Further studies on the ridge at the internal edge of the cataract incision.

A pathologic and experimental study of the etiology and morphology of the ridge, visible gonioscopically in the region of the internal lips of the cataract incision during and after the cataract operation, is described. The ridge observed clinically cannot be reproduced in human eye-banks eyes but can be reproduced in vivo in the eye of the owl monkey. Histopathology and ultramicroscopic studies of these experimental eyes, together with evidence derived from histopathologic slides of postmortem human eyes, suggest that the ridge is probably the result of immediate edematous swelling of the deeper layers of the corneal stroma after the incision transects corneal endothelium and the Descemet membrane. While internal wound lip malapposition may be a contributing factor to formation of the ridge, it is probably not an essential component. The ridge is not caused by the incision-closing sutures for it is already present prior to suturing of the wound. The role in ridge formation of mechanical stress alterations produced immediately by the incision is considered but is not known.