Abstract
Before this study was done, there was a difference of opinion concerning whether intraocular pressure (IOP) was involved in producing optic nerve damage when there was glaucomatous damage to the optic nerve and characteristic visual field loss, even though the IOP was in the statistically normal range. This article reviews the findings of a collaborative study aimed at finding the answer to this question.
The level of pressure influences the course of normal tension glaucoma, as evidenced by a slower rate of incident visual field loss in cases with 30% or more lowering of intraocular pressure. The rate of progression without treatment is highly variable, but often slow enough that half of the patients have no progression in 5 years. A faster rate occurs in women, in patients with migraine headaches, and in the presence of disc hemorrhages. Some patients may experience greater benefit from lowering of IOP than others, but further research is needed to be able to identify those most likely to benefit.
As a group, patients with normal tension glaucoma benefit from lowering of IOP. Variable rate of deterioration, as well as lack of progression in a substantial number in 5 years, suggest that treatment should be individualized according to the stage of disease and rate of progression. Traits that help predict risk and rate of progression and response to treatment are beginning to become known and, when fully known, will help guide management decisions.