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J.C. Merriam, L. Zheng, J.E. Merriam; Does a 2 .6 mm Incision Cause Less Surgically–Induced Astigmatism (SIA) than 3.0 to 4.0 mm Incisions? . Invest. Ophthalmol. Vis. Sci. 2004;45(13):311.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To compare SIA following a temporal 2.6 mm corneal incision to SIA following phacoemulsification with 3.0 to 4.0 mm corneal incisions. Methods: This is a retrospective study of SIA after inserting 3–piece acrylic and silicone IOL’s with a lens forceps and a one–piece acrylic IOL with an injector. To insert the 3–piece IOL’s the initial temporal 2.75 mm corneal incision was enlarged to 3 to 4 mm to accommodate an acrylic IOL with a 6.0 mm optic (Acrysof MA60AC, n = 81), an acrylic IOL with a 5.5 mm optic (Acrysof MA30BA, n = 172), or a silicone IOL with a 6 mm optic (AMO SI40, n = 103). The one–piece acrylic IOL with a 6.0 mm optic (Acrysof SA60AT, n = 125) was injected through a 2.6 mm incision. Unoperated eyes (n=134) from these surgical groups served as controls. We compared groups by calculating SIA with vector analysis, and by comparing absolute change on the horizontal and vertical meridians of each group. All groups were followed for at least 18 months. Results: A linear equation (y = a + bx) described SIA determined by vector analysis, as well as change on the horizontal and vertical meridians of the cornea. Best–fit parameters and the 95% confidence interval were calculated for the observed changes in each group. No consistent effect of IOL type or incision size was detected, and surgical groups did not differ from each other or control eyes. Conclusions:IOL optic thickness and diameter influence minimum incision size when an IOL is inserted with a forceps. In general, the enlarged incision for the 6.0 mm acrylic 3–piece IOL is slightly larger than that for a 5.5 mm acrylic IOL or a 6.0 mm silicone IOL; and all incisions for the three–piece IOL’s are larger than 2.6 mm. However, SIA after these incisions is small, and all incisions appear to be astigmatically neutral. The clinician may prefer the smallest possible incision to maintain a stable chamber and to hasten recovery, but there is no detectable advantage of a sub–3.0 mm incision to SIA.
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