Purpose: The GDx (Laser Diagnostic Technologies, San Diego, CA) is a scanning laser polarimeter that assesses nerve fiber layer (NFL) thickness in vivo. The GDx provides 14 standard parameters. Recently, four new parameters (The Choplin number, The superior Mills Number, The Inferior Mills Number, The Linear Discriminant Function (LDF)) have been added. This last parameter is calculated from three already existing parameters. We are presenting sensitivity and specificity values for these four new GDx parameters.
Methods: We determined the sensitivity and specificity of these parameters in 241 glaucoma patients and 263 healthy volunteers, respectively.
Results: Sensitivity and Specificity of the four new parameters are presented, along with the area under the ROC (Receiver Operator Characteristic) curve. For comparison, the score of The Number, and of the maximum modulation (the best single parameter) are given.
Parameter: Sensitivity Specificity Area under the ROC curve
Choplin Number 62.7 87.6 0.865
Sup Mills Number 61.8 89.6 0.859
Inf Mills Number 50.6 92.2 0.871
LDF 60.6 85.3 0.819
The Number 77.2 89.1 0.902
Max Modulation 61.8 90.7 0.846
Conclusions: All four new parameters showed good discrimination between normals and glaucoma patients. They were all nearly as good as, or better than the maximum modulation parameter, which appeared to be the best single parameter up to now. None of the new parameters discriminated better than The Number. After incorporating the new parameters into the algorithm for The Number, it may even better discriminate between normals and glaucoma patients.
Proprietary Interest: F