Dr. Downs believes the latest data calls into question the validity of most of the work that’s been done on IOP fluctuation, whether the fluctuation is diurnal or over the long term. “I don’t think we really have any idea how human IOP fluctuates,” he says. “That might explain why the data from some of the big studies suggest a link between long-term IOP fluctuation and glaucomatous progression while other studies don’t show a connection. These data are generally based on measurements taken once every three to six months. Our data suggest that snapshots taken months apart tell us very little about what’s really happening to the patient’s IOP.
I agree that the mainstream glaucoma community lacks sufficient understanding in this area.
However, any of you who own a tonometer and perform home eye pressure monitoring according to the FitEyes protocol (using the FitEyes Insight software) can quickly come to have a deep understanding of how your IOP fluctuates.
I believe the very best data on how human eye pressure fluctuates comes from the real life home IOP data collected by FitEyes members who have tonometers.
As a group, FitEyes members have pioneered the recognition that IOP fluctuates in response to almost every psychological and emotional state humans experience. In the article below I comment on just how powerful these psychological and emotional factors are in the equation of IOP fluctuation.
Stress and Eye Pressure - Solving The Equation | FitEyes.com
Notice the parallels between what FitEyes members have observed and the quote by Bioengineer Dr. Crawford Downs, research director of the Ocular Biomechanics Laboratory at Devers Eye Institute in Portland, Ore.:
“For example, if I walk into the room and an animal doesn’t know me very well, his IOP may go from 11 to 55 mmHg,” Dr. Downs says. “Every time our animals blink, their IOP goes up about 10 mmHg; every time they move their eyes—standard saccadic movements like those we all make all day, every day—IOP goes up 4 or 5 mmHg. We also have IOP data taken during Tonopen measurements of the animals’ pressure [which require touching the eye]. Those measurements, performed by Dr. Burgoyne, generated IOP spikes 12 to 25 mmHg above baseline. Furthermore, any time we turn the lights off, or there’s a loud noise, the animals’ IOP spikes—which means that outside stressors or environmental factors really affect the animals’ IOP. We videoed the animals during these events, and they were not rubbing their eyes or squinting or doing anything else that would cause these pressure spikes.”
Dr. Downs says that overall, the amount of IOP variation they are finding is striking. “At 2:00 p.m. an animal could be at 11 mmHg; at 3:00 he’s at 17 mmHg,” he notes. “In any 24-hour period the swing was over a 15-mmHg range—and that’s after averaging out the high-frequency fluctuations, which can be huge.”
Dr. Downs notes that he and Dr. Burgoyne were not expecting these findings. “For years Dr. Burgoyne assumed that he was getting a reasonable estimate of an animal’s IOP by measuring pressure once a week using applanation tonometry,” he says. “Based on our recent data, we are coming to believe that this may be inadequate. Although snapshot tonometry remains the best way to characterize IOP noninvasively, at this point I don’t think we really understand what’s going on with IOP in either primates or humans. At the least, these data suggest that getting a meaningful idea of a patient’s IOP by measuring it in the clinic once every three or six months is impossible.”
Home IOP monitoring is currently the only viable solution. Every glaucoma patient needs to be taking advantage of this.
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