Relationship between macular intercapillary area measured by optical coherence tomography angiography and central visual field sensitivity in normal tension glaucoma

Purpose To investigate the relationship of macular intercapillary area (ICA) with macular ganglion cell-inner plexiform layer (GCIPL) thickness and central visual field sensitivity (CVFS) in normal tension glaucoma (NTG). Methods Seventy-eight early NTG eyes, 33 moderate-to-severe NTG eyes and 75 normal control eyes were cross-sectional evaluated. All participants underwent swept-source optical coherence tomography angiography (OCT-A; DRI-OCT, Topcon, Tokyo, Japan). A customised MATLAB program was used to quantify macular OCT-A metrics at central 3x3 mm macular region including vascular density (VD), foveal avascular zone (FAZ) area, 10 largest ICA including FAZ area (ICA10_IncFAZ) and excluding FAZ area (ICA10_ExcFAZ). Generalised estimating equation regression models were performed to determine the relationships of OCT-A vascular metrics with GCIPL thickness in the macular region and CVFS. Results NTG eyes had lower global VD, larger ICA10_IncFAZ, and larger ICA10_ExcFAZ than normal controls (all p <= 0.016). In the multivariable analyses, decreased VD (beta=-0.304, p=0.006) and increased ICA (beta=-0.231 for ICA10_IncFAZ and beta=-0.259 for ICA10_ExcFAZ, all p <= 0.042) were significantly associated with decreased GCIPL thickness in early NTG eyes but not in moderate-to-severe NTG eyes. ICA enlargement was associated with CVFS in early NTG eyes (beta=-0.310, p=0.009), while VD was associated with CVFS in moderate-to-severe NTG eyes (beta=-0.272, p=0.038). Conclusion ICA enlargement could be a potentially important disease marker of early NTG as reflected by its association with GCIPL thinning and decrease CVFS specifically for early NTG eyes.