IOP fluctuation a critical but often underestimated glaucoma parameter

NAPLES, Italy — IOP fluctuation in glaucoma patients is an important parameter that is often neglected or underestimated, according to a specialist speaking here.

"Circadian fluctuations occur in normal and glaucomatous eyes, but a great deal remains unknown due to a lack of noninvasive methods of continuous measurement of IOP in the patient's own environment," Sanjay Asrani, MD, said at the joint meeting of Ocular Surgery News and the Italian Society of Ophthalmology.

"We measure our patients' IOP for a total of about 5 to 6 seconds in the whole year because we do three or four visits during which we take a measurement for 1 to 2 seconds," he said. "This is a very low amount of data. That doesn't reflect the changes that occur at different times of the day and night, and in relation to the patients' activities, stress and emotional changes."

IOP changes just like blood sugar changes, he said, and the availability of glucose monitoring systems has shown to be important in the management of diabetes.

"Of course it would be great to have an eye pressure monitoring system. Experimental devices, like pressure-monitoring contact lenses and implantable microchips, are currently under investigation, and we hope that in a few years time they'll become available," he said.

In the meantime, Dr. Asrani said, practitioners should measure long-term IOP variations at multiple office visits during daytime clinic hours over a period of several months or take "mini-curves" of diurnal IOP fluctuations.

"Currently, the correlation between variations in blood pressure and IOP are investigated, as well as the impact of the changes in cerebrospinal fluid pressure on the lamina cribrosa and consequently on IOP fluctuation," he said. "There is also increasing evidence that some medications, like diuretics, are correlated with the development of glaucoma."

"What's important to remember is that we don't want the eye pressure to go down and stay low three times in a year. Particularly in our patients with advanced glaucoma, in our patients where the disease continues to progress despite having pressures that seem to be in the low-normal range, we have to realize the importance of fluctuation and must make sure that IOP remains constantly low, with as little fluctuation as possible," Dr. Asrani said.