Cataract surgery slows the slow component of visual field decay but not the fast component in glaucoma patients

Abstract

Purpose: To evaluate the influence of cataract surgery on the fast and slow components of visual field decay rate in a group of glaucoma patients.

Methods: This is a retrospective noncomparative interventional study. Eighty-five eyes of 68 patients with open-angle glaucoma who had cataract extraction were included. All patients had five or more reliable SITA standard 24-2 visual fields both before and after surgery. Pointwise exponential regression was used to perform trend analysis on thresholds at visual field locations before and after cataract surgery. The visual field locations were ranked according to the rate of decay and partitioned into slow and fast groups. A univariate linear regression of mean deviation (MD) and pattern standard deviation (PSD) was performed.

Results: Mean values for MD and PSD were -5.51±5.06, 5.68±4.07 dB before and -5.04±4.92, 5.95±4.11 dB after cataract surgery (P=0.002, P=0.003). There was no significant change in the MD rate after surgery (P=0.476), whereas PSD rate increased significantly (P=0.017). The average visual field decay rate for all locations was 2.05±2.93 %/year before and 2.19±2.07%/year after surgery, and was not statistically significant (P=0.224). However, when visual field decay rates were partitioned into slow and fast components, the average slow component rate was 0.48±0.73 %/year before and slowed significantly to 0.26±0.42 %/year after surgery (P=0.037), whereas there was no significant change in the fast component rate (P=0.290). Visual field mean threshold showed an improvement immediately after surgery of 1.88±1.73 dB for all test locations, 0.51±2.13 dB for the slow component and 2.82±2.13 dB for the fast component (P<0.001, P=0.019, P<0.001).

Conclusions: Although there was no significant change in MD rate after surgery, the decay rate of the slow component was significantly slowed. In addition, there was no significant change in the fast visual field decay rate after surgery, while PSD rate increased significantly. These results indicate that cataract formation may be the main contributing factor for deterioration of the slow component rate of decay and affects relatively little the fast component rate of decay. We conclude that the fast component may be used to monitor glaucomatous visual field progression in glaucoma patients with cataract or in those having cataract extraction.

Keywords: 445 cataract • 642 perimetry • 758 visual fields