[16–20] In our review scleral hyperpigmentations were the most common finding (Figure 2, left). Slightly less frequent were oil-drop like pigment accumulation in the opaque limbus and pigment ...

Article #19-11410: "Scleral pigmentation leads to conspicuous, not cryptic, eye morphology in chimpanzees," by Juan Olvido Perea-García, Mariska E. Kret, Antónia Monteiro, and Catherine Hobaiter.