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Presenter: Monocular drug trial does not work
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SEATTLE – A speaker here at the Optometric Glaucoma Society annual meeting reported that treating glaucoma only in one eye to determine if the therapeutic will be effective will not produce reliable results.
Tony Realini, MD, MPH, at the meeting held just prior to the American Academy of Optometry annual meeting, presented his own research as well as data from published studies to prove his point.
“To make the monocular drug trial work, you assume the IOP fluctuates in symmetry between the two eyes,” Realini said. “This is not true. Spontaneous IOP fluctuations that occur in normals and in those treated are frequent. It could mimic or mask a positive monocular drug trial.”
He said it is often assumed that the diurnal curve is reproducible over time. Realini shared the results of a trial he conducted of 50 patients without glaucoma. Patients were evaluated 5 days over the course of a year, with their pressure checked every 2 hours over 12-hour periods.
“Does the diurnal curve change?” he said. “It doesn’t bear any resemblance to itself from the start. That’s disconcerting. The exact same is true in glaucoma patients. You do a diurnal curve today and it has nothing to do with the diurnal curve tomorrow.”
Several other common assumptions have been disproven, he said.
Many mistakenly believe ocular agents have no crossover effect.
Another unproven assumption is that both eyes respond similarly to the same medication, he added.
And the last common misconception is that patients use their drops as prescribed.
The better question to ask, Realini said, is whether the IOP reduction in the first eye can predict the IOP reduction in the other eye.
In his own study, he took three IOP measurements prior to treatment and three after treatment in a group of patients over 6 months and found that the IOP reduction in one eye did not predict IOP reduction long-term.
“The real question is: What is the optimal time and frequency of IOP measurements to characterize an individual’s therapeutic response to an IOP-lowering drug?” Realini asked. “I am now studying this and should have the data in about 6 months.”
As part of his take-home message, Realini stressed that glaucoma is a slowly progressing disease.
“Give your medication time to show you that it’s working,” he said.