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lilian mohamed, Esteban Morales, Nucharee Parivisutt, Pradtana Hirunpatravong, Reza Alizadeh, Fei Yu, Abdelmonem Afifi, Kouros Nouri-Mahdavi, Joseph Caprioli; A Novel Index to Define the Rate of Visual Field Change in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4741.
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© ARVO (1962-2015); The Authors (2016-present)
To present a novel method (Progression Index) to measure the rate of glaucomatous VF progression on a normalized scale, and throughout the entire perimetric range.
In this retrospective, longitudinal, observational study, 8,486 eyes of 4,610 glaucomatous patients with a minimum of 6 visual fields (VF) and 3 years of follow up were included. To reduce noise, all threshold values in a series for a test location with Cook’s distance >1 or Studentized residuals >3 were removed. VF locations were partitioned into “decay exponential” or “improvement exponential” models, depending on the a prior linear trend. The Standardized Percentage Rate of Change (SPRoC) for each location was calculated. Criteria for statistically and clinically significant change at each location required the slope to be 1) beyond the 95% confidence interval, and 2) > three times the normal aging rate. A normalized Progression Index (PI) was calculated for each eye based on the sum of the SPRoC for decaying and improving locations with boundaries for maximum and minimum rates set by simulated VF series. The PI was normalized from -1 to 1 where -1 is fastest decay, 0 is no change, and 1 is fastest improvement. Eyes with PI scores of < −0.03 were categorized as progressors and those with PI < −0.14 were considered fast progressors; these values were based on an ROC curve from a separate VF database of expert evaluations of serial VFs.
The total number of VF exams was 89,704 with 425,039 test locations. A total of 2.8% of locations were removed. The proportion of decay, no change, and improvement for individual locations were 5.6%, 93.7%, and 0.7%, respectively. The mean SPRoC for the decay, no change, and improvement test locations were −5.0 (±5.6) %/year, and −0.6 (±2.5) %/year, and 4.5 (±3.7) %/year, respectively. These rates refer to the % of the entire perimetric range lost per year. A total of 1,801 (21.2%) eyes were categorized as progressors and 453 (5.3%) were categorized as fast progressors.
This method provides a normalized index for approximating the rates of worsening (or improvement) of serial perimetric measurements in glaucomatous eyes. The PI is designed to represent statistically and clinically significant change, operates over the entire perimetric range, and can be used to identify those patients who are fast progressors.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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