Rate of Retinal Nerve Fiber Layer Thinning in Glaucomatous Eyes With Optic Disc and Parapapillary Deep-Layer Microvasculature Loss

Abstract

Precis: Microvasculature dropout in the parapapillary choroidal layer was a more important biomarker of glaucomatous nerve fiber layer thinning when it presented with deep-layer microvasculature of the optic disc rather than when it presents by itself. Purpose: To characterize open-angle glaucoma (OAG) eyes with optic nerve head (ONH) deep-layer microvasculature dropout (MvD-D) and parapapillary choroidal layer microvasculature dropout (MvD-P) and compare their retinal nerve fiber layer (RNFL) thinning rate. Methods: This study included 122 OAG eyes that underwent ≥5 serial spectral-domain optical coherence tomography (OCT) scans during a mean follow-up of 5.4 years. Swept-source OCT angiography (SS-OCTA) was used to evaluate MvD-P and MvD-D. Subjects were classified into three groups according to the presence of MvD-P and MvD-D: (1) no dropout (n=37); (2) solely MvD-P (n=40), and (3) both MvD-P and MvD-D (n=45). The RNFL thinning rate was compared among the three groups, and the associated factors were assessed by Cox proportional hazard analysis. Results: RNFL thinning rates were highest in the group with both MvD-P and MvD-D, followed by the group with solely MvD-P and finally by the no dropout group (−0.24 vs. −0.65 vs. −1.20 μm/year, P<0.001). Thinner central corneal thickness (hazard ratio [HR]=0.990, P=0.003), presence of disc hemorrhage (HR=1.802, P=0.035), and coexistence of MvD-P and MvD-D (HR=2.941, P<0.001) were the factors associated with RNFL thinning. Conclusions: The coexistence of MvD-P and MvD-D was associated with faster RNFL thinning than MvD-P alone or no dropout, which suggested that observing the optic disc deep microvasculature along with parapapillary choroidal layer using SS-OCTA may be clinically relevant in monitoring glaucoma progression.

Underlying Microstructure of the Lamina Cribrosa at the Site of Microvasculature Dropout

“… 2 , 10 , 19 The optic-disc MvD was accompanied by a MvD-PC in all cases, which has led to suggestions of a pathogenic link between the optic-disc MvD and MvD-PC. 2 , 10 …”

“…Previous studies investigating MvD in the optic disc have utilized the whole-signal mode of OCTA to visualize the intrapapillary MvD. 2 , 10 , 19 The optic-disc MvD was accompanied by a MvD-PC in all cases, which has led to suggestions of a pathogenic link between the optic-disc MvD and MvD-PC. 2 , 10 …”

“…Considering that the normal morphological characteristics of the ONH 23 – 25 and thickness profiles of the PC 26 , 27 differed between the superior and inferior sectors, and that most occurrences of MvD-PC and MvD-LC were located in the inferior sectors, 2 , 10 , 19 only eyes with ONH damage to the inferior sectors were included in the present study.…”

“… 2 , 13 , 19 Only the temporal side of the vertical line passing through the centroid of the optic disc was used in the analysis because the ability to analyze the deep-layer microvasculature at the nasal portion of the ONH is restricted by the overlying neural rim and large vessels. 2 , 10 , 19 , 31 Two observers (YJR, DKH) independently identified MvDs while masked to the clinical information of the subjects. Disagreements between these observers were resolved by a third adjudicator (EJL).…”

“… 2 Progressive retinal nerve fiber layer (RNFL) thinning occurred more rapidly when MvD-PC was accompanied by optic-disc MvD. 10 However, the pathogenic mechanisms of optic-disc MvD and its relationship with MvD-PC remain poorly understood.…”