Structural and functional correlations in the pre-perimetric and the initial stages of glaucomatous optic neuropathy

Abstract

Purpose:to study morphological and functional relationships in the early and preclinical diagnosis of glaucomatous optical neuropathy based on optical coherence tomography (OCT) of the retina and the data of electrophysiological research. Material and methods. Two clinical groups: (I) 35 patients (60 eyes) aged 49–70 (ave. 58.0 ± 5.3 yrs) with suspected glaucoma and (II) 21 patients (30 eyes) aged 46-68 (ave. 61.0 ± 4.8 yrs) with initial primary open-angle glaucoma (POAG), and a comparison group consisting of 36 relativelyhealthy subjects (41 eyes) aged 54–70 (ave. 62.0 ± 4.5 yrs), were subjected to spectral OCT by OСT Spectralis (Heidelberg Engineering, Germany). The thickness of the peripapillary layer of retinal nerve fibers (pRNFL), the minimum rim width (MRW), and the thickness of theretinal layers in the macular region that make up the ganglion cell complex (GCC) were evaluated. Spearman correlation analysis was used to identify correlations between OCT and electroretinography (ERG) data. Results.In patients with suspected glaucoma, changes in the parameters of transient pattern-ERG correlated with RNFL thinning in the macular region, inner plexiform layer (IPL), and ganglion cell layer(GCL) in the parafoveal area. In patients with initial glaucoma, changes in the retinal GCL were detected for the upper, lower, and temporal quadrants, while the nasal and central quadrants remained intact in all three GCC layers (RNFL, GCL, and IPL). In patients with suspected glaucoma, no statistically significant changes in the thickness of the pRNFL as compared with the norm were detected. Yet the MRW differed significantly from the comparison group. The highest number of correlations was found between the parameters of the ERGs and the thickness of the pRNFL. In patients with the initial stage of POAG, there was a significant increase in the thickness of RNFL in the temporal quadrant of the paramacular region. In our opinion, this phenomenon may be associated with the development of reactive gliosis being thereaction of neuroglia in response to changes in vascular and/or dystrophic homeostasis. Conclusion.Specific combinations of changes in the structural parameters of the retina and optic nerve head and the temporal and amplitude indices of the PERG and phototopic negative response have been found, justifying their use as combined markers of early and preclinical diagnosis of POAG.

Keywords

• preclinical diagnosis
• suspected glaucoma
• initial primary open-angle glaucoma
• electrophysiological examinations
• optical coherence tomography of the retina