Reduction of Astigmatism after Keratoplasty

Inquiries to Stuart I. Brown, M.D., Dept. of Ophthalmology, University of California, Sm; Dieyo, T-014, La folia, CA 92093. Recently, postcorneal transplant astigmatism was reported to be reduced to 2.6 diopters by the use of eight 10-0 nylon interrupted sutures and a continuous 11-0 nylon suture. How­ ever, Heidemann and associates used a similar technique and found increased astigmatism. We report astigmatism in 25 cases averaging less than 1.5 diopters with a combination of 12 interrupted 10-0 nylon sutures and a continu­ ous 11-0 nylon suture. Twenty-five corneal transplants were per­ formed between November 1984 and May 1986 by one of us (S.I.B.). Excluded from this study were heavily vascularized corneas, and corneas with perforations or congenital opacities. The patients were followed up for three and 21 months postoperatively. Removal of interrupt­ ed sutures was begun eight to 12 weeks postop­ eratively in the meridian of greatest keratometric astigmatism. Suture removal continued weekly until satisfactory astigmatism was achieved. Spectacles were prescribed after sta­ ble keratometry on two separate occasions. All corneas remained transparent. No wound elevations or separations occurred. The mean corneal astigmatism was 1.37 diopters ± 0.24 (S.E.M.). Fourteen eyes had 1.25 diopters or less of corneal astigmatism (Fig. 1). The mean refractive astigmatism was 1.52 ± 0.18 diopters (Fig. 2). Fourteen of 24 eyes achieved best corrected visual acuity of 20/40 or better. The remainder of the eyes had varying degrees of macular pathology. To date, one patient has had a broken 11-0 nylon suture 14 months postoperatively, which caused a 2.5-diopter change of astigmatism. Her astigmatism was reduced by removing the remaining interrupt­ ed sutures in the steep meridian. The results of this series support earlier stud­ ies indicating that the combination of inter­ rupted sutures with a continuous suture fol­ lowed by removal of the interrupted sutures in the steep meridian results in a reduction of astigmatism after corneal transplantation. The use of 12 interrupted sutures was initiated after observing graft overriding in two consecutive eyes in which eight sutures were utilized. This use of 12 interrupted sutures achieved more precise correlation with the steep meridian and resulted in the lowest published postkeratoplasty astigmatism. These results were consis­ tent; the majority of cases had 1.25 diopters or less of corneal astigmatism. This technique also allowed for early reliable postoperative refractions, usually by week 14. The refractive errors remained stable through­ out the follow-up period of this study except for the one patient described above. The obser­ vations of an increase in astigmatism after con­ tinuous suture disruption at 14 months indi­ cates that the wounds may not be stable for prolonged periods. The use of an 11-0 suture of a stronger and longer lasting material may be indicated. We believe that the minimal irregu­ lar astigmatism, with the resulting excellent and stable visual acuity, is related to the care taken not to tie tightly the continuous or inter­ rupted sutures. Consequently, there was mini­ mal flattening of the graft and minimal ir­ regular astigmatism before removal of the