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 astigm atism following phacoemulsification over a period of 3 months is deter mined. Methods: Twenty-two patients who underwent uncomplicated 3.2 mm clear corneal phacoemulsification with foldable Allergan silicone int raocular lens implantation were autorefracted pre-operatively and on d ay 1, week 1, week 6 and at 3 months. The variation in induced astigma tism was analysed using the subtraction method and vector analysis. Th e change in direction of the cylindrical axis was examined. Results: T he induced astigmatism represented by the total vector on day 1 was 1. 17 D and vector decomposition ratio, ATR:WTR (against-the-rule:with-th e-rule), was 21.05:78.95. The total vector increased by 0.5 D in the f irst 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 swin g towards the corneal section meridian on day 1 and to oscillate aroun d that meridian at week 1 and week 6. By 3 months the direction revert ed to that pre-operatively, in most cases. Conclusions: The single-ste p, self-sealing clear corneal section is mechanically stable and, thou gh there is some variability in the measured astigmatism, there is an acceptable functional result throughout the post-operative period.