Incipient histopathological lesions in citral-induced microphthalmos in chick embryos.

Microphthalmos was indeed experimentally in 3-day-old chick embryos by intraamniotic injection of citral. Various degrees of this particular microphthalmic syndrome were observed. Severe cases were always accompanied by destructive changes in the ipsilateral part of the head. The corneal epithelium lost its continuity and the lens showed, even in the early stages, severe degenerative changes with spherophakia. The neural retina seemed to be affected later and showed hyperplasia and fold formation, while the retinal pigment epithelium was only mildly affected. The mesenchyme behaved differently according to its location: the superficial corneal and ciliary mesenchyme underwent hyperplasia, while the deeper choroidal mesoderm showed edematous changes only. This temporal and spatial distribution of pathological changes in the eye structures favors the assumption that citral acts locally. The experimental microphthalmic syndrome is not only due to the direct effect of the exogenous teratogenic factor on the ocular anlagen but is also the result of subsequent adaptive changes of these structures to the new environmental condition.