Evaluation of ganglion cell-inner plexiform layer thickness in the diagnosis of preperimetric glaucoma and comparison to retinal nerve fiber layer.

Purpose: The aim of this study was to evaluate the diagnostic ability of optic nerve head (ONH), RNFL, and GC-IPL parameters in differentiating eyes with PPG from normals. Methods: This was a retrospective, cross-sectional, observational study. We studied 73 eyes of 41 patients and compared them to 65 eyes of 34 normal persons. Each patient underwent detailed ocular examination, standard automated perimetry, GC-IPL, ONH, and RNFL analysis. PPG was defined as eyes with normal visual field results and one or more localized RNFL defects that were associated with a glaucomatous disc appearance (e.g., notching or thinning of neuroretinal rim) and IOP more than 21 mm Hg. Diagnostic abilities of GC-IPL, ONH, and RNFL parameters were computed using area under receiver-operating curve (AUROC), sensitivity and specificity, and likelihood ratios (LRs). Results: All GC-IPL parameters differed significantly from normal. The ONH, RNFL, and GC-IPL parameters with best area under curves (AUCs) to differentiate PPG were vertical cup to disc ratio (0.76), inferior quadrant RNFL thickness (0.79), and inferotemporal quadrant GC-IPL thickness (0.73), respectively. Similarly, best LRs were found for clock hour 5, 6, and 12 thicknesses among RNFL; inferior sector and inferotemporal sector thicknesses among GC-IPL parameters. Conclusion: Diagnostic abilities of GC-IPL parameters were comparable to RNFL parameters in differentiating PPG patients from normals. The likelihood of ruling in a disease was greater with GC-IPL parameters.

Linear discriminant score for differentiating early primary open angle glaucoma from glaucoma suspects.

PURPOSE: To determine the diagnostic accuracy of a linear discriminant function (LDF) based on macular ganglion cell complex (GCC), optic nerve head (ONH) and retinal nerve fibre layer (RNFL) for differentiating early primary open-angle glaucoma (POAG) from glaucoma suspects. METHODS: In this cross-sectional study, data from consecutive 127 glaucoma suspects and 74 early POAG eyes were analysed. Each patient underwent detailed ocular examination, standard automated perimetry, GCC and ONH and RNFL analysis. After adjusting for age, gender and signal strength using the analysis of covariance; Benjamin-Hochberg multiple testing correction was performed to detect truly significant parameters to calculate the LDF. Subsequently, diagnostic accuracy of GCC and ONH and RNFL were determined. The obtained LDF score was evaluated for diagnostic accuracy in another test set of 32 suspect and 19 glaucomatous eyes. Data were analysed with the R-3.2.1 (R Core Team 2015), analysis of variance, t-test, Chi-square test and receiver operating curve. RESULTS: Among all GCC parameters, infero temporal had the best discriminating power and average RNFL thickness and vertical CDR among ONH and RNFL parameters. LDF scores for GCC had AUROC of 0.809 for a cut-off value 0.07, while scores for ONH and RNFL had AUROC of 0.903 for a cut-off value - 0.24. Analysis on combined parametric space resulted in avg RNFL thickness, vertical CDR, min GCC + IPL and superior GCC + IPL as key parameters. LDF scores obtained had AUROC of 0.924 for a cut-off value 0.1. The LDF was applied to a test set with an accuracy of 84.31%. CONCLUSION: The LDF had a better accuracy than individual GCC and ONH and RNFL parameters and can be used for diagnosis of glaucoma.