Abstract
Purpose:
Retinal anatomy and layering varies between different species and also between different locations within the same eye. Here we asses such differences with optical coherence tomography (OCT) in three laboratory animal species and correlate the respective reflectivity profiles with the underlying anatomical structures.
Methods:
Spectral-Domain Optical Coherence Tomography (SD-OCT), confocal Scanning-Laser Ophthalmoscopy (cSLO), and Fluorescein Angiography (FA) were performed in mice (Mus musculus), mongolian gerbils (Meriones unguiculatus), and cynomolgus monkeys (Macaca fascicularis). Most images and all of the OCTs were obtained with the Heidelberg Engineering Spectralis system, some of the cSLOs and FAs with the Heidelberg Engineering HRA I. Reflectivity profiles were extracted from 8-bit greyscale OCT images using the ImageJ software package (http://rsb.info.nih.gov/ij/). All procedures were performed in accordance with the local ethics committee and the ARVO statement for the use of animals in ophthalmic and visual research.
Results:
OCT scans were obtained reliably from all three animal species. The respective reflectivity profiles allowed for a quantitative assessment of layer-specific characteristics. In comparison, all layers were present in all species, but varied in their individual properties (relative size and degree of reflectivity). In general, plexiform layers showed a higher level of reflectivity than nuclear layers. Surprisingly, the reflectivity associated with the nerve fibre layer (NFL) was particularly strong. A subtotal reflection was observed in the fovea of the monkey an on the surface of major retinal vessels.
Conclusions:
This study in three laboratory animal species shows the capability of OCT reflectivity profiles to provide a detailed, quantitative description of retinal layers and structures, and allows in particular an in-depth analysis of specialized retinal regions. Our results emphasize the potential of this method in the evaluation of therapeutic strategies.
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
688 retina