The effect of scleral fixation ring placement and trephine tilting on keratoplasty wound size and donor shape.

To examine the effect of trephine tilting and scleral ring placement on wound size, five corneas from McCarey-Kaufman medium and ten whole eyes were trephined centrally under controlled conditions and the major and minor axes measured. It was found that, even with great care taken to hold the trephine perpendicular to the cornea, a fair amount of disparity between the major and minor axes of the donor tissue was seen. The scleral fixation ring produced much distortion, although removal allowed the peripheral cornea to return to more normal configuration. The relationship between amount of trephine tilting and increase in the major axis of the cornea is examined, and all of these concepts are discussed in terms of current keratoplasty technique.