Soemmering's ring and its dislocations.

In extra-capsular extraction of cataract in which the central portion of the anterior capsule is removed, or in injury of the lens, or in discission operations in which the anterior capsule is torn and the central portion of the lens substance is penetrated and becomes absorbed, a greater part of the capsule sac remains intact. According to Wessely (1910), when the central part of the anterior capsule is opened up, it then loses its stretching capacity and collapses, forming at first a flat ring. Now filaments of the lens substance frequently remain at the equator of the capsule sac; with this also remain parts of the lens nucleus and subcapsular epithelium. The torn anterior capsule then becomes retracted and adheres to the posterior capsule at the margin, so that the remains of the lens fibres cannot be absorbed and therefore form a ring of folded capsule. The epithelial cells can grow in this ring and, associated with the deposition of hyaline capsular material in the remains of the lens substance, a swollen ring or cushion is formed. This ring, remaining hidden behind the iris and being held in position by the zonule of Zinn, cannot be seen in the ordinary eye. There is also practically no disturbance of vision when the ring hangs in its original position, because the central portion always remains clear. When operative treatment for high myopia was in vogue, such ring formations were not uncommon. The procedure known as Fukala's operation had as its first step the discission of the lens; the swollen lens material formed as the result of discission was then washed out, and in most cases parts of the anterior and posterior capsule with remains of lens fibres and subcapsular epithelium were left behind and formed a swollen ring. This ring in its typical form can also arise after discission of congenital cataract.