Vessel Density Loss of the Deep Peripapillary Area in Glaucoma Suspects and Its Association with Features of the Lamina Cribrosa

Abstract

Purpose: To investigate the association of decreased vessel density (VD) in the deep peripapillary region and structural features of the lamina cribrosa (LC).

Materials and methods: 70 eyes of glaucoma suspects with enlarged cup-to-disc ratio were scanned and 51 eyes with adequate image quality were included in this study. All subjects had localized VD defects in the deep layer but intact VD in the superficial layer around the peripapillary region using optical coherence tomography angiography (OCTA). Only single-hemizone OCTA results from one eye of each subject had to fulfill the distinctive feature mentioned above to perform inter-eye and inter-hemizone comparisons. The thickness and depth of the LC, and prelaminar thickness were measured using enhanced depth imaging OCT (EDI-OCT). Paired t-tests were performed to evaluate differences in measurements of the LC and prelaminar thickness within each individual. p-values lower than 0.05 was considered to be statistically significant.

Results: Eyes with deep VD defects in the peripapillary region in OCTA had thinner LC than the fellow eyes. The hemizone with the deep VD defects in the peripapillary region had a thinner LC and a deeper depth of LC than the other hemizone in the same eye. According to logistic regression analysis, a thin LC was a significant factor associated with deep VD defect in the peripapillary region.

Conclusions: Glaucoma suspect eyes with deep VD defects in the peripapillary area exhibited structural differences in the LC. The structural changes of the LC was associated with the vessel density in the deep peripapillary layer at the stage of suspected glaucoma.

Keywords: glaucoma suspect; lamina cribrosa; optical coherence tomography angiography; peripapillary vessel density.

Figure 1

(A) Superficial peripapillary OCT angiography in the superficial layer (from the retinal nerve fiber layer (RNFL) to 130 μm below the internal limiting membrane (ILM) including the ganglion cell-inner plexiform (GCIPL) layer). (B) Deep peripapillary OCT angiography in the deep layer (from 130 μm below the ILM to the basement membrane including the inner nuclear layer (INL)). (C) RNFL OCT and visual field test with increased cup-disc ratio (CDR) which indicate glaucoma suspect. There are subjects among glaucoma suspect patients with wedge-shaped VD defect in the deep layer of peripapillary area (indicated as arrows in B), even though the vessel density in the superficial layer is unaffected (intact vascular status in A).

Figure 2

Scatter plots showing comparisons of the thickness and depth of lamina cribrosa (A) between eyes with deep vessel density (VD) defects and the contralateral eyes with intact VD, and (B) between hemizones with deep VD defects and the other hemizones with intact VD in OCT angiography.

Figure 3

A representative case. (A) A 60-year old woman with decreased deep OCTA vessel density of peripapillary area in her left eye. (B) The thickness of lamina cribrosa in her left eye with abnormal vessel density was thinner than that in her right eye with normal vessel density.

Figure 4

A representative case. (A) A 47-year old man with deep VD defect in his superotemporal peripapillary area of left eye. (B) The lamina cribrosa of his superior half was thinner and more deeply located than that of his inferior half.