Purpose: To investigate the impact of surgical or medical reduction of intraocular pressure (IOP) on progressive normal-tension glaucoma followed up over 15 years.
Methods: Sixty eyes of 60 patients were divided into 3 intervention groups: group 1 (trabeculectomy, n = 17); group 2 (IOP reduction rate ≥15% with prostaglandin analogs, n = 24); and group 3 (IOP reduction rate <15% with prostaglandin analogs, n = 19). The preintervention and postintervention mean deviation (MD) slopes and IOP were compared. Factors associated with the rate of visual field progression were identified by multiple regression analysis.
Results: The mean follow-up was 19.8 years. In group 1, the preintervention and postintervention IOPs were 14.7 ± 1.3 and 9.1 ± 2.0 mmHg, respectively (P < .001, 38% reduction). The MD slope decreased significantly after trabeculectomy (-0.86 ± 0.51 versus -0.19 ± 0.20 dB/y; P < .001). In group 2, the preintervention and postintervention IOPs were 14.7 ± 1.5 and 11.7 ± 1.2 mmHg, respectively (P < 0.001, 20% reduction), with significant differences in the MD slope (-0.52 ± 0.37 versus -0.31 ± 0.30 dB/y; P = .019). In group 3, the preintervention and postintervention IOPs were 14.4 ± 1.8 and 13.2 ± 1.6 mmHg, respectively (P < 0.001, 8% reduction), with no differences in the MD slope (-0.40 ± 0.27 versus -0.50 ± 0.65 dB/y; P > .05). Multiple regression analysis showed that the average IOP, IOP reduction rate, and preintervention MD slope were related to the extent of the postintervention reduction in the MD slope. The difference in the preintervention and postintervention MD slopes significantly correlated with the rate of IOP reduction (r = 0.559, P < .001).
Conclusions: A pressure-dependent maintenance effect of the visual field was confirmed in progressive normal-tension glaucoma.
Keywords: Intraocular pressure reduction; Normal-tension glaucoma; Visual field progression.