated IOP, so the researchers subtracted 4.1 mm Hg from the smartphone IOP readings to calculate the comparison to Goldman IOP. While that may be an accurate adjustment on average, it may not effectively apply to many individuals.

    Overall, one of the biggest questions for me is: What would we gain if this technology came to fruition? Would patients be able to take their own IOP at home with their smartphone? Maybe, but not with just their smartphone. They would need the applanating attachment to connect to their phone, and they would need Fluress (fluorescein sodium, benoxinate HCL ophthalmic solution, Akorn). Would we as practitioners have a portable way to measure IOP in out-of-office settings? Yes, but we have several devices for doing that already, such as ICare, Tono-Pen and Perkins (Haag-Streit).

    • Brad Sutton, OD, FAAO
    • Clinical professor, Indiana University School of Optometry
      Service chief, Indianapolis Eye Care Center

    Disclosures: Wu reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.