Intra-ocular pressure in the donor eye and consequent shape of corneal disc margin.

IN over 100 corneal grafts carried out in this clinic from 1960 to 1966, it was found that the edges of the donor discs varied in shape when observed from the side, and these variations were of sufficient clinical importance to determine the success of the results, the best grafts being those with clean-cut straight edges. These observations led us to seek a procedure whereby the desired shape of the donor graft edge could be ensured. Barraquer Moner (1955) noted irregularities of the graft edge and suggested that another disc should be cut if the first was uneven. Pierse (1959) noted that, even with the sharpest trephine, the corneal curvature would be flattened while the disc was being cut, and that this produced a trephine hole in which the edges shelved inwards. He found that a lower intra-ocular pressure in the donor eye produced an even greater shelving and while an increased intra-ocular pressure produced by pressure on the outside of the eye resulted in straight sides. He tried to maintain the shape of the cornea while cutting a donor disc by using the plunger of the trephine as a suction cup. Michaelson (1954) found that the sides of a corneal graft were vertical if it was cut from the endothelial surface, or when the donor eye was held with a firm pressure. He did not specify the equal distortion produced by too much as well as by too little pressure. Gorgiladze (1960a) suggested that the best donor disc was got by using Filatov's method of withdrawing the fluid from the anterior chamber before cutting the graft, andagain cutting from the epithelial surface. He later (1960b) concluded that cutting from the endothelial surface had no advantages, but stated that the best disc edges were got with an intra-ocular pressure of 50-60 mm. Hg; pressures of 8-15 mm. Hg gave edges bevelled towards the inside, and a pressure as high as 200 mm. Hg again distorted the edges.