Impact of intraocular pressure fluctuations on progression of normal tension glaucoma

AIM:To investigate short-and long-term intraocular pressure(IOP)fluctuations and fur ther ocular and demographic parameters as predictors for normal tension glaucoma(NTG)progression.METHODS:This retrospective,longitudinal cohort study included 137 eyes of 75 patients with NTG,defined by glaucomatous optic disc or visual field defect with normal IOP(<21 mm Hg),independently from therapy regimen.IOP fluctuation,mean,and maximum were inspected with a mean follow-up of 38 mo[standard deviation(SD)18 mo].Inclusion criteria were the performance of minimum two 48-hour profiles including perimetry,Heidelberg retina tomograph(HRT)imaging,and optic disc photographs.The impact of IOP parameters,myopia,sex,cup-to-disc-ratio,and visual field results on progression of NTG were analyzed using Cox regression models.A sub-group analysis with results from optical coherence tomography(OCT)was performed.RESULTS:IOP fluctuations,average,and maximum were not risk factors for progression in NTG patients,although maximum IOP at the initial IOP profile was higher in eyes with progression than in eyes without progression(P=0.054).The 46/137(33.5%)eyes progressed over the followup period.Overall progression(at least three progression confirmations)occurred in 28/137 eyes(20.4%).Most progressions were detected by perimetry(36/46).Longterm IOP mean over all pressure profiles was 12.8 mm Hg(SD 1.3 mm Hg);IOP fluctuation was 1.4 mm Hg(SD 0.8 mm Hg).The progression-free five-year rate was 58.2%(SD 6.5%).CONCLUSION:Short-and long-term IOP fluctuations do not result in progression of NTG.As functional changes are most likely to happen,NTG should be monitored with visual field testing more often than with other devices.