Factors that predict the benefit of lowering intraocular pressure in normal tension glaucoma

Purpose: To study whether the benefit of lowering of intraocular pressure (IOP) varies according to certain traits. Design: Randomized clinical trial, secondary analysis. Methods: Visual field data were analyzed from 144 subjects (144 eyes) randomized not to receive IOP-lowering treatment or to have the IOP lowered by 30%. Survival analyses were applied to compare times to progression between groups. Changes in mean deviation global index over time were compared with multilevel random effects models. Results: By univariate analysis, the most readily demonstrated treatment benefit occurred in patients without baseline disk hemorrhage, of female gender, with family history of glaucoma, without family history of stroke, without personal history of cardiovascular disease, and with mild disk excavation; IOP lowering benefited females with migraine (P<.05) but perhaps without eliminating all migraine,associated risk. Conclusions: It is suggested that different factors may contribute to the glaucomatous optic neuropathy in different cases of normal tension glaucoma, interacting with IOP to different degrees and, thereby, affecting the magnitude of benefit of IOP lowering. Further study is required to establish interactions that would have implications for understanding the disease mechanisms in glaucomatous cupping, for guiding development of new treatment modalities, and for making clinical decisions regarding prognosis and management of individual patients.