According to the National Eye Institute common, an eye movement may be a cause of glaucoma in people with normal intraocular pressure . The study findings were published in Investigative Ophthalmology and Visual Science
The findings suggest that over time eye movement strains the optic nerve. The research may also explain why tension-lowering eye drops can improve normal-tension glaucoma. Elevated intraocular pressure within the eye is a widely recognized risk factor for glaucoma.
In a series of studies, Demer and colleagues explored whether repetitive strain from eye movements could damage the optic nerve and lead to vision loss . The researchers used magnetic resonance imaging ( MRI ) to directly visualize the optic nerve as people gazed in several directions, including straight ahead and in degrees of adduction and abduction.
They compared MRI findings from people with normal-tension glaucoma to those from healthy volunteers. Everyday eye movements are likely to put even more strain on the optic nerve, said Demer, as the ocular range of motion in the study is about half that achieved by people under normal conditions.
What is more, our eyes are in constant motion. Rapid eye movements called saccades occur approximately three times per second, or an estimated 183,000 times daily, including those during rapid eye movement sleep . "It is certainly plausible that some of these rapid eye movements would involve degrees of adduction that could have a physiological effect," he said.
In a separate study, Demer's team sought to understand what effect such forces might have on various eye structures. They found that adduction exerts stress on two key regions of the eye in the glaucoma: the junction between the optic nerve sheath and the outer layer of the eyeball, or sclera, and the junction where scleral tissue around the optic nerve.
The researchers also observed that the tissue of the sclera is not uniformly stiff. And the stiffer tissues of the eye shift mechanical stress to the more pliant tissues , a pattern that is consistent with the location of changes seen with glaucoma. Demarrated that is as if the peripapillary sclera is a like to stiff raft floating on the more mushy sclera.
The optic nerve sheath attaches to this raft of peripapillary sclera and with each adduction eye movement it causes whole optic nerve head to tilt. In addition, the biomechanical simulation showed that repetitive strain from eye motion exerts far greater stress on the optic nerve compared with elevated intraocular pressure.
If these findings are confirmed by additional studies, the next step is to investigate therapies that could possibly have relieved the strain produced by eye movement , "The meticulous investigations of the human orbit biomechanics done by Dr. Demer over the years have shed crucial insight into oculomotor function and disease, "said Houmam Araj.