Purpose
To investigate the risk factors in normal tension glaucoma (NTG) with intraocular-pressure (IOP) < 15mmHg
Methods
Seventy eyes of NTG with 24-h diurnal intraocular-pressure (IOP) < 15 mmHg were retrospectively included in this study. We employed two definitions for visual field (VF) progression: (1) Collaborative Normal Tension Glaucoma Study (CNTGS) VF criterion. (2) an annual decrease in Mean deviation (MD) slope less than -0.33dB/year (MD slope criterion).To identify factors associated with VF progression, we adopted multivariate logistic regression analysis, employing VF progression as the outcome variable and several demographic and clinical parameters as explanatory variables. The latter included: age, refraction, baseline MD, baseline IOP before treatment, IOP parameters during follow-up period including average and standard deviation of IOPs, and disc hemorrhage (DH) development during follow-up.
Results
Mean age was 57.1 yrs. Mean follow-up periods was 11.3 yrs. Mean IOP during follow-up was 12.2 mmHg. DH was observed in 34 of 70 eyes. In the multivariate model, average IOP (RR 0.546, P=0.049) was detected as a risk factor for VF progression by CNTGS criterion. According to MD slope criterion, DH (RR 3.059, P=0.0362) was associated with VF progression. In comparison of the clinical characteristics between the progression and non-progression groups by CNTGS and MD slope criteria, development of DH was significantly more in VF progression group by both criteria, and average IOP was significantly higher in VF progression group by CNTGS criterion.
Conclusions
Higher average IOP and development of DH during the follow-up period were risk factors for progression in NTG with IOP ≤ 15mmHg