Correlation of in vivo ultrahigh–resolution Optical Coherence Tomography with histological sections in non–human primate eyes

Abstract

Abstract: : Purpose: Deliniation and quantification of intra– and subretinal layers in eyes of non–human primates applying in vivo ultrahigh–resolution optical coherence tomography (uhrOCT) and correlation with corresponding histological section of the same eyes. Methods: A series of in vivo uhrOCT cross–sectional images (approx. 3 µm axial resolution) of the macula and optic nerve were obtained in 3 eyes of 3 cynomolgous monkeys horizontally and at ± 15° orientation. Decision to euthanize the animals was taken for reasons independent of the aims of the present study. The animals were anesthetized during the experiment and the ARVO guidelines for the Use of Animals in Ophthalmic and Visual Research were followed. At the end of the experiment animals were sacrificed and the examined eyes were enucleated. Prior to enucleation 2 sutures were performed nasally and temporally on the globe to mark the orientation of the eye for subsequent histological sectioning. After fixation in a modified Davidson solution for 48 hours the eyes were cut and embedded in paraffin. A series of consecutive histological sections (10 micron thickness) were obtained spanning the optic nerve and the macula area. Corresponding OCT and histological sections were identified, aligned and compared. Results: Corresponding ultrahigh–resolution OCT and histology sections could easily be identified in all assessed eyes. Axo–dendritic layers (nerve fiber layer, inner and outer plexiform layer) were more reflective than cell body layers (ganglion cell layer, inner and outer nuclear layer). The thicknesses of the different intra– and sub–retinal layers delineated in the uhrOCT data corresponds well to the respective histological data. Little geometrical correction (mainly in the distal part, especially the photoreceptor layer) was necessary to compensate for alterations due to embedding and sectioning artifacts. Conclusions: In vivo uhrOCT correlates well with histology performed in the same eye, allowing delineation and quantification of intra– and sub–retinal layer thickness and therefore providing a basis for improved interpretation of in vivo ophthalmic uhrOCT tomograms of high clinical relevance. Hence, uhrOCT allows for reliable visualization and measurement of intra–retinal layers in vivo, facilitating early ophthalmic diagnosis and better understanding of disease pathogenesis.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • pathology: experimental