Retrocorneal membranes. II. Factors influencing their growth.

DURING our recent studies on the origin of retrocorneal membranes, from which it was concluded that these structures are errant stromal scar tissue, we became increasingly aware that certain conditions of the cornea, other than mere perforation of the Descemet's and endothelial layers, had to be satisfied before these membranes would develop.Three such conditions presented themselves:(1) That the corneal stroma be in a relatively healthy state and capable of regenerating excess scar tissue;(2) That the perforation in Descemet's membrane be wide enough to permit the protrusion of this scar tissue into the anterior chamber;(3) That the endothelium be damaged or absent from the wound margins allowing a sufficient period of time for errant stromal scar tissue to form before complete endothelial repair is accomplished.It was felt that if these primary conditions were indeed necessary, preventive measures could perhaps be taken before and during penetrating corneal s urgery to reduce the incidence of post-operative retrocorneal membranes.Therefore, observations of human and rabbit specimens, and experimentation on the latter were undertaken to test the validity of each of the suggested conditions. MethodThe histological appearance of serial paraffin sections of human corneal buttons removed at keratoplasty at the Queen Victoria Hospital, East Grinstead, and rabbit corneas in which perforations in Descemet's membrane and endothelium had been produced experi- mentally, were used as follows:Condition 1 26 human corneal buttons.with perforations in Descemet's membrane and the endo- thelium caused by previous penetrating keratoplasty in thirteen cases, accidental mechanical trauma in two, and degenerative changes in eleven, were carefully examined, and the histological condition of the stroma was related to the extent of any retrocorneal membrane present, and to the observable effects of Conditions 2 and 3. Condition 2The human specimens, above, were examined and the dimensions of the perforations in Descemet's layer related to the extent of any retrocorneal membrane and to Conditions 1 and 3.Similar observations were made upon sixteen rabbit corneas, in which Condition 1 was