Structure-function Relationship in Advanced Glaucoma After Reaching the RNFL Floor

Abstract

To investigate the relationship between the central visual field (VF) and macular parameters obtained from spectral-domain optical coherence tomography (SD-OCT) in patients with advanced glaucoma that reached the cpRNFL thickness measurement floor and to determine whether the structural changes measured by SD-OCT are useful for estimating the functional status in these patients. A total of 68 eyes from 68 patients with advanced glaucoma were included. Only eyes having an average cpRNFL thickness of ≤57 μm that reached the measurement floor were included. Macular imaging using Cirrus SD-OCT and 10-2 Humphrey VF was performed. The VF mean deviation was converted to a linear scale using unlogged 1/Lambert values. The relationships between the central VF and various macular parameters were determined. Patients had a mean VF mean deviation of -20.69 dB and an average cpRNFL thickness of 51.76±3.61 μm. Correlations between the VF and all cpRNFL thickness parameters were not significant. However, significant correlations were found between the central VF and superonasal macular ganglion cell-inner plexiform layer thickness (r=0.334; P=0.003), inner nasal macular thickness (r=0.301; P=0.013), and outer nasal macular thickness (r=0.331; P=0.007). Even after the cpRNFL had reached the measurement floor, several macular parameters showed a statistically significant relationship with functional status in VF. In particular, the assessment of structural changes in the nasal macular region may be important in determining the central VF in advanced glaucoma.