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.