Multimodal imaging of the retina and choroid in healthy Macaca fascicularis at different ages

The aim of this study was to identify the morphological features of the retina and choroid in Macaca fascicularis of different ages using multimodal imaging.

A total of 27 Macaca fascicularis with no ocular diseases were studied (mean age, 104.2 months; range, 1.2–223.6 months). Multimodal imaging was obtained from each subject. The morphological features were compared within four subgroups according to age.

On spectrum-domain optical coherence tomography (SD-OCT), four hyper-reflective bands could be observed in the outer retina in non-infant macaques (21/21, 100%), while the interdigitation zone could not be observed in the six infant macaques. A narrow hypo-reflective band just posterior to the retinal pigment epithelium (RPE) was noted in most eyes (25/27, 92.6%). The choroidal–scleral junction (CSJ) was visible in 83.3% of infants but only in 12.5% of adults and 14.3% of the geriatric population, and it could not be seen in juveniles. There was a significant difference in CSJ visibility between the infant group and the other three groups (P < 0.001). Tessellated fundus, in which the choroidal vessels are visible through the retina, could be observed clearly with near-infrared reflectance imaging (NIR). Some granular spots were noted in juveniles, and they accumulated dramatically with age, but were absent in infants.

Notable morphological features can be observed in the Macaca fascicularis subjects using multimodal imaging, and these features vary distinctly according to their age. It is important to note that infant macaques had no interdigitation zone, while the other macaques had no visible CSJ but did have well-defined choroidal capillaries. Age and the features should be considered seriously in future animal studies.