Prelaminar Tissue Thickness in Moderate to Advanced Glaucoma

Abstract

Purpose : Most reported information regarding the in vivo prelaminar tissue is based on a limited number of sampling planes on OCT volumes. In this study we used whole volume data to compute a global mean prelaminar thickness and examined its association with structural and functional parameters in subjects with moderate to advanced glaucoma. Given the low reliability of OCT and visual field (VF) to detect progression in advanced subjects, this study focuses on this subset as it could benefit most from a novel structural parameter.

Methods : Subjects with moderate to advanced glaucoma, as indicated by a baseline spectral-domain(SD) OCT’s mean RNFL thickness ≤70μm, were included. All subjects had a baseline prototype swept-source(SS) OCT, VF (Humphrey Field Analyzer, Zeiss), and at least one follow-up SD-OCT (Cirrus HD-OCT, Zeiss). SS-OCT raster scan of the optic nerve head (ONH) (3.5 mmx3.5mm;400x400x861sampling points) was performed. The prelaminar tissue was manually delineated in each SS-OCT cross-section and the mean distance between the vitreous/ONH interface and the anterior lamina surface was automatically computed by averaging the thickness in every sampling point within the ONH. A random mixed effects model was used for assessing the association between baseline prelaminar thickness and cross-sectional variables, and longitudinal changes in structural and functional parameters.

Results : 31 eyes from 27 subjects were available for analysis (mean follow-up=20 months). Baseline prelaminar thickness was positively associated with baseline RNFL (average, superior, inferior), GCIPL (average, superior, inferior), rim area, vertical cup to disc ratio (C/D ratio), VFI and MD (p≤0.02) and negatively associated with baseline average C/D ratio and cup volume (p≤0.002;Table). Longitudinal analysis demonstrated that thicker baseline prelaminar tissue was associated with faster rate of progression for average and inferior RNFL thickness and faster enlargement of average and vertical C/D ratio (p≤0.03).

Conclusions : Prelaminar tissue thickness is significantly associated with ONH, peripapillary, macular and VF parameters on cross-sectional analysis. On longitudinal analysis prelaminar thickness showed association with faster rate of RNFL progression. Thorough sampling of the prelaminar tissue thickness has the potential to serve as a biomarker for both disease status and risk of progression in subjects with glaucoma.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

*Median(1^stquartile,3^rdquartile)