Keratoconus keratoplasty curvatures and contact lens wear

SUMMARY Fifty-three grafted keratoconus corneas chosen at random from several hundred operated upon over a 10-year period showed an increase in myopia after removal of sutures but a decrease in astigmatism. With the photoelectrokeratograph machine the spherical zone was shown to be limited to 3 mm with gross eccentricities. Half the patients chose to wear contact lenses after surgery and 10 % had no correction. Contact lens wearers showed a much greater decrease in astigmatism than spectacle wearers. The treatment of keratoconus by keratoplasty would be ideal if the curvatures of the donor graft resulted in an emmetropic eye. But for several reasons this is rarely possible. The chief reasons given are light transmission defects of the graft tissue or irregulari-ties in curvature of the donor corneal surface. Analysis of curvatures even suggested to previous workers that keratoconus recurs in the grafted eye. It will not be the purpose of this paper to discuss light transmission problems, which are chiefly concerned with endothelial survival and function, or the several problems that iesult in opacities, either partial or total, of the graft. The latter are usually associated with either inflammatory reactions of healing or immunological reactions. The various aspects of graft size, shape, and suturing techniques have been dealt with by several workers. The conclusions so far are that, while size and shape may alter the final curvature (Ruben, 1972; Troutman and Meltzer, 1972; Troutman, 1973), the reasons why they do so are not fully known. According to Ruben (1972) the relationship between average keratometry and size was related to graft size; thus the large grafts resulted in overall flatter curvatures. Recent work by Davies et al. (1976) disputes a statistical relationship between number of sutures but favours more the tension present in sutures. Indeed, it is well known that the tension, when released on removal of sutures even one-and-a-half years after grafting, results in sudden changes of graft curvatures. This has led some surgeons to leave graft sutures of 10-0 Perlon i