Pointwise linear progression criteria and the detection of visual field change in a glaucoma trial

Abstract

Background Current pointwise linear regression (PLR) change criteria for visual field analysis are largely empirical. Methods Two independent sets of Humphrey Field Analyzer fields were analysed using PLR. Set i, 56 patients, and set ii, 97 patients, were followed over 16 months. Criteria were tested against set i, and then validated using set ii. Each criterion specified a fixed critical slope of 1 dB/year and with a range of significance from Po0.001 to 0.05. The criteria were varied by altering location number, cluster arrangement, and by requiring points to show change over both 12 and 16 months. True glaucomatous change was differentiated from noise by looking for exclusive progression (EP), the detection of progression without detection of improvement. Results Set i required 1 point to have a slope of 1 dB/year and Po0.05 labelled 64% progressing and 58% improving, whereas several stricter criteria were capable of detecting EP. Two points in a perimetric nerve fibre bundle (PNFB) cluster gave optimal EP detection, labelling 8.9% progressing in set i and 7.2% progressing in set ii with a cutoff P-value of 0.026 inset i and 0.013 inset ii. Conclusion Lax PLR criteria detect large amounts of change. Validating criteria using two data sets allow selection of better criteria, capable of detecting EP. The criterion involving 2 points changing in a PNFB cluster offers the best option for exclusively detecting progression.

Visual Field Progression in Glaucoma: Estimating the Overall Significance of Deterioration with Permutation Analyses of Pointwise Linear Regression (PoPLR)

“…Criteria for overall change (i.e., for the entire visual field) have been based, arbitrarily, on fixed numbers of changing test locations, [8][9][10][11][12] and change at individual test locations has been defined with similarly arbitrary criteria of slope and associated P value. [8][9][10][11]13,14 In consequence, criteria for visual field change with PLR are not adapted to an individual patient's data. Rather, their specificity is likely to vary between patients, making results difficult to interpret.…”

Specificity of the Program Threshold Noiseless Trend for Perimetric Progression Analysis

“…23,24 This criterion is less important in the TOP strategy than in others that analyze points of the visual field as totally independent from each other, since TOP uses information obtained from adjacent points in threshold measurement. This feature, together with spatial mathematical filtering criteria, means that clusters were not considered since they appear spontaneously.…”

Comparison of Standard Automated Perimetry, Short-Wavelength Automated Perimetry, and Frequency-Doubling Technology Perimetry to Monitor Glaucoma Progression

“…61 For PLR analyses, we used sensitivity loss ≥5% of mean normal per year for nonedge locations, and ≥10% of mean normal per year for edge locations at a significance level of P  < 0.05 as the pointwise criteria for visual field progression. These levels were chosen to approximate the commonly accepted criteria of more than 1 dB loss per year at a significant level on nonedge locations for SAP 32,43–45,47–51 and more than 2 dB loss per year on edge locations. 32,43,44,47 Although these criteria may be arbitrary, these rates of progression would be enough to raise concern about the need for more aggressive treatment for an average eye.…”

“…42–44 Although there is no “gold standard” for progression using PLR, 45,46 the commonly applied criterion of slope with SAP is more than 1 dB sensitivity loss per year at a significant level; 32,43–45,47–51 and as the edge locations are subject to more variability, 52 a steeper slope of 2 dB loss per year has been adopted for them. 32,43,44,47 Because we did not use the decibel scale in this study, we approximated what 1 and 2 dB loss per year would translate to in percent of mean normal.…”