embryotoxon /em·bryo·tox·on/ (em″bre-o-tok´son) a ringlike opacity at the margin of the cornea.
anterior embryotoxon embryotoxon.
posterior embryotoxon a developmental anomaly in which there is a ringlike opacity at Schwalbe's ring, with thickening and anterior displacement of the latter; it is seen in Axenfeld's syndrome and Rieger's syndrome.
| anterior embryotoxon n. See arcus cornealis. |
corneal arcus
A greyish-white ring (or part of a ring) opacity occurring in the periphery of the cornea, in middle and old age. It is due to a lipid infiltration of the corneal stroma. With age the condition progresses to form a complete ring. That ring is separated from the limbus by a zone of clear cornea. The condition can also appear in early or middle life and is referred to as arcus juvenilis (or anterior embryotoxon); it is somewhat whiter than corneal arcus. Arcus juvenilis is often associated with heart disease in men (Fig. C19). Syn. arcus senilis; gerontoxon. See marginal furrow.
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Fig. C19 Advanced corneal arcus
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