Engineering the gift of sight

A multidisciplinary collaboration of LSU and Tulane researchers is using high-powered computing and mechanical engineering to learn more about glaucoma.

By J.T. Lane

The eye is an amazing labyrinth of nerves, blood vessels, receptors, connective tissues and muscles. These parts work together to allow us to detect an endless spectrum of colors, to see objects miles away, and to squint at the brightest of lights. They help us see the impressionism of Monet, the aurora borealis in Alaska, and the spectacular special effects of our favorite films.

However, along with the eye's great complexity comes a great chance that this delicate system could be damaged by disease or destructive conditions. One such condition is glaucoma-a disease that, according to the Glaucoma Research Foundation, affects more than 3 million Americans and is one of two leading causes of blindness in the United States. Only half of the 3 million people affected actually know they have the disease, which doctors and researchers are still working to understand.

Just as the various parts of the eye come together to give sight, a group of doctors and researchers from the Eye Center at the LSU Health Sciences Center in New Orleans, Tulane University, and the LSU Biological Computation and Visualization Center (BCVC) in Baton Rouge have joined together to gain insight into the causes of glaucoma and develop tools to fight it.

Glaucoma is a group of eye diseases that gradually steals sight without warning and often without symptoms. Blindness and vision loss are caused by injury to the optic nerve head, located at the back of the eye, which communicates all the images we see to the brain. The eye is a pressurized organ and doctors once thought that glaucoma was caused by high intraocular pressure (pressure inside the eye), but research has shown it is simply an indicator of glaucoma.

"The eye is like a basketball, except that it keeps its round shape and pressure with fluid instead of air," says J. Crawford Downs, assistant research professor of ophthalmology at the LSU Eye Center. "When intraocular pressure is high, that pressure can sometimes impact the optic nerve head, killing the nerves that transmit visual information to the brain."

The optic nerve head support structure is a meshwork of connective tissues that span a small opening at the back of the eye. It is the weak spot in an otherwise strong sclera, the outer wall of the eye. When pressure becomes too great, the optic nerve head bears the brunt of the effects of the pressure. Doctors have learned that the amount of pressure a person can tolerate varies. There are cases of glaucoma in patients with normal pressure, as well as cases where patients have high intraocular pressure, but no glaucoma.

Along with Downs, Claude Burgoyne, M.D., professor of ophthalmology and neuroscience and director of the glaucoma service of the LSU Eye Center; Richard Hart, professor and chairman of the Tulane Department of Biomedical Engineering; Francis Suh, professor of biomedical engineering at Tulane; and Sanjay Kodiyalam, senior postdoctoral researcher in the LSU BCVC; are working to find relationships between intraocular pressure and the development and progression of glaucoma. The team is taking a unique approach-it is one of only a few groups in the world to focus on the biomechanics of the optic nerve head.

Because of the complexity and small size of the optic nerve head, the team is using an engineering approach known as finite element analysis, which allows them to break up the complex structure into smaller parts that can be modeled and analyzed on a computer. Finite element modeling can be used to determine the effects of force and pressure on complex load-bearing structures, most commonly on buildings and bridges.

For the past two years, the LSUHSC and Tulane researchers have provided LSU's Kodiyalam with the connective tissue structure and three-dimensional visualization of the optic nerve head at micron-scale units, equal to one thousandth of a millimeter. Using that information, he is building full-scale biomechanical models of the optic nerve head.

"With a model of the optic nerve head, we can set a certain pressure and other conditions, simulate the impact on the structure of the eye, and predict where failure of the structure will likely occur," says Kodiyalam, a computational physicist.

Using the 256-processor Super Helix computer cluster in the BCVC, Kodiyalam can program the model to apply pressure on the virtual eye and determine the deformation of the optic nerve head structure-a deformation that could lead to glaucoma and blindness. In the future, he could also use the models to determine why glaucoma may not exist in the presence of high pressure and look for trends in different subgroups of people, such as African-Americans and people over the age of 60, who have the highest incidences of glaucoma nationwide.

After their analyses are complete and a more thorough understanding of glaucoma is accomplished, the researchers hope to develop a test to determine individual causes of glaucoma.

"Right now, when doctors diagnose glaucoma, the resulting treatment is partly based on a gut feeling. By developing an individualized test to assess specific target causes, doctors will be able to better treat the patient," says Downs.

The LSU BCVC is also aiding another research team focusing on elevated eye pressure. Sumanta Acharya, the LSU L.R. Daniel Jr. Professor of Mechanical Engineering, along with Roger Beuerman and Arto Palkama at the LSU Eye Center, are looking at particle depositions in the fluid outflow pathway of the eye.

Using a geometrical model of the eye and computational simulations, they are determining how the deposits contribute to increased intraocular pressure and the development of glaucoma. They have explored computer-generated virtual surgical procedures to provide surgeons a better understanding of how such procedures affect pressure and flow in the eye. Acharya and his group are also exploring drug delivery and transport patterns.

For both teams, future collaboration will be facilitated by the LSU Center for Computation and Technology. In addition, LSU will soon be linked to the LONI/LambdaRail high-bandwidth optical network, which will allow real-time exchange of extremely complex data and images between the campuses. The National LambdaRail project is an initiative of U.S. research universities and private sector technology companies to build a virtual supercomputer by linking the country's most powerful computers via a fiber-optic network. LONI, the Louisiana Optical Network Initiative, will link Louisiana's universities to the National LambdaRail.