Glaucoma eye pressure higher in sleep: study

Some patients with glaucoma may have greater pressure in their eyes during sleep, meaning that the severity of the disease can go unrecognized during exams that only involve daytime office visits, a study said on Monday.

Higher intraocular pressure, the force within the eyeball, and greater daily fluctuation in pressure may increase the risk that glaucoma will develop or worsen, according to the report in the February issue of Archives of Ophthalmology.

Untreated glaucoma can lead to vision loss.

In an accompanying editorial, Dr. Robert Weinreb and Dr. John Liu of the University of California, San Diego, said understanding pressure changes could improve treatment of the disease.

“High intraocular pressure is recognized, perhaps, as the most important risk factor for the development of open-angle glaucoma and its progression,” they said in the editorial.

“However, many physiological and environmental conditions can affect intraocular pressure, and a single determination of intraocular pressure during regular clinic hours may not fully reveal its relationship to the optic nerve damage that accrues with glaucoma,” they said.

Previous studies have found the intraocular pressure may be higher when a person is lying down, according to the study. That is probably because the eye is level with the heart when lying down, increasing the resistance in flow of fluid in the eye and possibly creating additional pressure.

In the study Dr. Takeshi Hara of Jichi Medical School in Tochigi, Japan, and colleagues measured the intraocular pressure of 148 patients with untreated glaucoma at the Hara Eye Hospital in Utsunomiya, Japan.

They took measurements 12 times over the course of 24 hours, including every three hours during the night, according to the study.

Each time, they measured the pressure when the patient was sitting as well as when the patient was lying down, so that each patient had three levels: the sitting pressure, the lying pressure and the reproduced pressure, which was calculated by combining the sitting values when the patient was awake and lying values when the patient was asleep.

The researchers then calculated the peak, average and fluctuation of each of these levels, according to the study. The average peak pressure for seated patients was lower than those lying down, suggesting that measuring pressure only during the day does not paint an accurate picture of patients’ risks.

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