Some patients with glaucoma appear to have higher pressure in their eyes during sleep at night than during the day when it is usually measured, possibly putting them at higher risk for progression of the disease than previously thought, according to a study in the February issue of Archives of Ophthalmology.
Higher intraocular pressure, the force within the eyeball, and greater daily fluctuation in pressure may increase the risk that glaucoma will develop or worsen. Intraocular pressure is usually measured during regular physician's visits, when patients are seated, according to background information in the article. However, previous studies have found that the intraocular pressure may be higher when a person is lying down, the authors report. This is probably because the eye is level with the heart when lying down, which increases the resistance in flow of fluid in the eye and may create additional pressure, they write.
Takeshi Hara, M.D., Jichi Medical School, 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. 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.