Histologic validation of optical coherence tomography-based three-dimensional morphometric measurements of the human optic nerve head: Methodology and preliminary results. (April 2021)

• Record Type: Journal Article
• Authors: Fazio, Massimo A.; Gardiner, Stuart K.; Bruno, Luigi; Hubbard, Meredith; Bianco, Gianfranco; Karuppanan, Udayakumar; Kim, Jihee; El Hamdaoui, Mustapha; Grytz, Rafael; Downs, J. Crawford; Girkin, Christopher A.
• Is Part Of: Experimental eye research. Volume 205(2021)
• Publication Date: 2021-04
• Subjects: Optic nerve head morphology and biomechanics -- Glaucoma -- Spectral domain optical coherence tomography -- Histology; SDOCT Spectral domain optical coherence tomography -- ONH optic nerve head -- LEP Living Eye Project -- 3D three-dimensional -- IOP intraocular pressure -- CNS central nervous system -- BSS balanced salt solution -- BM Bruch's membrane -- BMO Bruch's membrane opening -- ASCO anterior scleral canal opening -- ALCS anterior lamina cribrosa surface -- ALCSD anterior lamina cribrosa surface depth -- EDI enhanced depth imaging; Ophthalmology -- Periodicals; Eye -- Periodicals; Œil -- Périodiques; Ophthalmology; Periodicals; Electronic journals; 612.8405
• DOI: 10.1016/j.exer.2021.108475
• Languages: English
• ISSNs: 0014-4835

Abstract

Abstract: Purpose: To compare the three-dimensional (3D) morphology of the deep load-bearing structures of the human optic nerve head (ONH) as revealed in vivo by spectral domain optical coherence tomography (SDOCT) with ex vivo quantitative 3D histology. Methods: SDOCT imaging of the ONH was performed in six eyes from three brain-dead organ donors on life-support equipment awaiting organ procurement (in vivo conditions). Following organ procurement (ex vivo conditions), the eyes were enucleated and underwent a pars plana vitrectomy followed by pressurization to physiologic IOP and immersion fixation. Ex vivo ONH morphology was obtained from high-fidelity episcopic fluorescent 3D reconstruction. Morphologic parameters of the observed ONH canal geometry and peripapillary choroid, as well as the shape, visibility and depth of the lamina cribrosa were compared between ex vivo and in vivo measurements using custom software to align, scale, and manually delineate the different regions of the ONH. Results: There was significant correspondence between in vivo and ex vivo measurements of the depth and shape of the lamina cribrosa, along with the size and shape of Bruch's membrane opening (BMO) and anterior scleral canal opening (ASCO). Weaker correspondence was observed for choroidal thickness; as expected, a thinner choroid was seen ex vivo due to loss of blood volume upon enucleation (−79.9%, p < 0.001). In addition, the lamina was shallower (−32.3%, p = 0.0019) and BMO was smaller ex vivo (−3.38%, p = 0.026), suggesting post mortem shrinkage of the fixed tissue. On average, while highly variable, only 31% of the anterior laminar surface was visible in vivo with SDOCT (p < 0.001). Conclusions: Morphologic parameters by SDOCT imaging of the deep ONH showed promising correspondence to histology metrics. Small but significant shrinkage artifact, along with large effects of exsanguination of the choroid, was seen in the ex vivo reconstructions of fixed tissues that may impact the quantification of ex vivo histoarchitecture, and this should be considered when developing models and biomarkers based on ex vivo imaging of fixed tissue. Lack of visibly of most of the lamina surface in SDOCT images is an important limitation to metrics and biomarkers based on in vivo images of the ONH deep tissues. Highlights: This study presents the first histologic validation of the ONH tissues imaged by OCT. OCT imaging of the deep optic nerve tissues show promising correspondence to ex vivo histology imaging. On average, only 31% of the anterior laminar surface was visible in vivo by OCT imaging compared to histology. On average, anterior laminar surface depth was 30% higher in vivo compared to histology.