AIM: To evaluate the rotational stability of a Toric intraocular lens(IOL)using purpose-designed software and to determine the influence of axial length(AL)and in- the-bag IOL alignment on IOL rotation.

METHODS: This study enrolled eyes that had AcrySof toric IOL implantation. The AL was measured using optical coherence biometry or immersion A-scan biometry. Corneal astigmatism was determined by manual keratometry and topography. The IOL alignment was vertical, horizontal, or oblique.Rotational stability was measured using the purpose- designed software, and the mean absolute difference was determined. The effect of AL and IOL alignment on rotational stability was determined 6 months postoperatively.

RESULTS: The study evaluated 168 eyes(168 patients). The mean AL was 24.12±1.62(range 19.33 to 29.04)mm. The median IOL rotation was 0.4 degree from baseline to 1 week, 1.1 degree from 1 week to 1 month, 0.3 degree from 1 to 3 months, and 0.2 degree from 3 to 6 months. The maximum rotation occurred between 1 week and 1 month. There was a strong correlation between AL and IOL rotation at 6 months(r = 0.92, P<0.01). The mean absolute difference at 6 months was not significantly different between the 3 axis placement categories when correlated with the rotation(P=0.102, analysis of variance).

CONCLUSION: Toric IOL rotation is greater in eyes with a longer AL. Alignment of the IOL in the capsular bag have no influence on rotation.