More to glaucoma surgery than meets the eye

Researchers at the Centre for Eye Research Australia (CERA) have found a new potential cause of scarring after glaucoma surgery, revealing that physics, not just biology, may be to blame.

Glaucoma is an eye condition associated with high fluid pressure inside the eye and affects more than 300,000 Australians. If standard treatments fail, glaucoma surgery is used to allow some fluid to leak out of the eye into a space under the eyelid, lowering the pressure inside the eye. Unfortunately, for many people these operations don’t last forever because scar formation prevents the fluid from leaving the eye.

It has long been thought that biological components in the fluid may have inflammatory effects, which contribute to the scarring. However, CERA researchers have shown for the first time that there is more to the story, and the mechanical action and hydraulics of fluid passing through tissue may also contribute to scar formation.

The researchers, led by Associate Professor Michael Coote and Professor Jonathan Crowston, conducted glaucoma surgery in animals using a specially designed implant, which acts like a stent to keep the hole open longer.

In this experiment, the implant was inserted into the eye but not quite far enough to let fluid leak out of the eye. Once the eye had fully healed, the researchers injected sterile saline solution through the implant. Saline (salt water) was chosen because it is similar to the fluid inside the eye but doesn’t have any inflammatory biological components. They found that only three days after the saline was injected, the implants were working much less effectively.

“This is the first direct evidence that the mechanical movement of fluid out of the eye may actually be contributing to the scarring process,” said Craig Ross, a medical student who is currently working with the Glaucoma Research Unit at CERA.

The researchers hope that this new evidence will one day help improve glaucoma surgery techniques. “We need to remove enough fluid so that the pressure drops to a safe level, but our research suggests that if we remove too much, too fast, we may encourage scarring which will mean any improvement is short-lived,” said Craig.

Craig presented these findings and received a prize for Best Presentation by a Trainee at the Australian and New Zealand Glaucoma Interest Group (ANZGIG) meeting in Hobart last month.

Previously the work was presented at the International Glaucoma Surgery Meeting in Glasgow where the presentation was awarded the best scientific paper of the meeting.

The Royal Victorian Eye and Ear Hospital is collaborating closely with CERA on this project, as the sponsoring institution. CERA Managing Director Professor Jonathan Crowston stressed the importance of government funding to allow CERA to work closely with the Hospital and embed this research into the health system.

“This support facilitates development of such a device and increases the chances of it impacting large numbers of glaucoma patients,” said Professor Crowston.

Other project partners include the University of Melbourne and Grey Innovation, who recently received funding from the Victorian government to conduct a feasibility report on developing the new implant.

Source: Centre for Eye Research Australia