Protein biomarker could potentially catch glaucoma sooner

Glaucoma has been called the "sneak thief of sight," because real damage can occur to patients' vision before any telltale symptoms are evident. Researchers may have found a biomarker that can detect this theft.

A biomarker discovered by researchers at Washington University School of Medicine in St. Louis, Missouri, may mean that someday doctors of optometry might be able to detect glaucoma damage before there is significant structural or functional loss. The study, "GDF15 is elevated in mice following retinal ganglion (RGC) cell death and in glaucoma patients," appeared in the May 4 online issue of JCI Insight.

Glaucoma is the second leading cause of blindness in the world. The Centers for Disease Control and Prevention estimate that 2.2 million Americans, 40 years and older, have glaucoma. If untreated, progressive damage to the optic nerve can lead to blindness. That's why early detection and intervention is so critical to slowing its progression.   The study's goal was "to identify specific markers of RGC death that could potentially be used to accurately and reliably predict or measure glaucomatous neurodegeneration," researchers said. 

That molecular marker they were looking for was growth differentiation factor 15 (GDF15), a protein which increased in the aqueous humor of study patients with primary open-angle glaucoma. Not only did GDF15 increase, but the ganglion cell layer could be the source of the protein and its diffusion. 

Further studies are needed, the researchers said, to see if the protein can be applied in clinical settings. 

"In this study, we have, to our knowledge, characterized in mice and rats a novel molecular marker of glaucomatous neurodegeneration," the researchers say. 'We have further validated our findings in human glaucoma patients with varying degrees of disease severity. These results highlight a protein with potential use as a marker of glaucomatous neurodegeneration." 

Promising results

Murray Fingeret, O.D., founding member of the Optometric Glaucoma Society, who serves on the board of directors for The Glaucoma Foundation, called the study's findings exciting and very promising. 

"This is an important finding, but it is early," Dr. Fingeret says. "It's not clear how this information will be used clinically. What kind of test will be needed to measure this? The sample from the humans was taken at the time of eye surgery—obviously that is not feasible in everyday clinical practice. How early will this protein be found in people developing glaucoma? If validated and some form of a test is created, this could be an important method to confirm cases of glaucoma, especially in those individuals who are not good test takers (visual fields). 

"The results of the study don't change anything doctors of optometry do today, but it may change how we do things in the future, depending upon how this information is developed," he adds. "The idea that a protein is made as cells die is not novel, but the fact that the protein was isolated is. There's still a long way to go."