Diplophthalmia versus cyclopia and synophthalmia. Mechanisms of doubling of the eye.

In historical and many scientific papers of the 20th century double formation of eyes has been described as cyclopia, which develops as a variably marked fusion of both eye anlagen into a single eye in median position. In contrast with mythology, no cases were viable, as cyclopia is always accompanied by other severe deformities, such as cerebral defects and proboscis. For the first time a double eye on one side - a unilateral diplophthalmia - in a viable child born in Austria is presented after a reviewal of fundamentals of general and experimental embryology, cyclopia and unilateral synophthalmia. Unlike cases of cyclopia with two fused eyes from two anlagen in one single orbit, we found a total of three eyes from two anlagen in two orbits; a normally developed eye in the right orbit and a double eye in the left with no proboscis. In addition porencephaly, a double canine tooth, and a lateral branchial cyst were also present on the left side. An examination of this unique case partially corroberated the findings of experimental embryology as to the normal formation of the lens and brought to light new findings concerning the formation of the vitreous body and the retina, because in the 'extra' left eye a hyaloid artery did not develop. There was only one optic nerve with a normal optic disc as a guiding structure for this artery in the 'normal' left eye.