Improvement of visual field indices after surgical reduction of intraocular pressure

In a prospective case series (consecutive patients) of 30 eyes from 30 subjects with medically uncontrolled glaucoma being treated at a hospital-based, referral glaucoma service, we sought to ascertain if a surgically obtained reduction of intraocular pressure (IOP) in human glaucomatous eyes is paralleled by an improvement of the visual field. Uncomplicated limbus-based trabeculectomy was performed in 13 men and 17 women familiar with computerized perimetry testing, with a pupil diameter of at least 4 mm (measured at the Goldmann perimeter bowl), a best-corrected visual acuity of 20/20 in both eyes, and a Mean Sensitivity (MS) index greater than 10 dB. The main outcomes measured were: visual field data (Octopus, program G1) and IOP (mean of the two highest values during the diurnal curve) obtained 3 days before and 3 months after surgery in both the operated and the fellow eyes. In the operated eyes, an increase of MS (from 17.2 +/- 2.4 to 18.9 +/- 2.8, P < .000001, paired samples two-tailed t test) was observed. Meanwhile, the Corrected Loss Variance (CLV) remained substantially the same (46.8 +/- 12.2 before, vs 47.3 +/- 13.4 after; P = .87, paired samples two-tailed t test). The increase in MS was positively correlated with the amount of IOP reduction (linear regression: r = 0.901, P < .00001). No statistically significant change of either MS or CLV values occurred in the fellow eyes. The correlation between the amount of IOP reduction and the increased MS suggests that, in the short term, reducing the IOP may improve visual function to some extent. The apparent lack of correlation between the amount of IOP reduction and the CLV may indicate that the depth of the preexistent glaucomatous scotomas remains unchanged.