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More IOP fluctuations found in medically than surgically treated eyes
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Nocturnal IOP-related fluctuations are significantly more pronounced in medically treated than in surgically treated glaucoma, according to a study.
Continuous IOP-related values were obtained by fitting 91 eyes of 77 glaucoma patients with the Sensimed Triggerfish contact lens sensor, a soft contact lens capable of registering changes in corneal curvature and ocular volume that may reflect changes in IOP. Fifty-nine eyes were receiving glaucoma medications, while 32 had previously undergone glaucoma surgery with a variety of methods.
After 24 hours, the lenses were removed, and the data were analyzed, showing a higher amplitude of ocular volume changes in the medical than in the surgical group. The maximum (acrophase) and minimum (bathyphase) IOP-related values were higher in the medical than in the surgical group, and an absence of nocturnal acrophase was found in 42.9% of surgically treated vs. 13.8% of medically treated eyes.
These results, according to the authors, suggest that surgery might result in better 24-hour IOP control and less IOP fluctuation than medications, even when mean IOP, as measured by applanation tonometry, appears to be similar.
The role of IOP fluctuations as an independent risk factor for glaucoma progression has been shown in several studies, the authors noted. They emphasized the importance of monitoring IOP changes over 24 hours, and particularly at night, rather than relying on a single 1- or 2-second snapshot taken in the sitting position in the office.
“In line with previous reports, our study confirmed the ability of the Sensimed Triggerfish sensor to describe the circadian IOP-related profile. Even though several studies have clearly shown that the highest IOP values occur at night in most cases, clinical management of glaucoma is based on a single IOP measurement, usually taken during hospital outpatient hours,” they wrote. – by Michela Cimberle
Disclosure: The authors reported no relevant financial disclosures.
Perspective
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Mark Eltis, OD, FAAO
Elevated IOP is a strong risk factor for glaucoma, and prospective, randomized clinical trials have left little doubt that its reduction delays or prevents disease onset and progression. Not having been studied prospectively, the role of IOP fluctuation is decidedly less certain – and more contentious. However, recently developed technology allows IOP measurements over a 24-hour cycle to address this question.
Muniesa Royo and colleagues used a contact lens sensor to compare IOP fluctuations and prevalence of nighttime spikes. Not surprisingly, surgically treated patients had fewer IOP fluctuations and nighttime spikes.
Although I’m concerned that the level of patient adherence with medications was not monitored (potentially giving surgical patients an artificial advantage), this study invites us to reevaluate both our diagnostic and treatment methods. It is a reminder of the limitations of applanation tonometry in detection and management of glaucoma and also suggests we may need to rethink our treatments. For example, patients progressing despite “good” IOP control may be better served by surgical intervention earlier in the disease process. Of course, careful monitoring over time and appropriate treatment adjustments will ultimately determine which patients need tighter IOP control.
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