Abstract
Purpose: :
To determine the effect of trabeculectomy surgery on the Visual Field Index (VFI), Mean Deviation (MD), and Pattern Standard Deviation (PSD) for a group of patients with advanced glaucoma.
Methods: :
All visual fields from 1987-2001 were reviewed for a group of 36 eyes (36 patients) from the ATT arm of AGIS who underwent trabeculectomy. The MD, PSD, and VFI were extracted from each visual field. Data were censored at the point of any subsequent intraocular surgery. MD, PSD, and VFI were followed longitudinally for each patient. The slopes of these indices before and after trabeculectomy were compared. Locally weighted scatterplot smoothing (LOWESS) methods were used to compare the trajectories of the visual field parameters before and after trabeculectomy for the group of patients. Correlation coefficients between baseline MD, PSD, and VFI were determined.
Results: :
Patients were followed for an average of 3.7 yrs (SD 2.4 yrs) prior to trabeculectomy and 3.8 yrs (SD 2.7 yrs) after trabeculectomy. The baseline MD was -11.5dB (SD 5.8dB), PSD was 8.6dB (SD 3.3dB), and VFI was 69.4% (SD 19.7%). The mean change from baseline to immediately before trabeculectomy was -2.9dB (SD 4.7dB) for MD, 0.6dB (SD 2.5dB) for PSD, and -10.1% (SD 14.3%) for VFI. The mean change from immediately after trabeculectomy to the end of followup/censoring was -1.7dB (SD 3.3dB) for MD, -0.2dB (SD 2.0dB) for PSD, and -7.5% (SD 17.2%) for VFI. On LOWESS plots, MD and VFI both showed a similar downward trend prior to trabeculectomy with stabilization after trabeculectomy. There was very minimal change in the trajectory of the decline in PSD before and after trabeculectomy. Baseline VFI and baseline MD were highly correlated (r=0.95). There was less correlation between baseline VFI and PSD, and baseline VFI and PSD (r=-0.69 and r=-0.63, respectively).
Conclusions: :
Before trabeculectomy surgery, AGIS patients in the ATT arm exhibited a decline in MD, PSD, and VFI. Following trabeculectomy, the MD and VFI parameters stabilized while the PSD continued to decline over time. MD and VFI may be more useful than PSD in capturing the impact of trabeculectomy surgery on visual function. There appears to be little differentiation between the information captured in the MD and VFI parameters.
Keywords: perimetry • visual fields