P 259
Does change in astigmatism after phacoemulsification depend on the position of the incision?J. Gruber, M. Mertz, I. M. Lanzl
Introduction: In the context of the modern astigmatism-neutral cataract surgery wound position is propagated to be placed according to preoperative astigmatism. If the wound is situated in the steep meridian of the preoperative astigmatism there should be an induced reduction of astigmatism by flattening the cornea. Whether this plays a role for the benefit of the patient in the conditions of an academic teaching hospital is to be examined in the present study.
Methods: 100 patients undergoing uncomplicated phacoemulsification were retrospectively examined. Surgery was performed by 4 different surgeons in training. The position of the wound was determined independently from the preoperative position of astigmatism according to the preference of the operating surgeon either temporally at 0°or at 90°. The postoperative refraction was performed six weeks or longer after surgery.
Results: 18% of patients presented with a preoperative astigmatism of a mean of -0.75 dpt at 0°. Of those two thirds were operated on with an incision at 90° and one third at 0°. In 2 patients the astigmatism was reduced with no change in axial position with an incision at 0° and in 2 patients the astigmatism increased while maintaining the axis with an incision at 90° as expected. 12% of patients experienced various unexpected changes in the postoperative amount and axial position of their astigmatism. 60% of patients presented with a preoperative astigmatism of a mean of -1.0 dpt a 90°. Of those 8 patients experienced a reduction of the astigmatism with the incision site at 90° and 5 experienced an increase in astigmatism amount with the same incision position. Only 7 patients experienced as expected, an increase of astigmatism amount at the same axial position of 90° when incision was performed at 0°, whereas 7 others encountered a reduction of their astigmatism at 90° when the cut was made at 0°.
Discussion: Overall only 26% of our patients demonstrated a change in astigmatism as expected by the idea of flattening the steep meridian with the incision. In our case this means that under the conditions of cataract surgery in a teaching environment with varying surgeons and varying quality of incision and varying incision distance from the limbus, the most crucial issue for the visual outcome of cataract surgery is to choose the incision site for the comfort of the surgeon in order to reduce possible intraoperative complications. The astigmatism reduction is to be regarded as secondary question. This is in particular the case, if the preoperative astigmatism is only relatively small, as this was the case in our patient population.
Augenklinik der TU München, Ismaninger Str. 22, D-81675 München