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This month, News in Review highlights selected papers from the original papers sessions at AAO 2022. Each was chosen by the session chairs prior to the meeting because it presents important news or illustrates a trend in the field. Only three subspecialties are included here; papers sessions also were held in six other fields.
THE COVID-19 pandemic sparked a re-evaluation of the iCare tonometer, a handheld portable device that measures IOP without topical anesthetic and minimizes eye surface contact. In light of the possibility that iCare might also minimize viral transmission, researchers at Wills Eye Hospital in Philadelphia evaluated the tonometer’s accuracy by comparing it to the gold standard, Goldmann applanation tonometry (GAT).1
The researchers “did this study to investigate if iCare is an accurate method to measure IOP in the midst of COVID-19—and if it truly could be a substitute for GAT,” said Shreya Swaminathan, BS, at Sidney Kimmel Medical College. Both devices touch the surface of the eye, although iCare’s diameter is smaller.
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IN PURSUIT OF ACCURACY. How should IOP be measured? Although GAT (shown here) is considered the gold standard, the iCare tonometer may also be used.
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A retrospective assessment. For this retrospective cohort study, the researchers considered clinical data from 350 patients (700 eyes) seen between March 2020 and March 2021. They chose 350 right eyes for final analysis, repeating the analysis in the left eye for verification.
Initially, IOP was measured by ophthalmic technicians using iCare. Repeat measurements were performed within 90 minutes by a glaucoma specialist using GAT. Primary outcome measures included the correlation between iCare and GAT IOP readings and factors influencing the differences in those readings.
IOP correlation. IOP readings from both tonometers showed high levels of correlation, with an intraclass correlation coefficient (ICC) of .899. Bland-Altman plots indicated a 95% limit of agreement between –5.8 to 5.5 mm Hg, suggesting the devices are not interchangeable for measuring IOP. This trend was consistent in eyes with IOPs both above and below 21 mm Hg.
Additional results. Other findings included the following:
- Greater central corneal thickness (CCT) was significantly associated with increased divergence in IOP measurements obtained with the two approaches.
- For each decade of increase in age, the IOP reading was .4 mm Hg lower with iCare than with GAT.
- Greater variation between the two tonometers was noted at higher IOP ranges. Specifically, there were significantly more patients with an IOP difference greater than 3 mm Hg among those with IOP ≥21 mm Hg than among those with IOP ≤21 mm Hg.
- Factors not associated with differences in IOP measurements achieved with the two approaches included prior glaucoma surgery, mean retinal nerve fiber layer thickness, axial length, and factors involving the technicians (i.e., years of practice and level of certification).
A caution: not interchangeable. Despite the high intraclass correlation between the two devices, they cannot be used interchangeably, Ms. Swaminathan said. “The fact that more than 20% of patients had a difference of IOP readings greater than 3 mm Hg is striking and indicates that although iCare is close most of the time, it may not be an appropriate substitute for all patients,” she commented.
What’s next? Ms. Swaminathan stressed that further research needs to be done to find a method of measuring IOP that is both accurate and carries a low risk for viral transmission. “While iCare may not be completely accurate when it comes to IOP measurement, it may provide a clinical picture in an environment in which virus transmission is a large concern.”
—Miriam Karmel
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1 Swaminathan S et al. A comparison of iCare and Goldmann applanation tonometry measurements during the COVID-19 pandemic: a retrospective study. Paper presented at: AAO 2022; Oct. 3, 2022; Chicago.
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Relevant financial disclosures—Ms. Swaminathan: None.
For full disclosures and the disclosure key, see below.
Full Financial Disclosures
Dr. Khanani Adverum: C,S; Alkahest: S; Allergan: C,L,S; Gemini: C,S; Genentech: C,S; Graybug: C,S; Gyroscope: C,S; Iveric Bio: C,S; Kato Pharmaceuticals: C; Kodiak Sciences: C,S; Neurotech: S; NGM Pharmaceuticals: S; Novartis: C,L,S; Opthea: C,S; Oxurion: C,S; Polyphotonix: C; Recens Medical: C,S; Regenxbio: C,S.
Dr. Mamalis Alcon: S; Anew Optics: C,S; Atia Vision: S; Carl Zeiss: S; ClarVista: S; Cristalens: S; Hoya: S; LensGen: S; Long Bridge Medical S; Medicontur: S; Merck: S; Ocumetrics: S; PerfectLens: C,S; Spyglass: S.
Ms. Swaminathan None.
Dr. Werner Adaptilens: S; Alcon: C,S; Anew Optics: S; Bausch + Lomb: C,S; Carl Zeiss: S; Cristalens: S; Hoya: C,S; HumanOptics: S; LensGen: S; Long Bridge Medical: S; Mediphacos: S; Ocumetrics: S; PerfectLens: S; Shifamed/Atia: S; Spyglass: S.
Disclosure Category
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Code
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Description
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Consultant/Advisor |
C |
Consultant fee, paid advisory boards, or fees for attending a meeting. |
Employee |
E |
Hired to work for compensation or received a W2 from a company. |
Employee, executive role |
EE |
Hired to work in an executive role for compensation or received a W2 from a company. |
Owner of company |
EO |
Ownership or controlling interest in a company, other than stock. |
Independent contractor |
I |
Contracted work, including contracted research. |
Lecture fees/Speakers bureau |
L |
Lecture fees or honoraria, travel fees or reimbursements when speaking at the invitation of a commercial company. |
Patents/Royalty |
P |
Beneficiary of patents and/or royalties for intellectual property. |
Equity/Stock/Stock options holder, private corporation |
PS |
Equity ownership, stock and/or stock options in privately owned firms, excluding mutual funds. |
Grant support |
S |
Grant support or other financial support from all sources, including research support from government agencies (e.g., NIH), foundations, device manufacturers, and\or pharmaceutical companies. Research funding should be disclosed by the principal or named investigator even if your institution receives the grant and manages the funds. |
Stock options, public or private corporation |
SO |
Stock options in a public or private company. |
Equity/Stock holder, public corporation |
US |
Equity ownership or stock in publicly traded firms, excluding mutual funds (listed on the stock exchange). |
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