INCIDENCE OF ELEVATION OF INTRAOCULAR-PRESSURE OVER TIME AND ASSOCIATED FACTORS IN NORMAL-TENSION GLAUCOMA

Purpose: The authors determine whether intraocular pressure (IOP) incr eases to levels that challenge the diagnosis of normal-tension glaucom a (NTG) and determine clinical factors associated with the IOP elevati on. Methods: Forty patients with NTG who met the following enrollment criteria were selected: IOPs less than 21 mm Hg during initial 24-hour pressure curve and throughout the subsequent 12 months; examined ever y 1 to 4 months for at least 4 years; and no ocular hypotensive treatm ent. The eye with the higher mean IOP during the initial 24-hour press ure curve was selected from each patient. The observation period range d from 4.0 years to 7.8 years (mean, 5.2 years). Significant IOP eleva tion was defined as a significant increase (p < 0.05) of IOP over time , determined by Spearman rank correlation coefficient method. The IOP elevation was correlated to clinical factors by means of a logistic mu ltiple regression analysis (LOGIST procedure using PC-SAS, SAS Institu te, Inc. Cary, NC, U.S.A.). Results: Eleven eyes were rated positive f or IOP elevation. The regression model demonstrated that maximum IOP d uring the initial 24-hour pressure curve and the development of disc h emorrhage (DH) were significantly correlated with IOP elevation(p = 0. 006 and p = 0.049, respectively). The odds ratios calculated were 1.98 per 1 mm Hg rise of maximum IOP during the initial 24-hour pressure c urve and 6.54 for positive DH. Conclusions: Intraocular pressure might increase in NTG eyes following the initial diagnosis. A higher maximu m IOP during initial 24-hour pressure curve and the development of DH during follow-up was significantly associated with subsequent IOP elev ation in NTG patients.