Nocturnal, sleeping IOP keeps ophthalmologists up at night

There is much to be learned about nocturnal-and, more importantly, sleeping-IOP if ophthalmologists are going to optimize glaucoma therapies, said Yaniv Barkana, MD, Department of Ophthalmology, Assaf Harofeh Medical Center, Israel.

"What happens to IOP during the one-third of our lives that we're asleep? We know from several recent studies, and some not-so-recent, that supine, nighttime IOP is higher than daytime sitting IOP, in some cases on the order of 4 mm," Dr. Barkana said. "This may mean that glaucoma progression takes place while we are sleeping."

Unfortunately, Dr. Barkana said, there is not any single best way to measure IOP during sleep.

"Keep in mind that measuring nocturnal IOP is not the same as measuring sleeping IOP," he said. "We can measure IOP after waking patients, but even if we wake them gently, the change from sleeping to waking changes the equation."

Having an analysis of sleeping IOP could have implications for making a diagnosis of normal-tension glaucoma and increase the understanding of the mechanism of normal-tension glaucoma, according to Dr. Barkana. It may also alter treatment regimens.

"It may be that we choose to design and pursue therapies designed to blunt the sleeping IOP rise," he said.

Tools may become available for clinicians in the near future to help answer the question of what IOP is doing as we sleep, Dr. Barakana said. Implantable or contact lens-mounted monitors may allow for continuous IOP monitoring that may lead to new ways of thinking about glaucoma management.