Ingrid Hein

March 04, 2017

Tracking intraocular pressure for 24-hours using a contact-lens sensor can help physicians predict the speed of vision loss over the subsequent 5 years in patients who have been treated for glaucoma, new research shows.

"With this information, a doctor can modify treatment to prevent future irreversible vision loss from glaucoma," said Carlos Gustavo De Moraes, MD, from the Edward S. Harkness Eye Institute at the Columbia University Medical Center in New York City.

"In just one day, we can obtain information about what has been happening to a patient in the past 5 years," he explained at the American Glaucoma Society 2017 Annual Meeting in Coronado, California.

"This is significant because we know that previous velocity is predictive of future progression," he pointed out. The patient most likely to progress in the next 5 years is the one who has progressed in the previous 5 years.

The collection of data on intraocular pressure has been a challenge for ophthalmologists. Because intraocular pressure varies over time, a single exam can miss abnormally high levels, and it will certainly miss changes at night. Even in sleep labs, hourly readings disrupt sleep, which affects pressure.

With 24-hour monitoring, a wide range of measurements can be assessed, including how fast intraocular pressure increases and the number of peaks in pressure at night, which is "one of the main parameters indicating how a patient is progressing," Dr De Moraes noted.

In their study, he and his colleagues followed 445 patients in 13 countries for up to 5 years.

They used Triggerfish (Sensimed), a 24-hour contact lens sensor monitoring system, to measure parameters of vision loss. The lens was approved by the US Food and Drug Administration just last year, but it has been used for more than 5 years in Europe and elsewhere.

With the data collected, researchers were able to predict speed of vision loss — fast progression or slow progression — in 78% of treated glaucoma patients (area under the curve, 0.798).

"There are many patients who would benefit from continuous intraocular pressure monitoring, especially high-risk patients," said Pratap Challa, MD, from Duke Health in Durham, North Carolina.

The technology would be useful in clinical practice for patients with low-tension, pigmentary, and pseudoexfoliation glaucoma, and for those progressing despite treatment, he explained.

However, "a lot of data will be generated," said Dr Challa, so the utility of the system "will lie in how easily the data can be interpreted."

Increased Testing Frequency, Small Gains

The current limitations of visual field testing were highlighted in another study presented at the meeting, which showed that testing at more frequent intervals yields only small gains in the detection of glaucoma progression.

The study involved 675 patients (1090 eyes) with glaucoma who underwent at least five visual field tests over a period of 2 to 5 years.

With annual testing, it takes 3 years to detect visual field progression, said researcher Zguchai Wu, PhD, from the Royal Victorian Eye and Ear Hospital in Victoria, Australia. When testing was done two or three times a year, time to detection only dropped to 2.5 years.

If increased testing had proportionally decreased detection time, detection would have decreased from 3 to 2 years with twice-yearly testing and to 1 year with thrice-yearly testing, he told Medscape Medical News.

"Semi-annual visual field testing and confirmation of progression through repeat testing in the initial years of follow-up may provide a good compromise for detecting progression in clinical practice, while minimizing the burden on healthcare resources," the researchers conclude.

Dr Wu acknowledged that although he does not have personal experience with contact-lens sensors, the technology "appears to be a promising clinical tool that could provide further insights into variations in the intraocular pressure of an individual, which may not be captured by clinical measurements at one time point."

"As with any new technology, validation and more real-world studies are required to demonstrate it provides information that would substantially improve the clinical management of patients with glaucoma, compared with current practice," Dr Wu explained.

Dr De Moraes is a consultant for Sensimed. Dr Wu has disclosed no relevant financial relationships.

American Glaucoma Society (AGS) 2017 Annual Meeting: Abstracts PA16 and PA18. Presented March 4, 2017.

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