Specification of progression in glaucomatous visual field loss, applying locally condensed stimulus arrangements

Abstract

Purpose: The goal of this work was to (i) determine patterns of progression in glaucomatous visual field loss, (ii) compare the detection rate of progression between locally condensed stimulus arrangements and conventional 6 degrees x 6 degrees grid, and (iii) assess the individual frequency distribution of test locations exhibiting a local event (i.e., an abrupt local deterioration of differential luminance sensitivity (DLS) by more than -10 dB between any two examinations).

Methods: The visual function of 41 glaucomatous eyes of 41 patients (16 females, 25 males, 37 to 75 years old) was examined with automated static perimetry (Tuebingen Computer Campimeter or Octopus 101-Perimeter). Stimuli were added to locally enhance the spatial resolution in suspicious regions of the visual field. The minimum follow-up was four subsequent sessions with a minimum of 2-month (median 6-month) intervals between each session. Progression was identified using a modified pointwise linear regression (PLR) method and a modified Katz criterion. The presence of events was assessed in all progressive visual fields.

Results: Eleven eyes (27%) showed progression over the study period (median 2.5 years, range 1.3-8.6 years). Six (55%) of these had combined progression in depth and size and five eyes (45%) progressed in depth only. Progression in size conformed always to the nerve fiber course. Seven out of 11 (64%) of the progressive scotomata detected by spatially condensed grids would have been missed by the conventional 6 degrees x 6 degrees grid. At least one event occurred in 64% of all progressive eyes. Five of 11 (46%) progressive eyes showed a cluster of events.

Conclusions: The most common pattern of progression in glaucomatous visual fields is combined progression in depth and size of an existing scotoma. Applying individually condensed test grids remarkably enhances the detection rate of glaucomatous visual field deterioration (at the expense of an increased examination time) compared to conventional stimulus arrangements.

Fig. 1

The 6 × 6° grid (a) was condensed in the region of interest (b) to achieve an individual locally condensed grid (c)

Fig. 2

Example of progression in depth and size (16 visits within 9 years). The test locations with confirmed progression are marked with red triangles. The initially normal and later pathologic test locations are marked with red frames. The four examples show the four different test point courses: (a) stable (b) variable (c) progression (d) stable. The events are marked with red clasps in the test points and with red and green bars in the inset (b). The nearly horizontal blue lines show the age-related normative DLS values at the selected stimulus locations. The red lines show the 95% CI. Blue circles highlight four progressive stimuli. Three of these non-edge locations are adjacent, i.e., they form a cluster with the distances less than or equal to the distances of the 6° × 6° rectangular Humphrey grid. Therefore, this set of visual fields record is classified as progressive

Fig. 3

a Box-and-whiskers plot and histogram of 10,537 differences between individual local DLS thresholds at third and fourth examination. Small grey circles indicate values outside the inner fence. Vertical ticks on the whiskers mark the 0.5%-, 2.5%-, 10%-, 90%-, 97.5%-, and 99.5% quantiles. The smooth red line is the density of the mixture of 23.6% of a central Laplace-distribution with parameter 4.35 and 76.4% of a central Laplace-distribution with parameter 1.35. b Densities of the mixture (red encompassing) and its components (symmetric triangles) with a shaded area that represents 5% of the area under the solid symmetric triangle, when the density axis is not logarithmic. DLS differences in that area are considered events

Fig. 4

Time for the first detection of progression for each grid. Locally condensed grids detect progression earlier than the 6° × 6° grid. Minimum follow--up time was 16 months, mean follow-up time was 30 months (2.5 years)

Fig. 5

A representative course of progression of glaucomatous visual field defects, examined with additional test points in the visual field area adjacent to the existing scotomata (scotoma-oriented perimetry (SCOPE). SCOPE finds progression 3.5 years before the conventional 6° × 6° grid