The effect of selective suture removal on astigmatism following penetrating keratoplasty.

We retrospectively evaluated selective removal of interrupted nylon sutures to reduce astigmatism following penetrating keratoplasty in 68 eyes with eight or 12 interrupted sutures and one running suture. Following removal of one to four interrupted sutures at one visit (N = 234 visits), corneal astigmatism had changed 2 to 3 diopters (range 0 to 12 D) by the next visit. The astigmatism decreased greater than or equal to 1 D in 54%, changed 0 to .87 D in 28%, and increased greater than or equal to 1 D in 18%. When a total of five or six sutures were removed during the 5 months following surgery, less than 3 D of residual astigmatism was present in 50 eyes (74%). The axis of astigmatism changed less than or equal to 40 degrees in 74% (n = 65). In a second group of 20 eyes with double running sutures, removal of the 10-0 running suture in all 20 eyes produced an average change of 1.8 D (range = 0 to 3.75 D), with an equal number of increases and decreases. Vector analysis showed the total induced change in astigmatism was approximately twice the absolute keratometric change.