The ecosystem of the ocular microenvironment may be suitable for tumour emboli due to the presence of various immunosuppressive factors, which limit or suppressive inflammation, such as transforming growth factor beta (TGF-b), alpha-melanocyte-stimulating hormone (a-MSH), vasoactive intestinal peptide (VIP) and indoleamine 2,3-dioxygenase (IDO), of which may offer immune detection avoidance (Qu et al. 2021a, b). Here, VIP is linked to neoplasm.