The efficacy of a single continuous nylon suture for control of post keratoplasty astigmatism

Purpose: Post operative adjustment of a single continuous suture is an effective means of reducing post keratoplasty astigmatism. This study evaluates post keratoplasty keratometry following suture adjustment with an adjusted suture in place and after the suture is removed. Methods: Average keratometric astigmatism was measured over 24 months time in 26 patient with an adjusted continuous suture and 24 patients with a continuous suture that was not adjusted. Average keratometry in 43 patients with an adjusted continuous suture was compared with 37 patients with combined continuous and interrupted sutures. Finally suture out astigmatism in 19 adjusted patients was compared to six patients with no adjustment. Results: There was increase in average corneal astigmatism over two years of 2.2 diopters in the adjusted group and 1.7 diopters in the non-adjusted group with sutures in place. One year following surgery, average keratometry flattened from 47.5 to 42.9 diopters in the adjusted continuous group and from 47.0 to 46.0 diopters in the group with combined continuous and interrupted sutures. Following suture removal, average astigmatism in patients who had suture adjustment was 4.4 diopters ±2.5 diopters (range 1-10 diopters), and 6.01 diopters (range 4-7) in the non-adjusted group. Conclusions: Average post keratoplasty astigmatism increases after a continuous suture is adjusted but the increase is comparable to patients with acceptable astigmatism who do not require adjustment. More progressive corneal flattening over 12 months time is seen with a continuous suture than with combined sutures. Average suture out astigmatism was 4.0 diopters following suture adjustment, compared to an average of 8.4 diopters prior to adjustment.