A Method to Measure the Rate of Glaucomatous Visual Field Change.

For VF locations with a negative trend, the decay PER model was applied, expressed as y = e ( a + bx ) , where y = sensitivity in decibels, a = constant, b = regression coefficient (slope), and x = time in years.

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For VF points with a positive trend, we used a mirror image approach, where the exponential function had an asymptote as a ceiling (the normal age-matched value for that particular test location plus twice its standard deviation).

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