[4] Some extreme cases of cyclopia have been documented in farm animals (horses, sheep, pigs, goats, and sometimes chickens).

[6] One highly teratogenic alkaloid toxin that can cause cyclopia is cyclopamine or 2-deoxyjervine, found in the plant Veratrum californicum (also known as corn lily or false hellebore).

[7] Cyclopia occurs when certain proteins are inappropriately expressed,[8] causing the brain to stay whole, rather than developing two distinct hemispheres.

[10] Although not proven, it is thought that SHH emitted from the prechordal plate suppresses Pax6, which causes the eye field to divide into two.

If the SHH gene is mutated, the result is cyclopia, a single eye in the center of the face (Gilbert, 2000).