TY - JOUR
T1 - Variability and errors of manually digitized Goldmann visual fields
AU - Barry, Michael P.
AU - Bittner, Ava K.
AU - Yang, Liancheng
AU - Marcus, Rebecca
AU - Iftikhar, Mian Haris
AU - Dagnelie, Gislin
N1 - Funding Information:
This research was supported by grants from NIH K23 EY018356, to AKB; QLT Inc. (Vancouver, BC, Canada), to GD; and NIH T32 EY07143, to the Johns Hopkins Visual Neuroscience Training Program for MPB.
Publisher Copyright:
Copyright © 2016 American Academy of Optometry.
PY - 2016/6/21
Y1 - 2016/6/21
N2 - Purpose. Goldmann visual fields (GVFs) are useful for tracking changes in areas of functional retina, including the periphery, in inherited retinal degeneration patients. Quantitative GVF analysis requires digitization of the chart coordinates for the main axes and isopter points marked by the GVF operator during testing. This study investigated inter- and intradigitizer variability among users of a manual GVF digitization program. Methods. Ten digitizers were trained for 1 hour, then digitized 23 different GVFs from inherited retinal degeneration patients in each of three testing blocks. Digitizers labeled each isopter as seeing or non-seeing, and its target size. Isopters with the same test target within each GVF were grouped to create isopter groups. Results. The standard deviation of isopter group area showed an approximate square-root relationship with total isopter group area. Accordingly, the coefficient of variation for isopter group area decreased from 68% to 0.2% with increasing isopter group area. A bootstrap version of ANOVA did not reveal a significant effect of digitizers on isopter group area. Simulations involving random sampling of digitizers showed that five to seven digitizers would be required to catch 95% to 99% of labeling errors and isopter misses, on the basis of data discrepancies, with 99% probability. Conclusions. These data suggest that any minimally trained digitizer would be capable of reliably determining any isopter area, regardless of size. Studies using this software could either use five to seven minimally trained digitizers for each GVF, three digitizers who demonstrate low frequencies of errors on a practice set of GVFs, or two digitizers with an expert reader to adjudicate discrepancies and catch errors.
AB - Purpose. Goldmann visual fields (GVFs) are useful for tracking changes in areas of functional retina, including the periphery, in inherited retinal degeneration patients. Quantitative GVF analysis requires digitization of the chart coordinates for the main axes and isopter points marked by the GVF operator during testing. This study investigated inter- and intradigitizer variability among users of a manual GVF digitization program. Methods. Ten digitizers were trained for 1 hour, then digitized 23 different GVFs from inherited retinal degeneration patients in each of three testing blocks. Digitizers labeled each isopter as seeing or non-seeing, and its target size. Isopters with the same test target within each GVF were grouped to create isopter groups. Results. The standard deviation of isopter group area showed an approximate square-root relationship with total isopter group area. Accordingly, the coefficient of variation for isopter group area decreased from 68% to 0.2% with increasing isopter group area. A bootstrap version of ANOVA did not reveal a significant effect of digitizers on isopter group area. Simulations involving random sampling of digitizers showed that five to seven digitizers would be required to catch 95% to 99% of labeling errors and isopter misses, on the basis of data discrepancies, with 99% probability. Conclusions. These data suggest that any minimally trained digitizer would be capable of reliably determining any isopter area, regardless of size. Studies using this software could either use five to seven minimally trained digitizers for each GVF, three digitizers who demonstrate low frequencies of errors on a practice set of GVFs, or two digitizers with an expert reader to adjudicate discrepancies and catch errors.
KW - Digitize
KW - Error
KW - FieldDigitize
KW - Goldmann visual field
KW - Variability
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U2 - 10.1097/OPX.0000000000000869
DO - 10.1097/OPX.0000000000000869
M3 - Article
C2 - 27058594
AN - SCOPUS:84979483622
SN - 1040-5488
VL - 93
SP - 720
EP - 730
JO - Optometry and Vision Science
JF - Optometry and Vision Science
IS - 7
ER -