Arcuate Relaxing Incisions Guided by Corneal Topography for Postkeratoplasty Astigmatism

Abstract

Purpose: To determine if using corneal topography for planning arcuate relaxing incision placement for postkeratoplasty astigmatism improves clinical results. Methods: Twenty-six eyes with high levels (>5 diopters [D]) of postkeratoplasty astigmatism were studied in a nonrandomized, retrospective, observational case series. Relaxing incisions were placed in the peripheral graft in each steep topographic hemimeridian. The following data were measured: keratometric, topographic, and refractive vector analysis; nonvector astigmatism reduction; surface regularity and asymmetry (surface regularity index and surface asymmetry index); topography patterns; surgical design; and visual acuity. Results: Topographic analysis changed some aspect of the surgery in 51/52 incisions with a 15.7° mean change in incision location. The mean vector correction index (CI) was 0.89 to 0.92 for keratometric, topographic, and refractive indices. Sixty-five percent of eyes had surgically induced astigmatism (SIA) values within 2 D of the surgical goal. Eighty-one percent of eyes had at least a 50% reduction in net astigmatism and 85% had ≤3-D residual refractive cylinder. The mean logMAR visual acuity increased 2 lines. The preoperative and postoperative spherical equivalent showed a high correlation (ρ = 0.914, P = 0.000). The correlation between SIA and targeted induced astigmatism (TIA) was 0.56 (P = 0.003). There was a significant improvement in surface regularity index (P = 0.000) and surface asymmetry index (P = 0.05) values. No statistically significant correlations were found between total incision length and SIA or TIA, or between TIA and correction index. All patients had symmetric (58%) or asymmetric (42%) bowtie topographic patterns preoperatively with 35% achieving round/oval patterns postoperatively. Conclusions: Topography-guided relaxing incision offers an easy method to plan surgery and has some limited advantages over conventional techniques.