The effects of glaucoma filtering surgery on the variability of diurnal intraocular pressure.

The results of this study indicate that filtration surgery reduces the mean diurnal IOP, the range of diurnal variation, and the day-to-day variability. The effect on the range is proportionally greater than on the other two parameters. Further study will be required to determine whether this selective effect makes surgical reduction of IOP any more effective in the prevention of further glaucomatous visual field damage than other therapeutic methods that lower mean IOP to the same degree.