Authors: AC Viswanathan, FW Fitzke, RA Hitchings.

Institute of Ophthalmology, Bath Street, London, UK and Moorfields Eye Hospital, City Road, London, UK.

Background: PROGRESSOR for Windows is a computerized system for the analysis of glaucomatous field progression incorporating a graphical user interface. The software package includes spatial filtering, which has been shown to reduce long-term fluctuation(1). However, some spatial processing, such as Gaussian filtering, may ‘blur’ early focal defects.

Purpose: To determine the role of Gaussian filtering in the early detection of glaucomatous loss.

Methods: 19 field series from untreated normal-tension glaucoma patients which an experienced observer judged as deteriorating were studied. The time taken from the start of each series until progression criteria (slope worse than -1 dB for inner points, -2 dB for edge points, p < 0.05) were satisfied by at least one retinal location was calculated with and without Gaussian filtering.

Results: The unfiltered fields detected progression earlier than the filtered fields in 3 of the 19 field series (mean 1.18 yrs, sd 0.30 yrs). The filtered fields detected progression earlier in 5 series(mean 1.04 yrs, sd 1.48 yrs). Both filtered and unfiltered fields detected progression at the same test in 11 field series. There was no predominance of focal defects in the series where progression was detected earlier by the unfiltered fields.

Conclusions: PROGRESSOR for Windows is a convenient software tool for analyzing glaucomatous field decay. Gaussian filtering reduces long-term fluctuation without delaying the detection of early loss in normal-tension glaucoma.

References

1. FW Fitzke, DP Crabb, AI McNaught, DF Edgar, RA Hitchings. Image processing of computerised visual field data. Br. J. Ophthalmol. 1995; 79: 207-212

(Presented at the XIIth Meeting of the International Perimetric Society, Wuerzburg 1996)