Variation in astigmatism following the single-step, self-sealing clear corneal section for phacoemulsification

Purpose: A single-step, self-sealing, 3.2 mm clear corneal section is described and the incidence and variation of surgically induced astigmatism following phacoemulsification over a period of 3 months is determined. Methods: Twenty-two patients who underwent uncomplicated 3.2 mm clear corneal phacoemulsification with foldable Allergan silicone intraocular lens implantation were autorefracted pre-operatively and on day 1, week 1, week 6 and at 3 months. The variation in induced astigmatism was analysed using the subtraction method and vector analysis. The change in direction of the cylindrical axis was examined. Results: The induced astigmatism represented by the total vector on day 1 was 1.17 D and vector decomposition ratio, ATR:WTR (against-the-rule:with-the-rule), was 21.05:78.95. The total vector increased by 0.5 D in the first week and then stabilised. Vector decomposition showed an against-the-rule astigmatic drift so that by 3 months the ATR:WTR was 40.49:59.91. There was a tendency of the axis of the negative cylinder to swing towards the corneal section meridian on day 1 and to oscillate around that meridian at week 1 and week 6. By 3 months the direction reverted to that pre-operatively, in most cases. Conclusions: The single-step, self-sealing clear corneal section is mechanically stable and, though there is some variability in the measured astigmatism, there is an acceptable functional result throughout the post-operative period.