IOP not the only answer in glaucoma

MIAMI — Although recent clinical trials have linked intraocular pressure lowering with reduction of glaucoma progression, IOP should not be the sole factor on which treatment is determined, said David S. Greenfield, MD, in an analysis of recent glaucoma trials.

Dr. Greenfield spoke on how the definition of glaucoma has changed and how little is still known about the pathology of the disease here at the Bascom Palmer Eye Institute Inter-American meeting.

Although recent large-scale clinical trials have emphasized the importance of lowering IOP, they present different results in different patient populations, Dr. Greenfield said. In addition, they define their success and the pathology of the disease differently, he said.

The traditional definition of glaucoma, as a disease caused by elevated IOP, is no longer accepted, Dr. Greenfield said. Glaucoma is now considered a neurological disease of the optic nerve head in which elevated IOP is a risk factor, he said. The role of IOP still needs to be determined because there is a subgroup of patients who continue to progress despite having normal IOP levels.

Studies of normal tension glaucoma have shown that a history of disc hemorrhages and migraine are risk factors for the disease. In these trials, IOP was not found to be a significant risk factor, Dr. Greenfield said. Researchers believe disc hemorrhage may induce a vascular insult to the optic nerve. The rate of glaucoma progression has been seen to be directly related to the number of optic disc hemorrhages in some retrospective studies, he said.

Recently some glaucomatologists have begun to distinguish between two disease processes: pressure-dependent and non-pressure-dependent glaucoma, Dr. Greenfield said. Questions still to be resolved include how best to treat pressure-dependent and non-pressure-dependent glaucoma, he said.