Comparison of ganglion cell-inner plexiform layer thickness in exfoliative glaucoma and primary open-angle glaucoma

Abstract

Purpose: To determine and compare the thickness of the ganglion cell-inner plexiform layer (GCIPL), the thickness of the retina nerve fiber layer (RNFL), and the parameters of the optic nerve head (ONH) in exfoliative glaucoma (XFG), primary open-angle glaucoma (POAG), and control eyes using optical coherence tomography (OCT).

Methods: The study was a retrospective observational cross-sectional study of 43 eyes of patients with XFG, 44 eyes of patients with POAG, and 37 eyes of healthy participants. Visual acuity, intraocular pressure, central corneal thickness, rim-area, disc-area, average cup/disc ratio, vertical cup/disc ratio, cup volume, average RNFL thickness, and GCIPL (average, minimum, superior, superotemporal, superonasal, inferior, inferotemporal, and inferonasal) thicknesses were determined.

Results: RNFL thicknesses were similar in the XFG and POAG groups (p = 0.065), and both glaucoma groups had significantly thinner RNFLs than the controls (p = 0.002). The XFG group had significantly thinner average and minimum GCIPLs compared to the POAG and control groups (p = 0.027, p < 0.001 for average thickness and p = 0.038, p < 0.001 for minimum thickness, respectively). No significant difference was found in the ONH parameters among the three groups except for rim-area and cup volume (p > 0.05 for all ONH parameters, p < 0.001 for rim-area, and p = 0.003 for cup volume). Mean visual field mean deviation was -11.6 ± 8.2 dB in the XFG group and -10.4 ± 9.3 dB in the POAG group (p = 0.453).

Conclusion: Eyes with XFG were found to have a thinner GCIPL (minimum and average) than eyes with POAG or from healthy controls, although the RNFL measurements were similar to those of eyes with POAG. GCIPL thickness may be a more valuable indicator than RNFL thickness in patients with XFG for early detection of glaucoma and/or for glaucoma progression measurement. There is still some debate in the literature about whether decreases in GCIPL thickness and RNFL thickness (and/or ONH parameter change) are the best indicators for early detection and progress measurement of glaucoma.

Keywords: Exfoliative glaucoma; Ganglion cell-inner plexiform layer thickness; Optical coherence tomography; Primary open-angle glaucoma; Retina nerve fiber layer thickness.