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L. Zheng, J.C. Merriam; The Effect of Incisions for Cataract on the Major Axis of Corneal Curvature . Invest. Ophthalmol. Vis. Sci. 2005;46(13):775.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the difference in effect on the major axis of corneal curvature of incisions for cataract. Methods: This is a retrospective study of 1123 eyes operated for cataract by a single surgeon. The incisions reviewed include extracapsular cataract extraction (ECCE), a 6 mm superior scleral tunnel (6Sup), a 3 mm superior scleral tunnel (3Sup), a 3 mm temporal scleral tunnel (3Temp), 3.5 mm temporal corneal incision (3Cor), and a 2.6 mm corneal incision (2.6Cor). Corneal keratometry readings before and after surgery were divided into 4 groups: spherical, steeper axis vertical, steeper axis oblique, and steeper axis horizontal. We compared the preoperative major axis of corneal curvature to the final major axis of corneal curvature during the first two years after surgery and used the chi–square test to compare the proportion of patients whose final axis was different than the preoperative axis by type of incision. Results: The proportion of patients whose final major axis of corneal curvature was different than the preoperative major axis was significantly different among ECCE , 6Sup and 3Sup (72%, 47%, 38%; p<0.001) . All of the superior incisions were more likely to change the major axis of corneal curvature than any of the temporal incisions. No significant difference in the proportion of patients with changed axis was detected between the 3.5 and 2.6 mm corneal incisions (28% vs. 30%, p=0.52). However, both corneal incisions were slightly but significantly more likely to change the major axis of corneal curvature than the 3 mm temporal scleral tunnel incision (28% vs. 15%, p=0.008). Conclusions: Contemporary small incisions for phacoemulsification are thought to be astigmatically "neutral". Analysis suggests that small scleral incisions may have less effect on changing the major axis of corneal curvature than small corneal incisions.
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