Measuring IOP in morning, evening critical for disease management
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Key takeaways:
- Mean IOP at 9 a.m. was 15.8 ± 3.62 mm Hg, which decreased to 14.3 ± 3.12 mm Hg by 6 p.m.
- There was no significant relationship between IOP at any timepoint and spherical equivalent, age or sleep duration.
As IOP decreases throughout the day, it is essential for clinicians to evaluate both morning and evening values to effectively monitor IOP-related diseases, according to research published in Cureus.
“IOP is a parameter used for the detection, diagnosis and follow-up of ocular pathologies such as glaucoma. However, this parameter fluctuates throughout the day,” Veronica Noya-Padin, MSc, OD, and colleagues at University of Santiago de Compostela wrote. “This means that even if a subject’s IOP is within the normal range (between 10 mm Hg and 21 mm Hg) at a certain time, it could exceed the umbral value of 21 mm Hg when measured at another time of the day. As a result, a subject may appear normotensive when, in fact, they experience ocular hypertension at certain times of the day.”
In a study of 34 participants, 12 men and 22 women, researchers measured IOP at 9 a.m., 12 p.m., 3 p.m. and 6 p.m. Anamnesis, slit-lamp evaluation and refractive status also were performed after the final measurement to ensure the IOP value was not affected by other measurements.
The researchers found significant differences in IOP between timepoints for all but the narrow-angle group. No significant differences were noted in IOP fluctuations in the total sample or based on angle aperture.
Because no significant differences were reported between eyes at the first read, researchers performed statistical analyses only on the right eye of each participant.
According to results, the mean IOP value at 9 a.m. was 15.8 ± 3.62 mm Hg, followed by 15.8 ± 3.41 mm Hg at 12 p.m., 14.4 ± 2.93 mm Hg at 3 p.m. and 14.3 ± 3.12 mm Hg at 6 p.m.
Researchers reported no significant relationships between IOP at any timepoint and spherical equivalent, age or sleep duration.
“Despite the challenges and costs of monitoring IOP throughout the day, the results of this study along with existing literature, emphasize the importance of measuring IOP at different times to grasp its dynamics in each subject fully,” Noya-Padin and colleagues wrote.
Perspective
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While the disease process of glaucoma ultimately affects the integrity of the optic nerve, IOP is the only known modifiable risk factor and subsequently the predominant risk factor for the diagnosis and management of this silent disease. This dynamic variant is known to fluctuate 4 mm Hg to 5 mm Hg in healthy individuals and even more in glaucoma patients, with it thought to be highest at night and in the early morning hours.
In this small study, Noya-Padin and colleagues tested patients at 9 a.m., 12 p.m., 3 p.m. and 6 p.m. and reiterated previously stated findings that IOP fluctuates throughout the day, with their readings being highest in the morning and decreasing as the day goes on.
Gathering more data points is critical in managing normal tension glaucoma and those with unexplained progression, but is realistically beneficial for all of our glaucoma patients. Varying appointment times allows us to better understand individual IOP fluctuations and identify potential peaks. Newer technologies also offer us more opportunity to obtain this once elusive information.
While it can be difficult to shoot a moving target, obtaining more personalized data may allow us to achieve our goal of minimizing progression of this sight-threatening disease.
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