EFFECT OF INCISION LOCATION ON PREOPERATIVE OBLIQUE ASTIGMATISM AFTERSCLERAL TUNNEL INCISION

Purpose: To evaluate the effect of incision location on clinically rel evant preoperative oblique astigmatism. Setting: Department of Ophthal mology, Virchow Medical Center, Humboldt-University, Berlin, Germany. Methods: This prospective study included 63 patients who had phacoemul sification and posterior chamber intraocular lens implantation using a standardized 7.0 mm self-sealing trapezoidal scleral tunnel incision. Each patient was randomly assigned to one of three incision locations : Group A, conventional superior incision; Group B, temporal incision; Group C, oblique incision centered on the steeper meridian (modified BENT incision). Astigmatism analysis was performed by manual keratomet ry and corneal topography. Results: A significant mean reduction in as tigmatism of 0.58 diopter (D) (P < .01) was achieved in only the modif ied BENT incision group. Postoperatively, significant flattening of 0. 27 D (P < .01) in the steeper meridian as well as steepening of 0.29 D (P < .01) in the flatter meridian occurred. No decrease in astigmatis m was noted in the superior or temporal incision groups. Five months p ostoperatively, vector analysis showed that surgically induced astigma tism was significantly higher in the superior incision group (1.16 D /- 0.44 [SD]) than in the temporal incision group (0.66 +/- 0.32 D) or modified BENT incision group (0.82 +/- 0.50 D). Corneal topographic a nalysis confirmed these results within +/- 0.3 D. Conclusions: Only th e oblique incision centered on the steeper meridian (modified BENT inc ision) effectively and predictably reduced preoperative oblique astigm atism. In eyes with clinically relevant oblique astigmatism, we recomm end using a modified BENT incision.