Structural and Functional Correlations in Patients with Advanced Stages of Primary Open-Angle Glaucoma

Purpose: To study the correlations in the diagnosis of patients with advanced stages of primary open-angle glaucoma (POAG) using data from electroretinography and optical coherence tomography (OCT) of the retina.

Methods. The study was performed in two clinical subgroups of patients (35 people, 55 eyes) with stages II and III POAG and the age-matched control group (28 healthy people, 32 eyes). The thickness of the ganglion cell complex (GCC), including the retinal nerve fiber layer (RNFL), the retinal ganglion cell layer (RGC), and the inner plexiform layer (INL) in the macular region, was assessed in nine segments. Correlation analysis of morphometric parameters of GCC in advanced POAG was performed with data from previously performed electroretinography: the transient pattern-ERG (T-PERG), stationary pattern-ERG (S-PERG), and photopic negative response (PhNR).

Results. Statistically significant (p < 0.01) thinning of all layers of the GCC was revealed in all studied sectors. Significant (p < 0.05) differences in all morphometric characteristics were recorded between the two subgroups. In patients of the 1st subgroup, the greatest differences in morphological parameters from the control group’s values were noted in the lower, upper parafoveal sectors of the RGC layer, as well as in the temporal perifoveolar quadrant. In the 2nd subgroup, significant changes in the thickness of the inner retina layers were recorded for the upper and lower peripheral sectors of the RNFL and the temporal para- and peripheral quadrants of the RGC layer. In the study of morphological-functional relationships, the most significant correlations were revealed for the parameters of S-PERG. The amplitude of S-PERG directly correlated with the thickness of RNFL in the nasal sector of the perifovea (r = 0.86; p < 0.01) in the 1st subgroup of patients and the thickness of the RGC in the nasal sector of the perifovea in the 2nd subgroup (r = 0.84; p < 0.01). Moderate relationships were revealed between the N95/P50 T-PERG index and the RNFL thickness in the upper sector of the perifovea (r = 0.46; p < 0.05), the peak N95 T-PERG latency, and the RNFL thickness in the upper sector of the perifovea (r = –0.43; p < 0.05) in patients of the 1st subgroup. In patients of the 2nd subgroup, there was a correlation between the amplitude of N95 T-PERG and the thickness of the RGC in the lower sector of the perifovea (r = –0.42; p < 0.01), the peak latency of N95, and the thickness of the RNFL in the upper sector of the parafovea (r = –0.31; p < 0.05). A direct correlation was established between the PhNR amplitude from the baseline and the thickness of the RGC layer in the perifovea’s temporal sector (r = 0.72; p < 0.01) in patients with stage II POAG. The PhNR amplitude from the b-wave peak in patients with stage III POAG correlated with the RNFL thickness in the perifovea’s nasal sector (r = 0.51; p < 0.01).

Conclusion. Specific patterns of morphological-functional changes in the parameters of the retina’s inner layers in patients with advanced POAG are presented, which can be used as clinical markers in determining an individual therapeutic strategy. 

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