This condition causes abnormally small eyes (globus, e.g. eye ball), as well as other developmental eye defects in dogs. This group of eye defects is known as "MAC" - microphthalmia, anophthalmia, and coloboma, are primarily caused by an absence of vitamin A. According to the researchers, "two hits, maternal and fetal homozygous RBP4 mutations, are evidently needed to reduce vitamin A levels below the threshold for phenotypic expression in offspring." (Haukonen et al, 2018) Severity can vary, but all contribute to blindness in one or both eyes, from birth. Disease is only expressed when both dam and offspring are deletion homozygotes.