Evolving definition of glaucoma means treatment patterns will evolve, too

Glaucoma has long been defined as a disease characterized by elevated IOP. That definition, however, is changing to definethe disease as an optic neuropathy characterized by a specific pattern of optic nerve head and visual field damage. That'sthe word from Theodore Krupin, MD, Department of Ophthalmology, Sorrel Rosin Eye Center, Northwestern University,Chicago.

This change in definition reflects a new way of thinking about the disease, and thus, affects the preferred practice patternsfor ophthalmologists.

"Glaucoma is a progressive neurodegenerative disorder," Dr. Krupin said. "Elevated IOP is only a risk factor, not the diseaseper se."

Dr. Krupin noted that structural damage precedes functional change, and retinal nerve fiber layer injury can be observed upto 6 years before visual field defects are detected. Between 25% and 40% of optical nerve fibers can be lost from an eye thatretains a normal visual field.

Progression of glaucomatous neuropathy cannot always be prevented or slowed by reducing IOP, and glaucomatous opticneuropathy is not always associated with elevated IOP, Dr. Krupin said. Still, control of IOP is currently the only factorfor the disease amenable to modification by the clinician.

"What we have to remember is that the aim of our treatment is not simply to reduce IOP, it's halting the neurodegeneration ofthe retinal ganglion cells and their axons," Dr. Krupin said. "The ultimate aim is to halt progression before the stage ofsevere damage."

What does the future hold? Dr. Krupin says that the ultimate staging method would be an in vitro determination or detectionof an accelerated rate of retinal ganglion field death.

"This is the future of glaucoma staging and detection, and therefore, management. But it's still the future," Dr. Krupinsaid.