Volumetric subfield analysis of cynomolgus monkey’s choroid derived from hybrid machine learning optical coherence tomography segmentation

Abstract

This study aimed to provide volumetric choroidal readings regarding sex, origin, and eye side from healthy cynomolgus monkey eyes as a reference database using optical coherence tomography (OCT) imaging. A machine learning (ML) algorithm was used to extract the choroid from the volumetric OCT data. Classical computer vision methods were then applied to automatically identify the deepest location in the foveolar depression. The choroidal thickness was determined from this reference point. A total of 374 eyes of 203 cynomolgus macaques from Asian and Mauritius origin were included in the analysis. The overall subfoveolar mean choroidal volume in zone 1, in the region of the central bouquet, was 0.156 mm3 (range, 0.131–0.193 mm3). For the central choroid volume, the coefficient of variation (CV) was found of 6.3%, indicating relatively little variation. Our results show, based on analyses of variance, that monkey origin (Asian or Mauritius) does not influence choroid volumes. Sex had a significant influence on choroidal volumes in the superior-inferior axis (p ≤ 0.01), but not in the fovea centralis. A homogeneous foveolar choroidal architecture was also observed.

Cynomolgus monkey’s retina volume reference database based on hybrid deep learning optical coherence tomography segmentation

“…In the choroid layer, in contrast, only sex had a significant influence on choroidal volumes but not origin 11 . Interestingly, the effect of sex appears to be different in the choroid and in the retina.…”

“…2 , 3 and 4 . For ease of comparison, the boxplots also contain the data of the corresponding choroidal volumes, which was obtained in a previous study from the same eyes of the same individuals 11 . The results are depicted in the following figures:

Figure 2 Boxplots of zone volumes.

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“…The origin had a significant effect on S1, S4, and S5. For ease of comparison, rows six to nine of Table 7 contain the results of the statistical hypothesis tests based on an equivalent ANOVA performed on the choroid volumes 11 .…”

“…This study was conducted to provide a reference database for OCT cynomolgus monkey retinal volumes, which depend on the origin, sex, and eye laterality. Moreover, this study compares the results obtained for the retinal volumes to results obtained for the choroidal volumes, which are based on the same OCT scans of the same cynomolgus monkeys and were published in a previous choroid study 11 .…”

“…Therefore, the animals’ geographic origin may play a crucial role in neuroretinal development. Moreover, knowledge of these natural variations in retinal morphology, such as retinal thickness and vessel parameters 11 , 12 , is vital when planning the study design and assessing retinal thickness measurements from cynomolgus monkey’s retina to prevent misinterpreting the natural variations with suspected retinal pathology.…”