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SUMMARY Three successive fields of 136 eyes (86 patients) were extracted from our data base containing over 3000 visual fields performed on the Humphrey visual field analyser with program 30-2. Series of fields in which the second field was depressed relative to the first were selected for analysis to determine how much change between the first two fields was required to predict a downward trend as confirmed by the third field in the series. The data were stratified with respect to initial field damage. Seven regions of the visual field were analysed including the upper and lower temporal and nasal quadrants, the superior and inferior Bjerrum regions, and the whole field. Minimally damaged regions required between 4-7 and 5 6 dB change in mean sensitivity, whereas more damaged regions required between 5-5 and 7*2 dB change in mean sensitivity to have 95% confidence that the negative trend would be confirmed by the third field. The superior Bjerrum region was the most sensitive for the detection of change, and the lower temporal region was the least sensitive. We conclude from this series of data that large changes between two successive fields are required to be sure that the changes are due to disease rather than chance fluctuation. Where any doubt exists, the field should be repeated to confirm the reality of change.

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This paper presents the results of a study into the post-shutdown recovery behaviour of coal seam gas (CSG) wells and its application to estimating long-term field turndown capacity incorporating the impact of well performance recovery postshutdown. Queensland, Australia is currently host to a number of CSG to liquefied natural gas (LNG) projects under development. These projects aim to develop Queensland's vast CSG resources to supply domestic and international gas markets. However, the need to build field deliverability prior to the availability of export gas markets presents a significant challenge. CSG wells must be dewatered while gas production may be constrained. The ability to manage and forecast production performance in field turndown scenario is therefore critical. A study of production data from CSG production interruption events was conducted to determine how wells reacted to turndown of gas production rates. The study considered various production management strategies including partial choking and complete shut in of selected producers. Implications of the work include identification of criteria for selecting wells that are suitable for long-term turndown, the formulation of operational guidelines for minimising adverse post-shutdown production impacts, and estimation of long-term field turndown capacity through the application of the study results to a field production model.