Effect of successful and partly successful filtering surgery on the velocity of glaucomatous visual field progression.

Objective: We sought to determine whether filtering surgery, even when only partially successful, delays or slows visual field (VF) progression.

Methods: The records of all patients seen in a glaucoma referral practice from 1999 to 2009 were reviewed. Group A comprised eyes with ≥ 5 VFs before surgery and group B comprised eyes with ≥ 5 VFs after surgery. Eyes in group B were further divided into those requiring postoperative topical ocular hypotensive therapy (group B-2) and those that did not (group B-1). Automated pointwise linear regression was used to determine global rates (dB/y) of change and progression endpoints. A progression endpoint was determined when 2 or more adjacent test locations in the same hemifield showed a threshold sensitivity decline at a rate of ≥ 1.0 dB/year with P < 0.01.

Results: A total of 206 treated eyes (206 patients; mean age, 63.8 ± 13.0 y; 11.3 ± 3.1 VFs; 6.4 ± 1.8 y follow-up) were included. Mean global VF progression rates in group A (-0.86 ± 0.8 dB/y) were faster than those in group B (-0.49 ± 0.9 dB/y, P < 0.01). Group A also had a greater risk of reaching a progression endpoint compared with group B (odds ratio = 2.41, P < 0.01). Groups B-1 and B-2 had different follow-up intraocular pressure means (12.7 ± 3.7 vs. 15.5 ± 2.7 mm Hg, respectively; P < 0.01) and peaks (19.4 ± 5.2 vs. 21.2 ± 4.2 mm Hg; P = 0.08). The velocity of VF progression was similar for groups B-1 and B-2 (-0.40 ± 0.6 vs. -0.58 ± 1.1 dB/y; P = 0.22) and there was no significant difference between the 2 groups regarding the risk of reaching a progression endpoint (odds ratio = 0.83, P = 0.62).

Conclusions: Filtering surgery reduces the rate of disease progression and this effect persists even if adjunctive glaucoma medical therapy is required.