Glaucoma is an eye disease affecting about 5 percent of the population above 70 years of age. It is the second most common cause of blindness and though it may be possible to decelerate the disease, there is no cure. Investigating the eye pressure and understanding the biomechanics of the eye is a necessity to be able to detect glaucoma and set the correct diagnose. “The problem today is that there is no good way to determine the eye’s biomechanics” says Per Hallberg, whose work is to change that.
Hallberg started his career as an engineer and now has a doctorate in biomedical engineering. Currently he is running the project Models and measuring methods for determination of the eye’s biomechanics at Umeå University and the university hospital. He explains how glaucoma means that the optic nerves die. It can affect one or both eyes and is a slow process, usually discovered by the gradual reduction of the visual field.
“If only one eye is affected you tend to compensate it with the other, the disease can be rather difficult to discover” says Hallberg, “between 30 and 40 percent of the visual field is usually gone when the correct diagnose is set.”
Glaucoma has a controversial background. It is known to be age related, but young people can get it too and even be borne with glaucoma, although it is rare.
“In those cases it is genetic rather than age related, but much is still uncertain” says Hallberg.
He explains that eye pressure is normally measured to discover different courses of disease where glaucoma is one. What you measure is the liquid pressure of the aqueous humor in the eye and a high value means an increased risk of developing glaucoma. Eye drops that lower the pressure is a method used to decelerate already developed glaucoma. Lower the pressure is the only existing form of treatment.
“It becomes a lifelong process, but it slows down the progression so you can keep the disease under control” Hallberg says.
Today, a more than fifty year old method, called the Goldmann method, is standard for measuring eye pressure. The problem is that the method has a number of known sources of error. Hallberg explains that for starters, it is very dependent on the eye’s biomechanics without taking possible variations into account. The Goldmann method is based on the presumption that all eyes chare the same biomechanics, meaning the measurements will be correct as long as long as the patient falls into the “normal eye” category. But for people who differ from this norm, the measurements will be misleading. The pressure will appear to be lower than it actually is, meaning patients in the risk zone may be missed. Also, nowadays it is common to correct visual defects with laser technique, something that changes the conditions for the Goldmann method which again will lead to the wrong measured pressure value.
“Most people who have had this form of surgery have not reached the glaucoma age yet”, Hallberg points out, “but it will be a problem in the future if we don’t find a new method.”
Therefore, what Hallberg and his team, consisting of seven people from different departments, want to achieve with their project is the development of new measuring methods of the eye pressure and also categorize the biomechanics of the eye.
“It’s about deciding and describing the biomechanics in everything from stiffness and linear strain to capillary forces” Hallberg summarizes, “all to avoid the risk of incorrect measurements.”
The project is young, there are still many studies and tests that need to be done.
“We are still in the analysis phase and there is data we need to analyze in several steps. But the first tests still show that we actually can determine eye pressure more accurate than today’s standard” Per Hallberg concludes and looks forward to the future development of his project.
CMTF, c/o Tillämpad fysik och elektronik
Umeå universitet, 901 87 Umeå
Tel: +46 (0)90-786 96 38.
E-post: Britt Andersson.
