Correlation of spectral domain optical coherence tomography and histology in the porcine retina

Abstract

Purpose : Spectral domain optical coherence tomography (SD-OCT) can accurately measure retinal thickness and morphological changes in vivo, facilitating longitudinal studies of age- and disease-related alterations in the retina. To date, the precise correlation of SD-OCT with retinal histology in the porcine retina is lacking. Herein, we studied SD-OCT, histology, and immunofluorescence imaging to correlate the hypo- and hyper-reflective bands observed on SD-OCT with the lamellar architecture and cellular constituents of the porcine retina.

Methods : SD-OCT images of the retina in the domestic pig were acquired with the Heidelberg Spectralis HRA+OCT (3.9-micron axial-resolution, radial scan pattern, 100 images, 1536 axial scans). Histological analysis of the retina with light and electron microscopy was performed using plastic-embedded sections. Cryostat sections of the retina were examined by fluorescence microscopy after alignment with SD-OCT images. Photomicrographs from the histologic sections were linearly scaled to correct for tissue shrinkage and compared with SD-OCT images.

Results : SD-OCT images of the domestic pig retina correlated well with ex vivo histomorphometric data. Plexiform layers were more reflective than nuclear layers. A highly reflective band in the inner nuclear layer (INL) correlated with an interface between the horizontal cells in the outer portion of the INL and the bipolar cells in the inner portion of the INL. The external limiting membrane and inner-outer segment junction were visualized as hyper-reflective bands. The retinal pigment epithelium (RPE) consisted of two distinct hyper-reflective layers: 1) the interdigitation zone between the RPE apical cell processes and outer segments and 2) the outer aspect of the RPE/Bruch membrane complex. With enhanced depth imaging, the choriocapillaris was observed to be a very distinct hypo-reflective layer external to the RPE.

Conclusions : The lamellar structure of the porcine retina imaged with SD-OCT in vivo strongly correlated with ex vivo histological examination. SD-OCT is a valuable, non-invasive tool for in vivo studies of pathophysiologic conditions, including retinal vascular and degenerative diseases, in the porcine model. Investigators seeking a large animal model for translational research or preclinical studies for retinal diseases may now employ this correlative data on SD-OCT and histology of the porcine retina.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.